The immunopathology of ANCA-associated vasculitis.

The small-vessel vasculitides are a group of disorders characterised by variable patterns of small blood vessel inflammation producing a markedly heterogeneous clinical phenotype. While any vessel in any organ may be involved, distinct but often overlapping sets of clinical features have allowed the description of three subtypes associated with the presence of circulating anti-neutrophil cytoplasmic antibodies (ANCA), namely granulomatosis with polyangiitis (GPA, formerly known as Wegener's Granulomatosis), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (eGPA, formerly known as Churg-Strauss syndrome). Together, these conditions are called the ANCA-associated vasculitidies (AAV). Both formal nomenclature and classification criteria for the syndromes have changed repeatedly since their description over 100 years ago and may conceivably do so again following recent reports showing distinct genetic associations of patients with detectable ANCA of distinct specificities. ANCA are not only useful in classifying the syndromes but substantial evidence implicates them in driving disease pathogenesis although the mechanism by which they develop and tolerance is broken remains controversial. Advances in our understanding of the pathogenesis of the syndromes have been accompanied by some progress in treatment, although much remains to be done to improve the chronic morbidity associated with the immunosuppression required for disease control

ANCA patients have T cells responsive to complementary PR-3 antigen

Some patients with proteinase 3 specific anti-neutrophil cytoplasmic autoantibodies (PR3-ANCA) also have antibodies that react to complementary-PR3 (cPR3), a protein encoded by the antisense RNA of the PR3 gene. To study whether patients with anti-cPR3 antibodies have cPR3-responsive memory T cells we selected conditions that allowed cultivation of memory cells but not naïve cells. About half of the patients were found to have CD4+TH1 memory cells responsive to the cPR3138-169-peptide; while only a third of the patients had HI-PR3 protein responsive T cells. A significant number of T cells from patients responded to cPR3138-169 peptide and to HI-PR3 protein by proliferation and/or secretion of IFN-γ, compared to healthy controls while there was no response to scrambled peptide. Cells responsive to cPR3138-169-peptide were not detected in MPO-ANCA patients suggesting that this response is specific. The HLADRB1* 15 allele was significantly overrepresented in our patient group and is predicted to bind cPR3138-169 peptide with high affinity. Regression analysis showed a significant likelihood that anti-cPR3 antibodies and cPR3-specific T cells coexist in individuals, consistent with an immunological history of encounter with a PR3-complementary protein. We suggest that the presence of cells reacting to potential complementary protein pairs might provide an alternative mechanism for auto-immune diseases

Myotonic dystrophy-2: Unusual phenotype due to a small CCTG-expansion

Myotonic dystrophy type 2 (MD2) is a multisystem disease, predominantly affecting the proximal limb muscles, eyes, endocrine organs, heart and intestines. Longterm asymptomatic creatine kinase (hyper-CKemia) of more than 20 years duration, in association with hyperlipidemia and diabetes, as a manifestation of MD2 has not been reported. A 52-year-old female with a history of hyper-CKemia since the age of 32 years associated with diabetes, hyperlipidemia and hyperuricemia, developed anginal chest pain and proximal muscle weakness together with clinical myotonia when opening the fists at age 51 years. Examination revealed a left anterior hemiblock, sensorimotor neuropathy, extensive myotonic discharges on needle electromyography (EMG) and a CCTG-expansion of 134 bp on the ZNF9 gene. The family history was positive for hyper-CKemia and muscle weakness. In addition, over the previous years, she had developed vesico-ureteral reflux, cutaneous melanoma, renal cysts, cervix dysplasias, thrombocytosis, cataracts, arterial hypertension, heterozygous Factor V Leiden mutation, cholecystolithiasis, multiple ovarial cysts and vitamin D deficiency. Asymptomatic, long-term hyper-CKemia in association with multisystem disease should raise the suspicion of a MD2. Rare manifestations of MD2 may be thrombocytosis, hyperuricemia, vesico-ureteral reflux, gallstones, hypertension and cyst formation. In patients with asymptomatic hyper-CKemia, needle EMG should be considered. Myotonic dystrophy type 2 may take a mild course over many years if the CCTG-expansion is short