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• How do we Diagnose Vasculitis?
• Skin Biopsy
• Kidney Biopsy
• Sural Nerve Biopsy
• Temporal Artery Biopsy
• Lung Biopsy
• Brain Biopsy
• Abdominal Angiogram
• Central Nervous System Angiogram
• Other Useful Tests

How do we diagnose Vasculitis?

Patients with vasculitis learn that making the diagnosis is sometimes quite difficult. Many endure numerous doctors’ visits, tests, and hospitalizations before the pieces of the puzzle are assembled. The diagnosis of vasculitis usually requires a biopsy of an involved organ (skin, kidney, lung, nerve, temporal artery). This allows us to ‘see’ the vasculitis by looking under a microscope to see the inflammatory immune cells in the wall of the blood vessel. Although, making a diagnosis of vasculitis can be quite involved, this is very important for two main reasons:

# ONE:  Vasculitis has many MIMICKERS (other diseases that have similar features but require different treatments). It is important to rule out other causes of vascular inflammation, other than a primary autoimmune condition as the management could be different.

# TWO:  The treatments for vasculitis itself involve substantial risk. No physician should prescribe such treatment without making every effort to secure a firm diagnosis.

Blood tests, X–rays, and other studies may suggest the diagnosis of vasculitis, but often the only way to clinch the diagnosis is to biopsy  involved tissue, examine the tissue under the microscope in consultation with a pathologist (ideally one experienced at examining biopsies in vasculitis), and find the pathologic hallmarks of the disease.

If a patient’s symptoms, physical examination, and diagnostic testing suggest involvement of a particular organ, one of the procedures below may be used to confirm (or exclude) the diagnosis of vasculitis:

1. Skin Biopsy: One of the least invasive ways of making the diagnosis. A minor procedure performed under local anesthesia. The wound is closed with 1–2 stitches that are removed 7–10 days later.

The correct diagnosis of PAN (polyarteritis nodosa) was not confirmed by this biopsy because the biopsy was not deep enough. The biopsy specimen contains only the epidermis and superficial dermis. PAN classically affects medium–sized arteries located in the deep dermis.

In contrast to the biopsy above, the skin biopsy below was deep enough to include the deep dermis as well as some subcutaneous fat.

The white, oval–shaped areas are fat lobules. Just superficial to the subcutaneous fat, within the deep dermis, an inflamed medium–sized vessel is evident.

2. Kidney Biopsy: A kidney biopsy will be performed if there is evidence of kidney involvement by vasculitis (red blood cells or protein in the urine, for example). This procedure is done under local anesthesia while the kidney is visualized by ultrasound. Because of the small but significant risk of bleeding after this procedure, patients are usually monitored in the hospital for 24 hours after the biopsy.

3. Sural Nerve Biopsy: The sural nerve is a sensory nerve over the lateral aspect of the foot. Under local anesthesia in an operating room, a surgeon removes a small piece of the nerve, usually along with a piece of the adjacent muscle (the gastrocnemius). Because the sural nerve does not innervate muscles (remember: it is a sensory nerve, not a motor nerve), the patient does not lose any strength on the side of the foot and lower leg. There maybe, however, some residual numbness on the side of the foot. Patients generally tolerate this numbness well (if the vasculitis has involved the nerve severely enough, some patients already have numbness in that region).

4. Temporal Artery Biopsy: Performed to diagnose Giant Cell Arteritis, also known as Temporal Arteritis, because the temporal artery is often involved. The temporal artery courses up the temples, just in front of the ears. The biopsy, done under local anesthesia, is performed by making a small incision just above the hairline (sometimes shaving a small area of hair is required). The procedure is extremely well–tolerated by patients. Within several weeks, there is usually little or no sign that a biopsy was done. Complications of temporal artery biopsies are extremely rare. Sometimes, to increase the diagnostic yield, both temporal arteries (i.e., the ones on each side of the head) are biopsied.

5. Lung Biopsy : Often the best way to make a diagnosis of vasculitis that involves the lungs, such as granulomatosis with polyangiitis (GPA). A lung biopsy may be performed in one of two ways: 1) open lung biopsy, a sizable surgical procedure; or 2) thoracoscopic lung biopsy, a less invasive but still significant procedure. Even a thoracoscopic biopsy usually requires at least 48 hours in the hospital and the temporary placement of a chest tube to permit the lung to re–expand.

6. Brain Biopsy: Often necessary to confirm the diagnosis of Central Nervous System (CNS) Vasculitis. This is usually performed on the non–dominant side of the patient’s brain (that is, if the patient is right–handed — and therefore “left–brained” — the biopsy is performed on the right side of the brain). Biopsy of the brain’s covering, the meninges, is usually performed at the same time.

7. Angiogram / angiography: Angiography is helpful in the diagnosis of Polyarteritis Nodosa (PAN). Similar to a heart catheterization,  after inserting a catheter into a large artery in the leg and advancing the catheter into the aorta, radiographic dye is injected into blood vessels supplying the gastrointestinal tract. In the proper clinical setting, the detection of aneurysms (small outpouchings of blood vessel walls) is diagnostic of PAN. This gives an accurate picture of the luminal (inside) anatomy of blood vessels.

8. Central nervous system angiogram Frequently part of the “work–up” of CNS vasculitis. The procedure is identical to an abdominal angiogram, except the catheter is advanced all the way up to the large vessels supplying the head and neck (for example, the carotid arteries). On angiography, CNS vasculitis is characterized by “beading” (dilated areas alternating with narrowing of the blood vessels). A strikingly abnormal angiogram may eliminate the need for a brain biopsy.

9. Other Useful Tests: There are many other tests that are helpful in the diagnosis of vasculitis, or in evaluating the activity of the disease:

• Erythrocyte sedimentation rate (ESR)
• C–reactive protein (CRP)
• Urinalysis
• CT Scan
• ANCA tests

Erythrocyte sedimentation rate (ESR):  Also known as the “sed rate”, for short. This is an old but useful test first employed by the ancient Greeks as a test for pregnancy. It is important to note that there are several influences on the ESR such as anemia and hypergammaglobulinemia which may have nothing to do with an inflammatory state.

C–reactive protein (CRP): CRP is a protein produced by the liver in response to inflammation within the body.

Urinalysis: Many forms of vasculitis affect the kidneys. A simple way of determining whether or not the kidneys are involved is to perform a urinalysis. By performing checks for several indicators of inflammation in a patient’s urine, the physician may determine if inflammation is present within the kidneys. These indicators include:

• Protein (“proteinuria”)
• Red blood cells (“hematuria”)
• Clumps of red blood cells (“casts”)

Pictured below is a urine specimen from a patient with Wegener’s granulomatosis and glomerulonephritis (inflammation in the kidneys).

From another Wegener’s granulomatosis patient’s urinalysis, “blebs” (identified by white arrows) protrude from the surface of the red blood cells that have been damaged in transit through the kidney.

CT Scan (a CAT scan, or computed tomography) — A type of radiology test that permits a non-invasive, cross–sectional view of a patient’s anatomy. On the illustration below (a chest CT scan from a patient with GPA), the view is up (looking toward the patient’s head, from his or her feet). The heart is the white, rounded object in the upper center of the picture. The black regions are the patient’s lungs. The large spot in the left lung (corresponding to the patient’s right lung) is a nodule caused by GPA. Other smaller nodules are also evident.

 

MRI / MRA: MRI is another imaging modality that can be useful for diagnosing and following systemic vasculitis; particularly large vessel vasculitis. MRI allows for visualization of the vessel wall. In vasculitis, the vessel wall may be thickened or edematous.

ANCA tests — ANCA is an abbreviation (acronym) for anti–neutrophil cytoplasmic antibodies. These antibodies are found in the blood of patients with several different types of vasculitis, including Wegener’s Granulomatosis, Microscopic Polyangiitis, and the Churg–Strauss Syndrome. ANCAs and their association with vasculitis were recognized in the mid–1980s, and their use has become increasingly widespread since the 1990s. ANCAs are detected by a simple blood test. These antibodies are directed against the cytoplasm (the non–nucleus part) of white blood cells. Their precise role in the disease process remains uncertain but is a topic of considerable research interest. ANCAs come in two primary forms: 1) the C–ANCA [C stands for cytoplasmic] and, 2) the P–ANCA [P stands for perinuclear]. C–ANCAs have a particularly strong connection to Wegener’s Granulomatosis (up to 80% of patients – and possibly more of those with active disease – have these antibodies). When C–ANCAs are present in the blood of a patient with symptoms or signs suggesting Wegener’s, the likelihood of the diagnosis increases considerably. Because of the long list of other conditions that are sometimes associated with ANCAs, however, in most cases it is still VERY IMPORTANT to biopsy an organ involved by vasculitis to verify the diagnosis.

 

All information contained within the Johns Hopkins Vasculitis Center website is intended for educational purposes only. Visitors are encouraged to consult other sources and confirm the information contained within this site. Consumers should never disregard medical advice or delay in seeking it because of something they may have read on this website.

• First Description
• Who gets Rheumatoid Vasculitis (the “typical” patients)?
• Classic symptoms of Rheumatoid Vasculitis
• What causes Rheumatoid Vasculitis?
• How is Rheumatoid Vasculitis diagnosed?
• Treatment and Course of Rheumatoid Vasculitis
• What’s new in Rheumatoid Vasculitis?

First Description

Rheumatoid Vasculitis (RV) is an unusual complication of longstanding, severe rheumatoid arthritis. The active vasculitis associated with rheumatoid disease occurs in about 1% of this patient population.

RV is a manifestation of “extra-articular” (beyond the joint)rheumatoid arthritis and involves the small and medium-sized arteries in the body. In many of its disease features, RV resembles polyarteritis nodosa.

Other common extra-articular manifestations of rheumatoid arthritis, such as inflammation in the sac surrounding the heart (pericarditis), inflammation in the lining of the lungs (pleuritis), and interstitial lung disease (resulting in fibrosis or scarring of the lungs).

Who gets Rheumatoid Vasculitis? A typical patient

RV can affect a person from any ethnic background, either gender, and from any age group. However, more often than not, the typical patient has long-standing rheumatoid arthritis with severe joint deformities from the underlying arthritis. Although the arthritis has usually led to significant joint damage, at the onset of RV the joint disease is paradoxically quiet.

Figure: Patient with joint damage from rheumatoid arthritis. Note the bulbous swelling of some knuckles and lateral (ulnar) deviation of the fingers.

Classic symptoms of Rheumatoid Vasculitis

RV has many potential signs and symptoms. The manifestations of RV can involve many of the body’s different organ systems, including but not limited to the skin, peripheral nervous system (nerves to the hands and feet) , arteries of the fingers and toes causing digital ischemia, and eyes with scleritis. Scleritis (inflammation of the white part of the eye) commonly occurs in the setting of RV. This ocular complication requires urgent treatment with immunosuppressive medications.

Figure: Digital ischemia – this image shows a blood flow deficiency in the tip of the finger caused by an obstruction of the digital artery.

Figure: Scleritis – Inflammation of the sclera (the white of the eye) causing redness, light sensitivity and pain.

In addition, generalized symptoms such as fever and weight loss are common.

As is true with other forms of vasculitis that involve the skin, cutaneous lesions can erupt on various areas of the body in RV, with a predilection for the lower extremities. Typical findings include ulcers concentrated near the ankles.

Figure: Cutaneous ulcer – an open skin sore caused by an obstruction of the small blood vessels in the superficial ulcers or obstruction of medium vessels in a deeper ulcer.

Small nail fold infarcts (small spots around fingernail) can

occur in rheumatoid arthritis

but these do not necessarily signify the presence of systemic vasculitis and do not necessitate a change in rheumatoid arthritis treatment.

Nerve damage can cause foot or wrist drop, known in medical terminology as “mononeuritis multiplex”. The images below show a patient with a right wrist drop and a patient with right foot drop. This condition, which may be significantly disabling, is often preceded by a change in sensation in the same area (numbness, tingling, burning, or pain). These abnormal sensations can progress to muscle weakness, focal paralysis, and eventually to muscle wasting. Recovery from this condition, caused by nerve infarction, can take months. In some cases, recoveries from mononeuritis multiplex are incomplete.

Figures of drop wrist and drop foot (courtesy of the University of North Carolina)

(Video of drop foot viewable on our Microscopic Polyangiitis page under classic symptoms.)

Laboratory Tests

Most laboratory findings in RV – for example, elevations in the erythrocyte sedimentation rate or C-reactive protein – are non-specific, and reflect the presence of a generalized inflammatory state. Hypocomplementemia, anti-nuclear antibodies (ANA), and atypical anti-neutrophil cytoplasmic antibodies (ANCA) are common. Rheumatoid factor levels are usually extremely elevated. However, there is no definitive laboratory test for RV short of a tissue biopsy. The diagnosis must usually be made using a combination of history, physical examination, pertinent laboratory investigations, specialized testing (e.g., nerve conduction studies), and sometimes a tissue biopsy.

Because the treatment implications for RV are major, any diagnostic uncertainty must be met with definitive approaches to establishing the diagnosis. This usually involves biopsy of an involved organ. Deep skin biopsies (full-thickness biopsies that include some subcutaneous fat) taken from the edge of ulcers are very useful in detecting medium-vessel vasculitis. Nerve conduction studies help identify involved nerves for biopsy. Muscle biopsies (e.g., of the gastrocnemius muscle) should be performed at the same time as nerve biopsies, to increase the chance of finding changes characteristic of vasculitis. Imaging studies have no consistent role in the evaluation of RV, although sometimes angiography of the gastrointestinal tract is useful.

What Causes Rheumatoid Vasculitis?

The cause of RV is unknown, but given the prominence of immune components and the pathologic changes in involved blood vessels, an auto-immune process is suggested.

How is Rheumatoid Vasculitis diagnosed?

Most laboratory findings in RV – for example, elevations in the erythrocyte sedimentation rate or C-reactive protein are non-specific, and reflect the presence of a generalized inflammatory state. Hypocomplementemia, anti-nuclear antibodies (ANAs), and atypical anti-neutrophil cytoplasmic antibodies (atypical ANCAs) are common. Rheumatoid factor levels are extremely elevated, as a rule. However, there is no definitive laboratory test for RV short of a tissue biopsy. The diagnosis must usually be made by the combination of history, physical examination, pertinent lab work, other specialized testing (e.g., nerve conduction studies), and sometimes even a tissue biopsy is required.

The diagnosis of RV should be considered in any rheumatoid arthritis patient who develops new constitutional symptoms, skin ulcerations, decreased blood flow to the fingers or toes, symptoms of a sensory or motor nerve dysfunction (numbness, tingling, focal weakness); or any inflammation of the lining around the heart or lungs (pericarditis or pleurisy/pleuritis).

Patients with a history of joint-destructive rheumatoid arthritis are at an increased risk for infection. Therefore, when a rheumatoid arthritis patient presents with a new onset of non-specific systemic complaints an infection must first be eliminated. Patients with rheumatoid arthritis typically have immune systems that are disordered from previous immunosuppression and underlying disease (e.g., joint damage). This patient population, therefore, is at higher risk of infection.

The differential diagnosis of RV includes:

• Cholesterol embolization syndromes, in which a piece of cholesterol breaks off of a plaque, may cause digital ischemia (blood flow obstruction to a finger or toe), and a host of other symptoms that mimic vasculitis.
• Diabetes mellitus is another major cause of mononeuritis multiplex, but multiple mononeuropathies occurring over a short period of time are unusual in diabetes.
• Many clinical features of RV mimic those of polyarteritis nodosa, cryoglobulinemia, and other forms of necrotizing vasculitis. Therefore they too should be considered in this setting.

Because the treatment implications for RV are major, any diagnostic uncertainty must be met with a definitive approach to establishing the diagnosis. As alluded to earlier, this usually involves the biopsy of an involved organ. Deep skin biopsies (full-thickness biopsies that include some subcutaneous fat) taken from the edge of ulcers are very useful in detecting medium-vessel vasculitis. Nerve conduction studies help identify involved nerves for biopsy. Muscle biopsies (e.g., of the gastrocnemius muscle) should be performed at the same time as nerve biopsies, to increase the chance of finding changes characteristic of vasculitis. Imaging studies have no consistent role in the evaluation of RV, although sometimes angiography of the gastrointestinal tract is useful.

Normally, the cells of the blood vessel wall would be fewer in number (less thick) and the lumen (larger red area) would be larger. The arrow points (Figure 6, left) to an inflamed blood vessel found on a muscle biopsy. The globular pink areas are muscle fibers.

Treatment and Course of Rheumatoid Vasculitis

Therapy should reflect the severity of organ involvement. Prednisone or other steroid therapies are often the first line of treatment. Optimizing treatment of the underlying rheumatoid arthritis is also essential, therefore medications such as methotrexate or tumor necrosis factor inhibitors may be employed. In the setting of impending damage to major organs such as the eyes, a peripheral nerve, the gastrointestinal tract, or of a severe skin ulceration, cyclophosphamide is usually warranted.

What’s New in Rheumatoid Vasculitis?

Compared to other forms of vasculitis, there has been relatively little research in recent years on the specific entity of RV. The lack of similarity in available reports on RV and discrepancies in case definitions have created challenge to building standard approaches to the diagnosis and treatment of this condition. There is some evidence that the incidence of RV has decreased over the past several decades, perhaps because of better treatment of the underlying rheumatoid arthritis.

Vasculitis Center Doctors

Collaborators

Vasculitis can involve virtually any organ system within the body. Hence, our Vasculitis Center maintains close collaborative relationships with experts from other specialties. The Vasculitis Center includes collaborators from several medical disciplines who help provide the highest level of care for our patients. They have extensive experience managing vasculitis within their subspecialty and work closely with the Physicians in the Vasculitis Center to provide comprehensive care for our patients:

Otolaryngology (ENT):

Our ENT team includes specialists in inflammatory sinus disease, sensorineural hearing loss, and chronic middle ear disease. We are pleased to also have a Doctor of Audiology, Dr. Dinkes, who specializes in inflammatory process on our team as well.

• Dr. Jean Kim (sinus disease, middle ear manifestations)
• Dr. Alexander Hiller (upper airway disease)
• Dr. Roni Dinkes (audiology)

Neuro-ophthalmology:

• Dr. Andrew Carey

Endocrinology / Osteoporosis:

• Dr. Han Na Kim

What is IVIG/SCIG?

Intravenous immunoglobulin (IVIG) is a therapy consisting of pooled antibodies (immunoglobulin) obtained from healthy donors that is given as an infusion by vein. This same therapy can also be given as a subcutaneous injection (SCIG) rather than an intravenous one.

How does it work?

IVIG and SCIG are often used to treat patients with immunodeficiency syndromes, which are genetic or acquired conditions that lead to low immunoglobulin levels. For these patients, IVIG/SCIG provide the protective effect of antibodies that they otherwise lack.

In treating vasculitis, we sometimes encounter the need for IVIG/SCIG due to the use of Rituximab – a drug that targets B cells. In some patients, the long-term use of rituximab may lead to an acquired deficiency of immunoglobulins. By combining IVIG/SCIG with rituximab, we are able to continue to provide patients with the immunosuppressive benefit of rituximab, while compensating for the increased risk of infection by giving IVIG/SCIG.

How is IVIG/SCIG given?

IVIG is often given as a home infusion. SCIG is given as a subcutaneous injection. These treatments are generally given once per month.

Side effects:

These treatments carry a risk of blood clot, renal injury, and headaches. IVIG constitutes a large fluid challenge, and therefore may not be appropriate for patients with heart or kidney failure.

• First Description
• Who gets Microscopic Polyangiitis (the “typical” patients)?
• Classic symptoms of Microscopic Polyangiitis
• Forms of vasculitis similar to Microscopic Polyangiitis
• What causes Microscopic Polyangiitis?
• How is Microscopic Polyangiitis diagnosed?
• Treatment and Course of Microscopic Polyangiitis

First Description

The first description of a patient with the illness now known as microscopic polyangiitis (MPA) appeared in the European literature in the 1920s. The concept of this disease as a condition that is separate from polyarteritis nodosa (PAN) and other forms of vasculitis did not begin to take root in medical thinking, however, until the late 1940s. Even today, some confusing terms for MPA (e.g., “microscopic poly arteritis nodosa ” rather than “microscopic poly angiitis ”) persist in the medical literature. Confusion regarding the proper nomenclature of this disease led to references to “microscopic polyarteritis nodosa” and “hypersensitivity vasculitis” for many years. In 1994, The Chapel Hill Consensus Conference recognized MPA as its own entity, distinguishing it in a classification scheme clearly from PAN, granulomatosis with polyangiitis (GPA, formerly Wegener’s), cutaneous leukocytoclastic angiitis (CLA), and other diseases with which MPA has been confused with through the years.

Much of the explanation for the difficulty in separating MPA from other forms of vasculitis has stemmed from the numerous areas of overlap of MPA with other diseases. MPA, PAN, GPA, and CLA  and other disorders all share a variety of features but possess sufficient differences as to justify separate classifications.

Who gets Microscopic Polyangiitis? A typical patient

MPA can affect individuals from all ethnic backgrounds and any age group. In the United States, the typical MPA patient is a middle-aged white male or female, but many exceptions to this exist. The disease may occur in people of all ages, both genders, and all ethnic backgrounds.

Classic symptoms of Microscopic Polyangiitis

Many signs and symptoms are associated with MPA. This disease can affect many of the body’s organ systems including (but not limited to) the kidneys, nervous system (particularly the peripheral nerves, as opposed to the brain or spinal cord), skin, and lungs. In addition, generalized symptoms such as fever and weight loss are very common.

The FIVE most common clinical manifestations of MPA are:

1. Kidney inflammation (~ 80% of patients).
2. Weight loss (> 70%).
3. Skin lesions (> 60%).
4. Nerve damage (60%).
5. Fevers (55%).

Kidney Inflammation

Inflammation in the kidneys, known as glomerulonephritis, causes blood and protein loss through the urine. This process can occur either slowly or very rapidly in the course of the disease. Patients with kidney inflammation may experience fatigue, shortness of breath, and swelling of the legs.

The image below is from a urinalysis of a patient with kidney inflammation. When MPA is active, red blood cells will form a clump or “cast” (bracketed in white) within the tubules of inflamed kidneys. These “casts” pass through the renal system and may be viewed under the microscope in a patient’s urine.

Constitutional Symptoms

Weight loss, fevers, fatigue, and malaise are part of a collection of complaints regarded as “constitutional” symptoms. Constitutional complaints are a common finding in patients with MPA, because the disorder is a systemic disease confining itself generally not to one specific organ system but rather broadly affecting a patient’s “constitution”.

Skin lesions

Skin lesions in MPA, as in other forms of vasculitis that involve the skin, can erupt on various areas of the body. The lesions tend to favor the “dependent” areas of the body, specifically the feet, lower legs and, in bed-ridden patients, the buttocks. The skin findings of cutaneous MPA include purplish bumps and spots pictured below (palpable purpura).

These areas range in size from several millimeters in diameter to coalescent lesions that are even larger. Skin findings in MPA may also include small flesh-colored bumps (papules); small-to-medium sized blisters (vesiculobullous lesions); or as small areas of bleeding under the nails that look like splinters (pictured below), hence the name splinter hemorrhages.

Peripheral nervous system

Damage to peripheral nerves (i.e., nerves to the hands and feet, arms and legs) results from inflammation of the blood vessels that supply the nerves with nutrients. Inflammation in these blood vessels deprives the nerves of their nutrients, leading to nerve infarction (tissue death). Multiple nerve involvement that is characteristic of vasculitis is known as “mononeuritis multiplex”. This condition is frequently associated with wrist or foot drop: the inability to extend the hand “backwards” at the wrist or to flex the foot upward toward the head at the ankle joint. If the condition is caused by nerve deterioration associated with vasculitis, unfortunately, surgery is not a treatment option due to the nerve infarcton (tissue death).

Neurologic symptoms resulting from peripheral nerve damage may also include numbness or tingling in the arm, hand, leg, or foot. Over time, muscle wasting (pictured below) that is secondary to the nerve damage may result from damage caused by vasculitis.

Pictured:

The hand on the left (the patient’s right hand) is normal, displaying normal muscle bulk of the areas between the fingers.  In contrast, the hand on the right (the patient’s left) shows wasting of the muscle in the web space between the thumb and first finger, leading to a hollowed-out, bowl-like appearance of that area.  The consequence of this muscle wasting is that the patient is unable to grasp objects between his thumb and fingers (i.e., has a weak pinch) and his hand grip is weak.

Lungs

Lung involvement can be a dramatic and life-threatening manifestation of MPA. When lung disease takes the form alveolar hemorrhage – bleeding from the small capillaries that are in contact with the lungs’ microscopic air sacs – the condition may quickly pose a threat to the patient’s respiratory status (and therefore to the patient’s life). Alveolar hemorrhage (pictured below), which is frequently heralded by the coughing up of blood, occurs in approximately 12% of patients with MPA .

Another common lung manifestation of MPA is the development of non-specific inflammatory infiltrates, identifiable on chext x-rays or computed tomography (CT scans) of the lung.

Eyes, Muscles, and Joints

Organs that also merit mention in discussions of MPA include the eyes, muscles, and joints. Intermittent irritation of the eye (resembling “pinkeye”) that is caused by either conjunctivitis or episcleritis may be an early disease manifestation or a sign of a disease flare. Occasionally other types of inflammation (e.g., uveitis) are also observed in MPA. Muscle or joint pains (known to clinicians as “myalgias” or “arthralgias”, respectively) are common complaints in MPA, generally accompanying the types of constitutional symptoms mentioned above. Arthritis (inflammation of the joints accompanied by swelling) can also be observed in MPA. Joint complaints in MPA and related forms of vasculitis tend to migrate from one joint to another – one day involving the left ankle, the next day the right wrist, the third day a shoulder, for example.

Forms of vasculitis similar to Microscopic Polyangiitis

The similarities and differences between MPA, GPA, and PAN are highlighted in the table below.

	MPA	GPA	PAN
BLOOD VESSEL SIZE	Small to Medium	Small to Medium	Medium
BLOOD VESSEL TYPE	Arterioles to venules, And sometimes Arteries and veins	Arterioles to venules, And sometimes Arteries and veins	Muscular Arteries
GRANULOMATOUS INFLAMMATION	NO	YES	NO
LUNG SYMPTOMS	YES1	YES1	NO
GLOMERULONEPHRITIS	YES	YES	NO
RENAL HYPERTENSION	NO	NO	YES
MONONEURITIS MULTIPLEX	COMMON	OCCASIONAL	COMMON
SKIN LESIONS	YES2	YES2	YES2
GI SYMPTOMS	NO	NO	YES3
EYE SYMPTOMS	YES4	YES4	NO
ANCA-POSITIVITY	75%	65-90%	NO
CONSTITUTIONALSYMPTOMS	YES5	YES5	YES5
NECROTIZING TISSUE	YES	YES	YES
MICROANEURYSMS	RARELY	RARELY	TYPICAL

¹ Pulmonary capillaritis in MPA and nodules or cavitary lesions in WG

²MPA can have small blood vessel skin lesions as mentioned above, similar to GPA or medium blood vessel lesions similar to PAN (livedo reticularis, nodules, ulcers, and digital gangrene)

³Stomach pain after meals

⁴MPA eye complications are typically milder than those of GPA, but serious

ocular problems including necrotizing scleritis can occur

⁵Constitutional symptoms include weight loss, fevers, joint and muscle aches, and malaise.

What Causes Microscopic Polyangiitis?

The cause of MPA is not known. However, enough is known about a few types of vasculitides that allow us to describe in general terms how MPA affects the body. MPA is clearly a disorder that is mediated by the immune system; the precise events leading to the immune system dysfunction (hyperactivity), however, remain unclear. Many elements of the immune system are involved in this process: neutrophils, macrophages, T and B lymphocytes, antibodies, and many, many others.

Because MPA is often associated with anti-neutrophil cytoplasmic antibodies (ANCA), antibodies directed against certain constituents of white blood cells (WBCs), the disease is often termed an “ANCA-associated vasculitis”, or AAV. ANCA, discovered in 1982, act against certain specific (and naturally occurring) enzymes in the body residing within the neutrophils and the macrophages, all of which are members of the WBC family. The result of the interactions of ANCA with their target proteins is an increase in the destruction of WBCs at the sites of disease and the release of white blood cell enzymes within blood vessel walls, causing the damage to blood vessels. In MPA, the ANCA are directed generally against to specific proteins: myeloperoxidase (MPO) and proteinase 3 (PR3).

How is Microscopic Polyangiitis diagnosed?

Blood is taken to detect any ANCA levels, if MPA is suspected. In addition, an erythrocyte sedimentation rate (ESR or “sed rate”) and C-reactive protein (CRP) are usually ordered. Both of these tests are elevated in many different types of inflammation and are not specific to MPA or any particular disease. The ESR and CRP, known as “acute phase reactants”, are often sensitive indicators of the presence of active disease. In and of themselves, however, elevations in acute phase reactants are not sufficient to justify additional treatment.

A carefully analyzed urine specimen should be obtained at the initial visit (and every follow-up visit!) to maintain vigilance for either the development or the progression of kidney involvement.

A computed tomography (CT) scan of the chest may also be performed to detect the presence of lung involvement. A tissue biopsy may be needed to make the diagnosis of MPA, and is taken from an organ that seems to be involved at the time. Sometimes an electromyography/nerve conduction (EMG/NCV) study may need to be done to identify a site for biopsy or to detect findings consistent with a mononeuritis multiplex (see classic symptoms section above). Tissues that might be biopsied are kidney, skin, nerve, muscle, and lung.

Pictured: a biopsy of the gastrocnemius muscle, performed in a 69 year–old man with microscopic polyangiitis. A blood vessel within the muscle shows an intense inflammatory infiltrate with destruction of the blood vessel wall, confirming the diagnosis of vasculitis.

Treatment and Course of Microscopic Polyangiitis

A steroid (usually prednisone) in combination with a cyclophosphamide (CYC) or rituximab is typically the first combination of medications to be prescribed.  After control of the disease – usually around 4 – 6 months of treatment maintenance therapy will be used to keep the disease in remission. This will vary between patients. Prednisone may be discontinued after approximately 6 months.