The spectrum of vasculitis: clinical, pathologic, immunologic and therapeutic considerations

Vasculitis is a clinicopathologic process characterized by inflammation and necrosis of blood vessels. Certain disorders have vasculitis as the predominant and most obvious manifestation, whereas others have various degrees of vasculitis in association with other primary disorders. Within the entire spectrum of vasculitis virtually any size or type of blood vessel in any organ system can be involved. Most of the vasculitides can be associated directly or indirectly with immunopathogenic mechanisms. In this regard, immune complex mediation is being increasingly recognized as the underlying mechanism in several of the vasculitides. With clinical, pathologic, and immunologic criteria, certain vasculitic disorders can be clearly recognized and categorized as distinct entities, whereas in others there is an overlap of different diseases within a broader category. In recent years, several of the more serious vasculitides, such as Wegener's granulomatosis and the systemic necrotizing vasculitides of the polyarteritis nodosa group, which formerly had extremely poor prognoses, have been shown to be extraordinarily responsive to chronic low-dose cytotoxic therapy, particularly cyclophosphamide.

Primary pulmonary hypertension: natural history and the importance of thrombosis

A long-term retrospective follow-up study was made of 120 patients (33 male, 87 female patients) with primary pulmonary hypertension--diagnosed by strict clinical and hemodynamic criteria--to obtain a better understanding of the natural history and possible pathogenetic mechanisms of the disease. The mean age at diagnosis was 34 (3 to 64) years, but only 24 patients (21%) remained alive 5 years later. Lung tissue obtained at autopsy from 56 patients revealed two major pathologic types: thromboembolic pulmonary hypertension in 32 patients (57%) and plexogenic pulmonary arteriopathy in 18 (32%). Thus, in more than half the patients undergoing autopsy the major histologic feature was thrombi without any evidence of plexiform lesions. The two groups were similar with respect to their clinical and hemodynamic features and short survival. Of the variables tested for prognostic importance by stepwise multivariate analysis, only two were significant: pulmonary arterial oxygen saturation (p less than .00001) and anticoagulant therapy (p = .01). Anticoagulant therapy is recommended for patients with primary pulmonary hypertension.

Mutant adenosine deaminase 2 in a polyarteritis nodosa vasculopathy

BACKGROUND

Polyarteritis nodosa is a systemic necrotizing vasculitis with a pathogenesis that is poorly understood. We identified six families with multiple cases of systemic and cutaneous polyarteritis nodosa, consistent with autosomal recessive inheritance. In most cases, onset of the disease occurred during childhood.

METHODS

We carried out exome sequencing in persons from multiply affected families of Georgian Jewish or German ancestry. We performed targeted sequencing in additional family members and in unrelated affected persons, 3 of Georgian Jewish ancestry and 14 of Turkish ancestry. Mutations were assessed by testing their effect on enzymatic activity in serum specimens from patients, analysis of protein structure, expression in mammalian cells, and biophysical analysis of purified protein.

RESULTS

In all the families, vasculitis was caused by recessive mutations in CECR1, the gene encoding adenosine deaminase 2 (ADA2). All the Georgian Jewish patients were homozygous for a mutation encoding a Gly47Arg substitution, the German patients were compound heterozygous for Arg169Gln and Pro251Leu mutations, and one Turkish patient was compound heterozygous for Gly47Val and Trp264Ser mutations. In the endogamous Georgian Jewish population, the Gly47Arg carrier frequency was 0.102, which is consistent with the high prevalence of disease. The other mutations either were found in only one family member or patient or were extremely rare. ADA2 activity was significantly reduced in serum specimens from patients. Expression in human embryonic kidney 293T cells revealed low amounts of mutant secreted protein.

CONCLUSIONS

Recessive loss-of-function mutations of ADA2, a growth factor that is the major extracellular adenosine deaminase, can cause polyarteritis nodosa vasculopathy with highly varied clinical expression. (Funded by the Shaare Zedek Medical Center and others.).

Vasculitis with hepatitis B antigenemia: long-term observation in nine patients

The development of generalized necrotizing vasculitis in association with hepatitis B antigenemia is the first example in man of a chronic rheumatic disease presumably caused by a viral infection. This report reviews the experience in nine biopsy-proven cases of hepatitis B-associated necrotizing vasculitis followed for up to six years. The natural history of the disease is emphasized and the manifestations of patients with vasculitis who carry hepatitis B antigen are compared with those of vasculitis patients who are antigen negative.

Microscopic polyangiitis with alveolar hemorrhage. A study of 29 cases and review of the literature. Groupe d'Etudes et de Recherche sur les Maladies "Orphelines" Pulmonaires (GERM"O"P)

Microscopic polyangiitis (MPA) is a systemic small-vessel vasculitis primarily associated with necrotizing glomerulonephritis and pulmonary capillaritis. In this retrospective study of 29 patients with MPA and alveolar hemorrhage (AH), we characterized the pulmonary manifestations at presentation and assessed the short- and long-term outcome. AH was diagnosed when bronchoalveolar lavage was macroscopically bloody, or contained hemosiderin-laden macrophages, in the absence of lung infection or pulmonary edema. MPA was diagnosed when AH was associated with focal segmental necrotizing glomerulonephritis at kidney biopsy or pathologically proved small-vessel vasculitis. There were 17 women and 12 men, with a mean age of 55.8 +/- 16.7 years. The onset was rapidly progressive, but in 8 (28%) patients, symptoms preceded the diagnosis for more than 1 year. The most constant systemic findings associated with AH were glomerulonephritis in 28 (97%) patients; fever (62%); myalgia and arthralgia (52%); weight loss (45%); ear, nose, and throat symptoms (31%); and skin involvement (17%). Lung opacities were bilateral in 26 (90%) patients, most frequently involving the lower part of the lungs. Bronchoalveolar lavage, performed in 27 patients, was hemorrhagic in 25 (93%), and contained numerous siderophages in others. Most patients were severely anemic (mean hemoglobin, 8.1 +/- 1.8 g/dL). ANCA, present in 27 (93%) patients, gave a perinuclear (14), cytoplasmic (11), or mixed (1) pattern. Mean serum creatinine level was 407 +/- 415 mumol/L. Renal biopsy confirmed the presence of necrotizing glomerulonephritis in 27 patients. Patients were treated with corticosteroids (100%), cyclophosphamide (79%), plasmapheresis (24%), dialysis (28%), and mechanical ventilation (10%). The overall mortality rate was 31% (9 patients). Deaths were related to vasculitis (5 patients) or side effects of treatment (4). Deaths were more frequent in aged or mechanically ventilated patients. The 5-year survival rate was 68%. The recovery of respiratory function among survivors was clinically considered complete in 20 (69%) patients. However, 7 patients (24%) had persistent alterations on pulmonary function tests. Of the 11 patients who had relapses, 2 died from AH.

Microvasculitis and ischemia in diabetic lumbosacral radiculoplexus neuropathy

OBJECTIVE

To determine whether microscopic vasculitis explains the clinical and pathologic features of diabetic lumbosacral radiculoplexus neuropathy (DLSRPN).

BACKGROUND

DLSRPN is usually attributed to metabolic derangement or ischemic injury, but microscopic vasculitis as the sole cause needs consideration.

METHODS

We prospectively studied the clinical, laboratory, and EMG features as well as the pathology of distal cutaneous nerve biopsy specimens of patients with DLSRPN.

RESULTS

Study of DLSRPN nerve biopsy specimens (n = 33) compared with those from healthy controls (n = 14) and those with diabetic polyneuropathy (n = 21) provided strong evidence for ischemic injury (axonal degeneration, multifocal fiber loss, focal perineurial necrosis and thickening, injury neuroma, neovascularization, and swollen fibers with accumulated organelles), which we attribute to microscopic vasculitis (epineurial vascular and perivascular inflammation, vessel wall necrosis, and evidence of previous bleeding). Segmental demyelination was significantly associated with multifocal fiber loss.

CONCLUSIONS

1) This severe, debilitating neuropathy begins with symptoms unilaterally and focally in the leg, thigh, or buttock and spreads to involve the other regions of the same and then opposite side and is due to multifocal involvement of lumbosacral roots, plexus, and peripheral nerve (i.e., diabetic lumbosacral radiculoplexus neuropathy). 2) Motor, sensory, and autonomic fibers are all involved. 3) Ischemic injury explains the clinical features and pathologic abnormalities of nerve. 4) The proximate cause of the ischemic injury appears to be microscopic vasculitis. 5) The segmental demyelination is probably secondary to ischemic axonal dystrophy, thus providing a unifying hypothesis for both axonal degeneration and segmental demyelination.

Primary systemic vasculitis: clinical features and mortality

BACKGROUND

Wegener's granulomatosis (WG), Churg Strauss syndrome (CSS) and microscopic polyangiitis (MPA) are primary systemic vasculitides (PSV), the clinical features of which have been described from tertiary centres.

AIM

To provide the first clinical description of MPA from a general hospital and compare clinical features with WG and CSS.

DESIGN

Retrospective analysis of patient records.

METHODS

Records of 99 PSV patients attending a single hospital, from 1988 to 2000, were reviewed for: clinical features, date/age at diagnosis, sex, duration of illness, anti-neutrophil cytoplasmic antibodies (ANCA), treatment, comorbidity and deaths. Cases were classified using ACR, CHCC and Lanham criteria/definitions. Birmingham vasculitis activity scores (BVAS) and damage index (VDI) were calculated. Survival was assessed using Cox proportional hazards model and standardized mortality ratios (SMRs).

RESULTS

Compared to previous reports there was more ENT (29%) and respiratory (29%) but less renal (92%) involvement in MPA, and less ENT involvement in WG (81%). CSS showed high neurological (72%), cardiovascular (28%) and gastrointestinal (17%) involvement and the highest median (range) VDI (p = 0.01 vs. WG; p = 0.001 vs. MPA). BVAS1 was significantly lower in MPA than in WG [median (range) 15 (4-29) vs. 21 (6-39), (p = 0.001)] but not in CSS [20 (7-28), p = 0.08]. SMR (95%CI) for PSV was 4.8 (3.0-6.6); 5-year survival was 45.1% for MPA, 75.9% for WG and 68.1% for CSS. Age was a significant risk, but only to the same extent as in the reference population. When age was adjusted for, no other significant factor was found.

DISCUSSION

The clinical characteristics seen here are similar to those in previous series. There are difficulties in using the MPA CHCC definitions in classification. There is a high proportion of neurological involvement in CSS, causing permanent damage. MPA may have a poorer prognosis than WG or CSS.

Vasculitis of the nervous system

PURPOSE OF REVIEW

Vasculitis refers to heterogeneous clinicopathologic disorders that share the histopathology of inflammation of blood vessels. When unrecognized and therefore untreated, vasculitis of the nervous system leads to pervasive injury and disability making this a disorder of paramount importance to all clinicians.

RECENT FINDINGS

Remarkable progress has been made in the pathogenesis, diagnosis, and treatment of vasculitis of the central (CNS) and peripheral nervous system (PNS). The classification of vasculitis affecting the nervous system includes (1) Systemic vasculitis disorders (necrotizing arteritis of the polyarteritis type, hypersensitivity vasculitis, systemic granulomatous vasculitis, giant cell arteritis, diverse connective tissue disorders; viral, spirochete, fungal, and retroviral infection; (2) Paraneoplastic disorders; (3) Amphetamine abuse; (4) Granulomatous angiitis of the brain; (5) Isolated peripheral nerve vasculitis, each in the absence of systemic involvement; and (6) diabetes mellitus, associated wtih inflammatory PNS vasculopathy.

SUMMARY

Vasculitis is diagnosed with assurance after intensive evaluation. Successful treatment follows ascertainment of the specific vasculitic disorder and the underlying cytochemical mechanism of pathogenesis. Clinicians must choose from among the available immunomodulating, immunosuppressive, and targeted immunotherapies, unfortunately without the benefit of prospective clinical trials, tempered by the recognition of all of the possible medication related side effects.

Polyangiitis overlap syndrome. Classification and prospective clinical experience

Ten patients were prospectively studied who had features of systemic vasculitis that could not be classified into one of the well-defined vasculitic syndromes. Since many of these syndromes had overlapping features of several distinct vasculitides, they were classified as the polyangiitis overlap syndrome. Cutaneous disease was common (nine of 10 patients) and, some patients, had been mistakenly diagnosed as "hypersensitivity" or isolated cutaneous vasculitis. The polyangiitis overlap syndrome is a systemic vasculitis, and all of the patients required therapy with cyclophosphamide (2 mg/kg per day). Nine of 10 patients were also treated with corticosteroids, which were administered initially on a daily basis followed by an alternate-day regimen. A complete remission was induced in all of the patients, with a mean follow-up duration of 58.4 months. In eight of 10 patients, remission was maintained following discontinuation of cyclophosphamide. The mean duration of remission was 45.9 months, with a mean interval after discontinuation of all therapy of 22.3 months. Two patients had relapses after the immunosuppressive therapy was discontinued; however, complete remissions were reinduced following reinstitution of therapy.

Pathology of Kawasaki disease: I. Pathology and morphogenesis of the vascular changes

Histopathological investigation of the vascular changes in Kawasaki disease was carried out on thirty-seven autopsied Japanese patients. Arterial lesions could be classified into following five stages from the view point of morphogenesis of arteritis; 1) endothelial degeneration and increased vascular permeability, 2) edema and degeneration of the media, 3) necrotizing panarteritis, 4) granulation formation, and 5) scarformation. Aneurysm with thrombus was observed mainly in the coronary artery in most patients. It is considered that the initial changes begins in the endothelial cells with increased vascular permeability. Platelet aggregation in the damaged endothelial cells seems to play an important role in the further development of the arteritic changes. Vascular lesions were observed not only in the arterial system but also in the venous system, therefore Kawasaki disease is a systemic vasculitis rather than a systemic arteritis.

Two distinct cellular patterns in cutaneous necrotizing angiitis

Two distinct cellular patterns of necrotizing angiitis involving venules in skin of patients with clinically identical cutaneous lesions were appreciated by the 1 -mum-thick section technique. In those individuals with serum hypocomplementemia, there was a perivenular inflitrate composed predominantly of neutrophils with fibrin deposition and nuclear debris. In patients with normal serum complement levels, in addition to an infiltrate of neutrophils and fibrin deposition, perivenular lymphocytes in various stages of activation were prominent. In both patterns the venules and not the arterioles were affected, mast cells exhibited various degrees of hypogranulation, and basophils and eosinophils were recognized only rarely. Lesions of different clinical age obtained from one hypocomplelmentemic patient and one normocomplementemic patient exhibited consistent cellular patterns, as did a single crop of lesions biopsied twice, 24 hr apart, in a patient with hypocomplementemia. No patient with hypocomplementemia became normocomplementemic or vice versa with persistence of lesions.

Polyarteritis nodosa, microscopic polyangiitis and Churg-Strauss syndrome

Polyarteritis nodosa (PAN), first described by Küssmaul and Maier, is a well-known form of necrotizing angiitis whose manifestations are weight loss, fever, asthenia, peripheral neuropathy, renal involvement, musculoskeletal and cutaneous manifestations, hypertension, gastrointestinal tract involvement, and cardiac failure. Recently individualized from PAN, microscopic polyangiitis (MPA) is a systemic vasculitis of small-size vessels whose clinical manifestations are very similar to those of PAN, but it is characterized by the presence of rapidly progressive glomerulonephritis (RPGN), which is nearly constant, and pulmonary involvement usually absent in PAN. Churg Strauss syndrome (CSS) is a disorder characterized by hypereosinophilia and systemic vasculitis similar to that of PAN and occurring in individuals with asthma and allergic rhinitis. Considering the etiologies of PAN, primary and secondary vasculitides can also be distinguished because PAN can be the consequence of hepatitis B virus (HBV) infection and sometimes of other etiologic agents. The prognosis of systemic vasculitides has been transformed by corticosteroids that are, except in HBV-related PAN, the basic treatment. Immunosuppressive drugs, especially cyclophophamide, have also contributed to improving the prognosis, but their precise role in the management of these vasculitides is still being elucidated.

Polyarteritis nodosa: A contemporary overview

Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis predominantly targeting medium-sized arteries. PAN is a rare form of vasculitis, and the precise frequency of this disease is difficult to determine. The major environmental factor associated with PAN is HBV infection. The pathogenesis of "idiopathic PAN" remains enigmatic, although the clinical responses to immunosuppressive therapy support the concept that immunological mechanisms play an active pathogenic role. The spectrum of disease ranges from involving a single organ to polyvisceral failure. Any organ might be affected; however, for reasons that are not understood, PAN does not affect the lungs. In addition to the systemic idiopathic form, called "idiopathic generalized PAN," there are 2 clinical variants of this disease: "cutaneous PAN" and "hepatitis B virus (HBV)-associated PAN". Diagnosis requires the integration of clinical, angiographic, and biopsy findings. The overall prognosis of this disease has been improved in recent decades, primarily reflecting early diagnosis and more effective treatments. Idiopathic generalized PAN should be treated with a combination of glucocorticoids and cyclophosphamide. The treatment of HBV-associated PAN involves a different approach, centered on the use of an antiviral agent to control the infection. The therapy for cutaneous PAN requires a less aggressive approach based on the administration of non-steroidal anti-inflammatory drugs over short periods of time.

Cutaneous polyarteritis nodosa: a clinical and histopathological study of 20 cases

Twenty cases diagnosed as cutaneous polyarteritis nodosa (CPN) and confirmed by skin biopsy over the last 17 years were reviewed in our department. Based upon their clinical features, laboratory findings, and long-term observation of the disease course, they were divided into three groups. 1) Group 1 comprised 16 cases which were classified as the mild cutaneous form. The disease was confined to the skin with occasional involvement of peripheral nerves and skeletal muscles of the affected extremity. They generally followed a benign course. 2) Group 2 comprised 2 cases classified as the severe form. Despite severe clinical manifestations and several abnormal laboratory findings, the disease was limited to the skin, muscles, and peripheral nerves without any visceral involvement over follow-up periods of 11 years and 5 years, respectively. 3) Group 3 comprised 2 cases of the progressive form; in these the disease had begun with a cutaneous lesion and progressed to the systemic form after 19 and 18 year periods of recurrent episodes of cutaneous lesions, respectively. One died of gastrointestinal bleeding. In group 3, serum antinuclear antibodies and rheumatoid factor were positive. The autoimmune mechanism seems to play a role in this group. It is clear from the results of this study that not all patients whose vasculitic lesions are apparently limited to the skin remain in a benign course. Long-term follow-up is essential.

Detection of autoantibodies against myeloid lysosomal enzymes: a useful adjunct to classification of patients with biopsy-proven necrotizing arteritis

PURPOSE

Assessment of the value of determination of antineutrophil cytoplasmic antibodies (ANCA) and its specificities for classification of patients with biopsy-proven necrotizing arteritis.

PATIENTS AND METHODS

The serum samples of 28 consecutive patients with biopsy-proven vasculitis involving medium- and/or small-sized arteries were tested for ANCA by an indirect immunofluorescence technique, by neutrophil extract enzyme-linked immunosorbent assay (ELISA), and by catching ELISA.

RESULTS

Eight patients had Churg-Strauss syndrome; six had myeloperoxidase (MPO) antibodies, and in the other two patients, ANCA were not detected. Six patients had polyarteritis nodosa (PAN) limited to the skin and the musculoskeletal system; ANCA were not detected in these patients. Two patients had systemic PAN and both had MPO antibodies. The remaining 12 patients had overlapping clinical features of the different forms of vasculitis. Five patients had polyarteritis in combination with chronic nasal inflammation and glomerulonephritis compatible with Wegener's granulomatosis (WG) but without granulomas in the respiratory tract. All five patients had 29-kd serine protease antibodies. Two patients had polyarteritis in combination with nasal polyposis and asthma compatible with Churg-Strauss syndrome, but eosinophilia was not detected. Both patients had MPO antibodies. Three patients with unclassified granulomatous arteritis had either elastase antibodies or ANCA of unknown specificity. One patient with unclassified systemic vasculitis had 29-kd serine protease antibodies, and one patient with necrotizing arteritis of the bowel in combination with Schönlein-Henoch purpura was negative for ANCA.

CONCLUSION

Determination of ANCA and its specificities is a useful adjunct to the classification of patients with biopsy-proven necrotizing arteritis. Within the spectrum of idiopathic vasculitides, 29-kd serine protease antibodies are associated with WG, MPO antibodies are associated with Churg-Strauss syndrome and systemic PAN, and PAN limited to the skin and the musculoskeletal system is not associated with ANCA.

Vasculitides in hairy cell leukemia

Forty-two cases of vasculitis coincident with hairy cell leukemia (HCL) have been reported, of which 17 had panarteritis nodosa (PAN), 21 had cutaneous leukocytoclastic vasculitis (LCV), and 4 had vessel wall infiltration by hairy cells. PAN generally occurred after the diagnosis of HCL, splenectomy, and infection. HBs antigen was detected in 3 of 12 patients tested, whereas immune complexes were positive in 3 of 4 patients tested. LCV was often preceded by infection and was frequently detected before HCL. Serum immunoglobulin levels were generally elevated when measured. Cryoglobulins, complement, rheumatoid factor, and antinuclear antibodies showed no clear association with vasculitis in HCL. These reports suggest a role for infection and splenectomy as contributing factors to vasculitis.

Vasculitis in primary vasculitides, granulomatoses, and connective tissue diseases

Problems with the classification and diagnosis of vasculitides are discussed. The evidence related to the pathogenetic importance of immune complexes in vasculitis, both in experimental models and human disease, is reviewed. The finding, by immunofluorescence, of immunoglobulins and complement components in vessel walls has provided indirect evidence of a role of immune complexes in certain forms of human vasculitis. However, specific antigens have been demonstrated in very few instances, notably in some patients with hepatitis B infection. In most forms of human vasculitis there is no information about causative factors. The widely held belief that therapeutic drugs cause an appreciable proportion of cases of human vasculitis appears unfounded.

Pathology of Kawasaki disease: II. Distribution and incidence of the vascular lesions

Histopathology, distribution and incidence of vascular changes were studied in tissues obtained at autopsy on thirty-seven children. Elastic and musculoelastic arteries showed a high incidence of arteritic changes, however the degree of the lesions was in general mild to moderate with the exception of the iliac artery, which revealed severe changes and a necrotizing panarteritis which was often accompanied with an aneurysm formation. A high incidence of arteritic changes, of which main histological feature was necrotizing panarteritis, was seen in extravisceral middle sized arteries. The coronary artery in particular was involved in each case and most had an accompanying aneurysm, some of which had ruptured. Intravisceral small sized arteries showed a relatively low incidence of arteritic changes and the degree of inflamation was in general mild. Phlebitis was present in over half the number of patients. The degree of lesions was mild in the small veins and mild to moderate in the large veins. Vascular lesions in Kawasaki disease should be termed systemic vasculitis rather than a systemic arteritis. There was a correlation between the caliber of involved vessels and the degree of vascular lesions. According to the histopathology, distribution and incidence of angitis, Kawasaki disease does resemble infantile periarteritis nodosa with the exception of the different manner of the coronary and iliac involvement.

Polyarteritis nodosa in patients with Familial Mediterranean Fever (FMF): a concomitant disease or a feature of FMF?

BACKGROUND

Familial Mediterranean Fever (FMF) is caused by mutations in the gene encoding pyrin and is characterized by self-limited, recurrent attacks of fever and serositis. Vasculitis has been increasingly reported in FMF. A study evaluating the prognosis in FMF and polyarteritis nodosa (PAN) patients has not been reported previously.

OBJECTIVES

To determine the special characteristics and the prognosis of PAN in FMF patients.

METHODS

A questionnaire was used for the present survey. The setting was 7 referral centers from Turkey and Israel. Seventeen patients who were diagnosed with FMF and who developed PAN were included. PAN was diagnosed in those who met the Chapel Hill consensus criteria for microscopic polyarteritis or classic PAN. The clinical features of these 17 patients and the outcomes of their vasculitis were analyzed.

RESULTS

The age at diagnosis of PAN in these FMF patients ranged from 3.5 to 37 years. All patients had constitutional symptoms, elevated acute phase reactants, and myalgia at the time PAN was diagnosed. The diagnosis of PAN was confirmed by renal angiography in 8 patients, by renal biopsy in 6 patients, and by muscle and/or nodule biopsies in 6 patients. A number of patients had definite features of both classic PAN and microscopic polyarteritis.

CONCLUSIONS

When compared with other PAN patients, those with FMF tended to have a younger age at PAN onset, more frequent perirenal hematomas, and an overall better prognosis. The cases with overlapping features of microscopic and classic PAN pose a problem for the current classification of vasculitis. We suggest that the clinical representation of PAN in FMF patients has certain characteristics and may be a feature of FMF per se.

Differences between anti-myeloperoxidase- and anti-proteinase 3-associated renal disease

We performed a retrospective study of the clinical features, the pattern of the pre-treatment renal function loss, the renal morphology and the outcome in 92 patients with anti-neutrophil cytoplasmic autoantibodies directed against proteinase 3 (aPR3; N = 46) or myeloperoxidase (aMPO; N = 46). Patients with aMPO had a higher median age than patients with a PR3 (63 and 56 years; P < 0.05). The mean (+/- SD) number of affected organs in the aPR3 group exceeded that of the aMPO group (3.9 +/- 1.4 and 2.2 +/- 1.1; P < 0.01). The prevalence of renal involvement did not differ between patients with aPR3 and aMPO (83% and 67%, respectively; NS). Pre-treatment renal function deteriorated significantly faster in aPR3- than in aMPO-associated renal disease. The kidney biopsies from patients with aPR3 showed a higher activity index (10.2 +/- 3.8 and 7.3 +/- 3.2; P < 0.03) and a lower chronicity index (4.5 +/- 2.6 and 7.0 +/- 3.1; P < 0.02) than biopsies from patients with aMPO. The kidney survival at two years was 73% in patients with aPR3- and 61% in patients with aMPO-associated renal disease (NS). We conclude that renal function generally deteriorates faster in aPR3- than in aMPO-associated renal disease. This goes together with more active renal lesions in patients with aPR3 and more chronic renal lesions in patients with aMPO. Despite these differences, there is no difference in outcomes between both antibody groups.