MPA Vasculitis History and Epidemiology

Microscopic polyangiitis (MPA) vasculitis is a rare type of vasculitis that causes inflammation in the body’s small to medium-sized blood vessels.¹ This inflammation causes decreased blood flow to the body’s organs and tissues. MPA vasculitis typically affects the nerves, kidneys, joints, lungs, and skin. In the United States, the prevalence of MPA vasculitis is about one to three cases per 100,000 people. Currently, it is estimated that fewer than 50,000 people in the US are diagnosed with this condition.²It can occur in anyone but is more common in males of Caucasian descent. The age of onset is usually 50 years.

MPA vasculitis is a type of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis.¹ Antineutrophil cytoplasmic antibodies attack healthy neutrophils and are found in other types of vasculitis including eosinophilic granulomatosis with polyangiitis (EGPA) and granulomatosis with polyangiitis (GPA).³

MPA Vasculitis Diagnosis & Presentation

Patients report varying symptoms of MPA vasculitis.¹ Symptom severity depends on what blood vessels, tissues, or organs are affected. MPA vasculitis may be mild or life-threatening and can develop over a few days to a few months. Symptoms can include^1,2:

fever
fatigue
decreased appetite or pain after eating (if abdominal blood vessels are affected)
nausea, vomiting, and diarrhea
muscle and joint pain
weight loss
increased inflammation after illness or injury
deep venous thrombosis (DVT)

If the kidneys are affected, a patient may be asymptomatic or present with dark or blood-tinged urine.¹ Lesions, rashes, bruising, nodules, and redness may occur on the legs or other areas of the body. If the blood vessels of the eyes are affected, patients may report eye irritation.² Shortness of breath and coughing up bloody sputum may occur if the lungs are affected.¹ Foot or wrist drop, tingling, pain, and weakness may develop if the nerves are affected.

Less common symptoms of MPA vasculitis include²:

abnormal retinal shape
arrhythmia, heart failure, or pericarditis
arthritis
cutis marmorata (reddish-blue discoloration of skin caused by blood pooling in the capillaries)
episcleritis (inflammation of the tissue covering of the sclera)
nosebleeds
gangrene
pancreatitis
uveitis

Diagnostic Workup

A physical exam, comprehensive medical history, and the following tests may aid in diagnosing MPA vasculitis¹:

blood tests for ANCA, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP)
chest x-ray (to show changes in the lungs due to MPA)
computed tomography (CT) and magnetic resonance imaging (MRI) to determine if there are any abnormalities in the patient’s organs
urinalysis to check for red blood cells

To confirm the patient’s diagnosis, tissue biopsy of the affected skin, kidney, nerve, muscle, or lung may be performed to check for inflammation.

Differential Diagnosis

Symptoms of other autoimmune diseases may mimic MPA vasculitis and include⁴:

other types of vasculitis (leukocytoclastic vasculitis, GPA, and EGPA)
sarcoidosis
amyloidosis
Goodpasture disease
cryoglobulinemia
glomerulonephritis
polyarteritis nodosa

Drug toxicities that may have similar symptoms to MPA vasculitis include levamisole, ergot alkaloids, amphetamines, and cocaine.⁴ Malignancies, such as lymphomas, carcinomatosis, and atrial myxomas, should be ruled out. Infections, including infective endocarditis, Rocky Mountain spotted fever, widespread fungal infections, or gonococcus, should also be ruled out.

MPA Vasculitis Management (Nonpharmacotherapy and Pharmacotherapy)

Corticosteroids and immunosuppressant drugs are used for both induction and maintenance of remission.⁴ Commonly prescribed immunosuppressants include cyclophosphamide, rituximab, methotrexate, glucocorticoids, azathioprine, and other biologic drugs.

Tavneos (avacopan), a complement 5a receptor antagonist, was approved by the US Food and Drug Administration in October 2021.^1,5 It may be used as an adjunctive treatment along with steroid treatment.

Patients with a milder form of the disease may be given prednisone plus methotrexate or rituximab alone.⁴ Those with more severe disease may need 1.5 to 2 mg/kg/day of cyclophosphamide plus 1mg/kg/day of prednisone for induction. Plasmapheresis may be needed for patients with alveolar hemorrhage. The induction stage of treatment may last two to six months.

For maintenance, 2 mg/kg/day of azathioprine may be given for up to 12 months followed by a reduction in dose to 1.5 mg/kg/day.⁴ Methotrexate may be given for 12 to 24 months at a dose of 0.3 mg/kg once a week. The dosage of methotrexate may be increased by 2.5 mg per week up to a maximum of 20 mg/week. A 10 mg dose of prednisone per day or every other day may be continued as needed. Prophylaxis against Pneumocystis jirovecii with sulfamethoxazole/trimethoprim may also be needed.

Monitoring Side Effects, Adverse Events, and Drug-Drug Interactions

Since the medications used to treat MPA vasculitis suppress the immune system, prevention of infection is critical.¹ Eligible patients should be advised to get vaccinated against the flu, pneumonia, and shingles.

Side effects to look out for with prednisone use include osteoporosis and avascular necrosis of the bone, glaucoma, cataracts, diabetes, and changes in electrolytes.⁴ Methotrexate reactions can include liver toxicity, pneumonitis, and bone marrow suppression. Cyclophosphamide toxicities can include myelodysplasia, hemorrhagic cystitis, bladder cancer, and bone marrow suppression.

Rituximab carries a boxed warning about progressive multifocal leukoencephalopathy, potentially fatal infusion reactions, severe skin reactions, including Stevens-Johnson syndrome, and reactivation of hepatitis B virus.⁶

Patients should be advised to keep all medical appointments and discuss any new symptoms or side effects with their physician.¹ Routine labs and imaging studies may help detect relapse.

Approximately 90% of patients who receive proper treatment will improve and about 75% of patients will go into remission.^{4 The five-year survival rate of MPA vasculitis is 75% likely due to renal impairment at disease onset.}

References

Microscopic polyangiitis. Vasculitis Foundation. n.d. Accessed September 22, 2022.
National Center for Advancing Translational Sciences. Microscopic polyangiitis. National Institutes of Health.. Last updated November 8, 2021. Accessed September 22, 2022.
National Library of Medicine. Antineutrophil cytoplasmic antibodies (ANCA) test. Medline Plus. Last updated March 2, 2021. Accessed September 22, 2022.
Jain V, Tiwari V. Microscopic Polyangiitis. In: StatPearls. NCBI Bookshelf version. StatPearls Publishing: 2022.
U.S. Food and Drug Administration. Tavneos (avacopan) capsules, for oral use. Last updated October 2021. Accessed September 23, 2022.
U.S. Food and Drug Administration. Rituxan (rituximab) injection, for intravenous use. Last updated December 2021. Accessed September 22, 2022.

Author Bio

Jen Seabright, PharmD, is a freelance medical writer in Pittsburgh, PA.