A Monogenic Disease with a Variety of Phenotypes: Deficiency of Adenosine Deaminase 2.

OBJECTIVE: Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive autoinflammatory disorder associated with ADA2 mutations. We aimed to investigate the characteristics and ADA2 enzyme activities of patients with DADA2 compared to non-DADA2 patients. METHODS: This is a descriptive study of 24 patients with DADA2 who were admitted to the Adult and Pediatric Rheumatology, Pediatric Haematology, and Pediatric Immunology Departments of Hacettepe University. All ADA2 exons were screened by Sanger sequencing. Serum ADA2 enzyme activity was measured by modified spectrophotometric method. RESULTS: Twenty-four patients with DADA2 were included: 14 with polyarteritis nodosa (PAN)-like phenotype (Group 1); 9 with Diamond-Blackfan anemia (DBA)-like features, and 1 with immunodeficiency (Group 2). Fourteen PAN-like DADA2 patients did not have the typical thrombocytosis seen in classic PAN. Inflammatory attacks were evident only in Group 1 patients. Serum ADA2 activity was low in all patients with DADA2 except one, who was tested after hematopoietic stem cell transplantation. There was no significant difference in ADA2 activities between PAN-like and DBA-like patients. In DADA2 patients with one ADA2 mutation, serum ADA2 activities were as low as those of patients with homozygote DADA2. ADA2 activities were normal in non-DADA2 patients. ADA2 mutations were affecting the dimerization domain in Group 1 patients and the catalytic domain in Group 2 patients. CONCLUSION: We suggest assessing ADA2 activity along with genetic analysis because there are patients with one ADA2 mutation and absent enzyme activity. Our data suggest a possible genotype-phenotype correlation in which dimerization domain mutations are associated with PAN-like phenotype, and catalytic domain mutations are associated with hematological manifestations.

ADA2 deficiency (DADA2) as an unrecognised cause of early onset polyarteritis nodosa and stroke: a multicentre national study.

OBJECTIVES: To analyse the prevalence of CECR1 mutations in patients diagnosed with early onset livedo reticularis and/or haemorrhagic/ischaemic strokes in the context of inflammation or polyarteritis nodosa (PAN). Forty-eight patients from 43 families were included in the study. METHODS: Direct sequencing of CECR1 was performed by Sanger analysis. Adenosine deaminase 2 (ADA2) enzymatic activity was analysed in monocyte isolated from patients and healthy controls incubated with adenosine and with or without an ADA1 inhibitor. RESULTS: Biallelic homozygous or compound heterozygous CECR1 mutations were detected in 15/48 patients. A heterozygous disease-associated mutation (p.G47V) was observed in two affected brothers. The mean age of onset of the genetically positive patients was 24 months (6 months to 7 years). Ten patients displayed one or more cerebral strokes during their disease course. Low immunoglobulin levels were detected in six patients. Thalidomide and anti-TNF (tumour necrosis factor) blockers were the most effective drugs. Patients without CECR1 mutations had a later age at disease onset, a lower prevalence of neurological and skin manifestations; one of these patients displayed all the clinical features of adenosine deaminase 2deficiency (DADA2) and a defective enzymatic activity suggesting the presence of a missed mutation or a synthesis defect. CONCLUSIONS: DADA2 accounts for paediatric patients diagnosed with PAN-like disease and strokes and might explain an unrecognised condition in patients followed by adult rheumatologist. Timely diagnosis and treatment with anti-TNF agents are crucial for the prevention of severe complications of the disease. Functional assay to measure ADA2 activity should complement genetic testing in patients with non-confirming genotypes.

Co-existence of renovascular hypertension, polyarteritis nodosa, antiphospholipid syndrome and methylenetetrahydrofolate reductase mutation.

We present a hypertensive child with a co-existence of polyarteritis nodosa, anti-phospholipid antibodies (aPL), methylenetetrahydrofolate reductase (MTHFR) mutation and increased lipoprotein a level. Elevated renin, aldosterone and aPL levels, micro-aneurysms, occlusion and thrombosis at left and right renal artery were found. Anti-hypertensive agents, prednisolone and pulse cyclophosphamide therapy were started and a stent was inserted in the left renal artery. Two months later, brain magnetic resonance imaging/magnetic resonance imaging angiography showed acute infarct area of the left parietofrontal lobe and middle cerebral artery stenosis. We found bilateral peripheral neuropathy, persistent aPL and elevated Lp(a) level and heterozygous A1298C/MTHFR mutation. Intravenous immunoglobulin and low-molecular-weight heparin treatment was added. In conclusion, our observation suggests that in patients with systemic vasculitis, such as polyarteritis nodosa, aPL are probably associated with greater thrombotic risks. The investigation of the LP(a) levels and MTHFR mutations as a synergic pro-coagulant effect might also be considered for determining patients with vasculitis at risk for severe thrombotic events.

Anti-carbonic anhydrase III autoantibodies in vasculitis syndrome.

AIM: To identify autoantibodies useful in the diagnosis of primary vasculitides. METHODS: The presence of antibodies against proteins in the lysate of mouse blood vessels was examined by two-dimensional electrophoresis followed by Western blotting for the pooled serum sample from patients with various forms of vasculitis: polyarteritis nodosa (PAN), microscopic polyangiitis (MPA), Wegener's granulomatosis (WG) and Takayasu's arteritis (TA). Autoantigenicity in patients with vasculitides was examined by Western blotting and enzyme-linked immunosorbent assay (ELISA). Clinicopathological correlations between the positivity of the autoantibodies and clinical status of patients with the vasculitis were examined. RESULTS: The autoantigen detected in the lysate of pooled sera from patients with vasculitides was identified by mass spectrometry as carbonic anhydrase III (CAIII). ELISA showed significantly higher prevalence of anti-CAIII antibodies in MPA patients (MPA, 11/23 [47.8%]; healthy controls, 2/32 [6.3%]; P < 0.001). Further, anti-CAIII antibody-positive MPA patients had higher vasculitis activity scores compared to anti-CAIII antibody-negative patients, and a weak and not significant negative correlation was observed between anti-CAIII antibody levels and myeloperoxidase - anti-nuclear cytoplasmic antibody (MPO-ANCA) levels. No significant differences were found in anti-CAIII autoantibody levels between MPA and the other primary vasculitides. CONCLUSION: We found significantly high prevalence of anti-CAIII antibody levels in sera from MPA patients. Although the number of samples available in this study is small and anti-CAIII autoantibodies display weak specificity for MPA, anti-CAIII antibodies may be useful for diagnosing MPA in patients who have no ANCA, as well as for assessing disease activity.

The renin-angiotensin system as a primary cause of polyarteritis nodosa in rats.

Polyarteritis nodosa is a necrotizing vasculitis of medium-sized arteries of unknown origin. Hypertension is present in 30% of patients with polyarteritis nodosa. In those cases, high renin levels are thought to be secondary to renal involvement. The present study was performed to identify causal factors of polyarteritis nodosa. In cyp1a1ren-2 transgenic rats, vasculitis of medium-sized arteries resembling classical polyarteritis nodosa can be induced. In this model, oral administration of indole-3-carbinol (I3C) activates the liver-specific cyp1a1 promoter, leading to prorenin expression in a dose-dependent manner. After the first 6 weeks of chronic induction with 0.125% I3C, the mean arterial pressure reached a plateau of about 170 mmHg. Ten out of 11 I3C-treated rats, which were chronically instrumented with a telemetric device to measure blood pressure, developed polyarteritis nodosa within 10 weeks of I3C treatment. I3C alone or instrumentation alone did not cause polyarteritis nodosa. The angiotensin-converting enzyme inhibitor captopril completely prevented the development of polyarteritis nodosa, indicating that local angiotensin II generation is a pathogenetic factor in this model. The renin-angiotensin system can play a primary role in the development of polyarteritis nodosa in rats.

Muscle involvement in polyarteritis nodosa: report of a patient presenting clinically as polymyositis and review of the literature.

Muscle symptoms, especially myalgias, appear to be common in patients with polyarteritis nodosa (PAN). We describe a patient who presented with a generalized myopathy and elevated creatine kinase (CK) suggestive of polymyositis. However, subsequent exploratory surgery for an acute abdomen revealed colonic perforation on the basis of PAN. A review of the literature suggests that generalized myopathy and elevated CK are uncommon features of PAN. A muscle biopsy can be a helpful procedure to secure the diagnosis in patients with PAN especially those with myopathies. Strategies for optimizing the choice of biopsy site are discussed.

Elevations of neutrophil proteinase 3 in serum of patients with Wegener's granulomatosis and polyarteritis nodosa.

OBJECTIVE: To determine serum levels of proteinase 3 (PR3) in normal subjects and patients with Wegener's granulomatosis (WG), polyarteritis nodosa (PAN), chronic renal failure, and systemic lupus erythematosus (SLE). METHODS: Serum levels of PR3 were measured by enzyme-linked immunosorbent assay employing a monospecific rabbit polyclonal antibody against PR3. RESULTS: Quantifiable levels of PR3 were detected in all serum samples examined, including those of normal subjects. Marked elevations of serum PR3, which decreased with treatment, were found in patients with active WG. Patients with PAN, SLE, and chronic renal failure also showed elevated levels of PR3. CONCLUSION: Quantitating serum PR3 may be useful in the management of patients with WG and other connective tissue diseases.

Human neutrophil elastase: degradation of basement membrane components and immunolocalization in the tissue.

Human neutrophil elastase was purified to homogeneity as two isozymes named E1 and E2. The isozymes degraded Type IV collagen, laminin, fibronectin, and heparan sulfate proteoglycan similarly to each other. The degradation of such basement membrane components by elastase may assist the extravasation of neutrophils in the process of inflammation. Among the substrates tested, only type V collagen, which is susceptible to neutrophil gelatinase, was resistant to elastase. This broad substrate specificity of the enzyme may also contribute to tissue destruction at the sites of inflammation. We produced a monoclonal antibody against the purified enzyme and applied it to immunohistochemical studies. In bronchopneumonia and polyarteritis nodosa, elastase was associated with the cleaved elastic fibers, indicating that the enzyme really destroys tissue in vivo. In the exudates of rheumatoid joint, elastase was stained as diffuse fine granules. Immunohistochemical studies with the monoclonal antibody will provide a complementary way to disclose the mechanism of diseases related to neutrophil infiltration.

Cutaneous periarteritis nodosa. Hepatitis B surface antigen-containing immunocomplexes and polymorphonuclear-leukocyte lysosomal enzyme release.

In a patient with cold-induced cutaneous periarteritis nodosa, cryoprecipitation of a circulating hepatitis B surface antigen-containing immunocomplex resulted in phagocytosis by neutrophils and monocytes with prominent vacuolation of the cells and extracellular release of lysosomal enzymes. We believe this immunocomplex attached itself to the cell membrane and induced vacuolation and degranulation in normal neutrophils.