Background/Purpose : There is no population based epidemiologic studies of antisynthetase syndrome (ASS). We described characteristics and epidemiology of this disease in Martinique, populated by an African descent population.

Methods:   Incidence was calculated including incident cases prospectively identified from 2006 to 2013 by 3 sources in Martinique: (1) competence center for rare systemic autoimmune diseases, (2) national referral center for rare neuromuscular disorders, (3) the only respiratory medicine department, all located in the academic hospital of Fort de France. We included to describe biological and clinical characteristics, more patients from the rheumatology, internal medicine and respiratory medicine units of the 2 others French American regions (Guadeloupe and French Guiana). Inclusion criteria were: presence of one of the antisynthetase antibodies associated to muscular, rheumatologic involvement or interstitial lung disease.

Results: In the 3 regions, 41 patients (all of African descent) were found (31 from Martinique, 6 from Guadeloupe and 5 from French Guiana): 31 females, 10 males. The mean age at diagnosis was 44.1 yo (range: 25-82). Three patients were lost to follow up (none in Martinique) and 5 deceased (2.06 dead/100 patients-year). The mean follow up time was 72.3 months. Fifty one percent had anti-Jo1 antibody, 44% anti-PL12, 5% anti-PL7. Initially, the clinical picture was:  15% and 57% muscular (p< 0.05), 60 and 38% pulmonary (p>0.05), 50 and 23.8% rheumatologic (p> 0.05) for anti-PL7/PL12 and anti-Jo1 respectively. Cumulative characteristics in 41 patients showed: Interstitial lung disease 82.9% (PL7/12: 90%, Jo1: 76.2%; p> 0.05), arthritis 63.4% (PL7/12: 65%, Jo1: 62.9%; p>0.05), mechanic hands 51.2% (PL7/12: 36.8%, Jo1: 71.4%, p>0.05), fever 51.2% (PL7/12: 60%, Jo1: 42.9%; p>0.05). Clinical myopathy was found for 43.9% (PL7/12: 25%, Jo1: 61.9%; p< 0.05) and 56.1% were considered as amyopathic (34.1%; PL7/12: 45%, Jo1: 23.8%) or clinically amyopathic (22%; PL7/12: 30%, Jo1: 14.3%). Main histologic patterns at the chest CT scan were: non specific interstitial pneumonia (52.9%), usual interstitial pneumonia (23.5%), cryptogenic organizing pneumonia (5.9%), diffuse alveolar damage (3%). Myocarditis was present in 3 patients. Associated diseases were: rheumatoid arthritis (5), Juvenile idiopathic arthritis (1), systemic sclerosis (1), antiphospholipid syndrome (1), Evans syndrome (3). Pulmonary hypertension was found in 4 patients and responsible for 3 of the 5 deaths. Eighteen patients were considered as incident cases in Martinique during the 2006-2013 period, allowing a mean annual incidence of 5.3/10⁶ (PL7-12: 2.5; Jo1: 3.1). In December 31, 2013, the prevalence of ASS in Martinique was 67.5/10⁶(PL7/12: 30; Jo1: 37.5).

Conclusion: We provide the first population based epidemiology of ASS, moreover in an African origin population. We confirm the elevated proportion with anti-PL7/12 close to anti-Jo1 in our black patients from the French West Indies. This initial clinical profile, frequently mimicking infectious pneumonia with fever and high blood c reactive proteine  level without clinical myopathy, can explain difficulties in the diagnosis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/epidemiology-and-characteristics-of-antisynthetase-syndrome-in-the-african-descent-population-of-martinique/