Introduction
Background
Microscopic polyangiitis (MPA) is vasculitis of small vessels. It was initially considered as a microscopic form of polyarteritis nodosa (PAN). In 1990, the American College of Rheumatology developed classification criteria for several types of systemic vasculitis but did not distinguish between polyarteritis nodosa and microscopic polyarteritis nodosa. In 1994, a group of experts held an international consensus conference in Chapel Hill, North Carolina to attempt to redefine the classification of small vessel vasculitides.
The vasculitis in small vessels, including arterioles, capillaries, and venules, that is characteristic of MPA is absent in polyarteritis nodosa, making this the proposed distinguishing feature of the two conditions. MPA, Wegener granulomatosis, and Churg-Strauss syndrome comprise a category of small-vessel vasculitis related to antineutrophil cytoplasmic antibodies (ANCAs) and are characterized by a paucity of immune deposits. MPA and Wegener granulomatosis seem to be part of a clinical spectrum. However, the absence of granuloma formation and sparing of the upper respiratory tract are features of MPA. These features help to distinguish MPA from Wegener granulomatosis, although the two conditions are occasionally difficult to distinguish.
Pathophysiology
Vasculitis is inflammation of the vessel walls. MPA is characterized by pauci-immune, necrotizing, small-vessel vasculitis without clinical or pathological evidence of necrotizing granulomatous inflammation.
Frequency
United States
The annual incidence is 3.6 cases per million persons. Prevalence is 1-3 cases per 100,000 population.
International
Incidence is approximately 2 cases per 100,000 persons in the United Kingdom and approximately 1 case in 100,000 persons in Sweden.
Mortality/Morbidity
- Renal failure and pulmonary involvement are the major causes of morbidity and mortality.
- With treatment, Falk and Guillevin reported 2- and 5-year survival rates of 75% and 74% respectively.
Race
- In the United States, the disease is more frequent among white persons than black persons.
Sex
- Males are affected slightly more frequently than females.
Age
- The age of onset is approximately 50 years.
Clinical
History
Symptoms of microscopic polyangiitis (MPA) include the following:
- Constitutional symptoms
- Fever (55%)
- Malaise, fatigue, flulike syndrome
- Myalgia (48%)
- Weight loss (72%)
- Skin manifestations - Skin rash (50%)
- Pulmonary manifestations
- Hemoptysis (11%)
- Dyspnea
- Cough
- Cardiovascular manifestations – Chest pain, symptoms of heart failure
- Gastrointestinal involvement
- Gastrointestinal bleeding
- Abdominal pain
- Nervous system manifestations
- More commonly, peripheral nervous system involvement manifesting as mononeuritis multiplex (57%)
- CNS involvement manifesting as seizures (11%)
- Arthralgias (10-50%)
- Testicular pain (2%)
- Ocular manifestations (1%)
- Red eye
- Ocular pain
- Decreased visual acuity
- Symptoms of sinusitis (1%)
Physical
The physical examination findings include the manifestations of specific organ system involvement. A dermato-pulmonary-renal syndrome is the feature of the disease.- Fever
- Skin involvement
- Leukocytoclastic angiitis and its palpable purpura (Leukocytoclastic purpura could be a manifestation of the systemic vasculitides or could be a stand-alone skin disorder.)
- Palpable purpura (41%)
- Livedo reticularis (12%)
- Skin ulcerations
- Necrosis and gangrene
- Necrotizing nodules
- Urticaria
- Digital ischemia (7%)
- Urticaria - Vasculitis-associated urticaria that lasts longer than 24 hours
- Lower respiratory system
- Pulmonary rales
- Respiratory distress
- Upper respiratory tract - Sinusitis less frequent than in Wegener granulomatosis
- Cardiovascular system
- Hypertension (34%)
- Signs of cardiac failure (17%)
- Myocardial infarction (2%)
- Pericarditis (10%)
- Gastrointestinal system
- Gastrointestinal bleeding
- Bowel ischemia and perforation
- Pancreatitis
- Ocular involvement (1%)
- Retinal hemorrhage
- Scleritis
- Uveitis
- Renal involvement - Signs of uremia in advanced renal failure
- Musculoskeletal system
- Synovitis
- Arthritis
- Nervous system
- Mononeuritis multiplex - Most frequent neurologic manifestation of the disease (57%)
- CNS involvement - Includes meningeal vasculitis (11%)
- Other organ vasculitis – Orchitis (2%)
Causes
- Based on current understanding of the inflammatory response, cytokine-mediated changes in the expression and function of adhesion molecules coupled with inappropriate activation of leukocytes and endothelial cells are postulated to be the primary factors influencing the degree and location of vessel damage in the vasculitis syndromes. However, the stimuli that initiate these pathologic inflammatory changes are not well understood.
- ANCA may play a role in the pathogenesis of MPA.
- Case reports have described an association of MPA with medications such as propylthiouracil and with diseases such as primary biliary cirrhosis.
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| References |
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References
Amezcua-Guerra LM, Prieto P, Bojalil R, et al. Microscopic polyangiitis associated with primary biliary cirrhosis: a causal or casual association?. J Rheumatol. Nov 2006;33(11):2351-3.
Falk RJ, Hogan S, Carey TS, Jennette JC. Clinical course of anti-neutrophil cytoplasmic autoantibody-associated glomerulonephritis and systemic vasculitis. The Glomerular Disease Collaborative Network. Ann Intern Med. Nov 1 1990;113(9):656-63. [Medline].
Fries JF, Hunder GG, Bloch DA, et al. The American College of Rheumatology 1990 criteria for the classification of vasculitis. Summary. Arthritis Rheum. Aug 1990;33(8):1135-6. [Medline].
Guillevin L, Durand-Gasselin B, Cevallos R, et al. Microscopic polyangiitis: clinical and laboratory findings in eighty-five patients. Arthritis Rheum. Mar 1999;42(3):421-30. [Medline].
Haubitz M, Koch KM, Brunkhorst R. Cyclosporin for the prevention of disease reactivation in relapsing ANCA-associated vasculitis. Nephrol Dial Transplant. Aug 1998;13(8):2074-6. [Medline].
Jayne D, Rasmussen N, Andrassy K, et al. A randomized trial of maintenance therapy for vasculitis associated with antineutrophil cytoplasmic autoantibodies. N Engl J Med. Jul 3 2003;349(1):36-44. [Medline].
Jayne DR, Gaskin G, Pusey CD, Lockwood CM. ANCA and predicting relapse in systemic vasculitis. QJM. Feb 1995;88(2):127-33. [Medline].
Jennette JC, Falk RJ, Andrassy K, et al. Nomenclature of systemic vasculitides. Proposal of an international consensus conference. Arthritis Rheum. Feb 1994;37(2):187-92. [Medline].
Jennette JC, Falk RJ. Small-vessel vasculitis. N Engl J Med. Nov 20 1997;337(21):1512-23. [Medline].
Jennette JC. Antineutrophil cytoplasmic autoantibody-associated diseases: a pathologist''s perspective. Am J Kidney Dis. Aug 1991;18(2):164-70. [Medline].
Kamesh L, Harper L, Savage CO. ANCA-positive vasculitis. J Am Soc Nephrol. Jul 2002;13(7):1953-60. [Medline].
Langford CA, Talar-Williams C, Sneller MC. Mycophenolate mofetil for remission maintenance in the treatment of Wegener's granulomatosis. Arthritis Rheum. Apr 15 2004;51(2):278-83. [Medline].
Lhote F, Cohen P, Genereau T, et al. Microscopic polyangiitis: clinical aspects and treatment. Ann Med Interne (Paris). 1996;147(3):165-77. [Medline].
Lightfoot RW, Michel BA, Bloch DA, et al. The American College of Rheumatology 1990 criteria for the classification of polyarteritis nodosa. Arthritis Rheum. Aug 1990;33(8):1088-93. [Medline].
Matteson EL. Small-vessel vasculitis. N Engl J Med. Apr 2 1998;338(14):994-5. [Medline].
Nowack R, Gobel U, Klooker P, et al. Mycophenolate mofetil for maintenance therapy of Wegener''s granulomatosis and microscopic polyangiitis: a pilot study in 11 patients with renal involvement. J Am Soc Nephrol. Sep 1999;10(9):1965-71. [Medline].
Reinhold-Keller E, De Groot K, Rudert H, et al. Response to trimethoprim/sulfamethoxazole in Wegener''s granulomatosis depends on the phase of disease. QJM. Jan 1996;89(1):15-23. [Medline].
Ronco P, Verroust P, Mignon F, et al. Immunopathological studies of polyarteritis nodosa and Wegener''s granulomatosis: a report of 43 patients with 51 renal biopsies. Q J Med. 1983;52(206):212-23. [Medline].
Savage CO, Harper L, Adu D. Primary systemic vasculitis. Lancet. Feb 22 1997;349(9051):553-8. [Medline].
Seligman VA, Bolton PB, Sanchez HC. Propylthiouracil-induced microscopic polyangiitis. J Clin Rheumatol. Jun 2001;7(3):170-4.
Sneller MC, Fauci AS. Pathogenesis of vasculitis syndromes. Med Clin North Am. Jan 1997;81(1):221-42. [Medline].
Stegeman CA, Tervaert JW, de Jong PE, Kallenberg CG. Trimethoprim-sulfamethoxazole (co-trimoxazole) for the prevention of relapses of Wegener''s granulomatosis. Dutch Co-Trimoxazole Wegener Study Group. N Engl J Med. Jul 4 1996;335(1):16-20. [Medline].
Watts RA, Jolliffe VA, Carruthers DM, et al. Effect of classification on the incidence of polyarteritis nodosa and microscopic polyangiitis. Arthritis Rheum. Jul 1996;39(7):1208-12. [Medline].
Further Reading
Keywords
microscopic polyangiitis, MPA, small vessel vasculitis, microscopic polyarteritis nodosa, microscopic PAN, small vessel vasculitides, systemic vasculitis, Wegener granulomatosis, Wegener's granulomatosis, Churg-Strauss syndrome, polyarteritis nodosa
