Scleromyositis (scleroderma/polimyositis overlap) is an entity

Török L, Dankó K, Cserni G, Szûcs G. PM-SCL autoantibody positive scleroderma with polymyositis (mechanic's hand: clinical aid in the diagnosis). JEADV 2004; 18: 356–359 Török et al.1 describe a typical case of scleroderma-dermatomyositis overlap, stressing characteristic clinical, immunological and immunogenetic associations, relatively benign course in spite of the presence of lung fibrosis and response to small doses of corticosteroids. Therefore the recognition of this syndrome and its differentiation both from scleroderma (SSc) and dermatomyositis (DM) is practically important. The authors describe hyperkeratotic chronic eczema of the hands (so called mechanic's hand) as a highly characteristic symptom of the disease, of diagnostic significance. This overlap has features both of SSc and DM, variously pronounced in individual cases. The most characteristic symptoms mimicking SSc are: Raynaud's phenomenon, myalgia or arthralgia, indurated oedema of the hands and/or puffy fingers, usually slight sclerodermiform mask-like facies, dysphagia (or oesophagus dysmotility), and in about 30% of patients interstitial lung disease (ILD), not infrequently detected only by functional tests.2,3 The overlapping features of dermatomyositis [periorbital oedema and erythema, Gottron papules and sign, myalgia and/or atrophies of muscles, erythematous and poikilodermatous lesions on the trunk and arms (‘shawl sign’)] were found variously pronounced in the course of the disease. Torok et al. stress the importance of ‘mechanic's hands’ for diagnosis of this syndrome. The chronic hyperkeratotic eczematous changes of the hands may be present in all types of inflammatory myopathies, i.e. synthetase syndrome and dermatomyositis.4 Their occurrence in the patients with scleromyositis would speak in favour of its relationship with the group of autoimmune myositis, however this symptom does not appear to be specific and of diagnostic significance for this overlap. In our series of scleromyositis it was very rare. In general, the muscle involvement in scleromyositis is rather mild, with slight or no abnormalities of muscle enzymes in a proportion of patients and with slight myogenic involvement in electromyography.5–7 We observed arthralgia or arthritis almost with the same frequency as myalgia, and we have seen several cases in which deformities of fingers and hands persisted after all symptoms of the disease regressed. Skin changes in scleromyositis of SSc or DM type are variable, at one time the clinical presentation may be more characteristic of SSc, and at another time, of DM. Due to this variability patients seen by different physicians at different times are diagnosed as having SSc, DM or scleroderma/polymyositis overlap. This overlap syndrome has usually a rather benign protracted course in spite of presence of interstitial lung disease in 30–40% of adult patients. Most importantly, the small or moderate doses of corticosteroids are usually sufficient to control the disease, whereas an aggressive therapy as in SSc and DM could be more harmful than the disease itself, and is not required. Since scleromyositis has such a changeable clinical presentation, the view concerning this entity could be based only on a large series followed-up for several years. Our study consisted of 58 adults and 32 children followed-up for 1–12 years (mean 7.7 years).7 Marguerie et al.8 in the study of 32 patients followed-up for 8 years, showed similar clinical characteristics of this overlap syndrome, but a higher frequency of ILD (up to 80% of patients) and calcinosis (up to 46%). This might be due to the different patient population since patients with more prevalent skin involvement are often referred to dermatologists, and not seen by rheumatologists. Scleromyositis, in contrast to SSc, is rather frequent in children (37% of our cases), having some peculiarities in childhood: less frequent visceral involvement than in adults, no ILD (although slight functional abnormalities were found in about 20% of children), less frequent Raynaud's phenomenon (11.7% vs. 27% in adults), more frequent calcinosis (18.1% vs. 9.8%).5,7 We have not observed in children severe vascular changes, non-infrequent in childhood dermatomyositis. The PM/Scl antibody9,10 shows a very strong association with scleromyositis. This antibody, best studied by immunofluorescence (homogenous nucleolar staining, negative mitoses) and double immodiffusion, is not disease specific since in a small proportion of cases it may be associated with other CTD or CTD/overlap (in our series in about 17%), however, it is highly characteristic of this syndrome, and was present in all patients recognized as scleromyositis.2,6 Torok et al. share the view that the relevance of PM/Scl antibody is similar to that of UIRNP in MCTD, which are not specific of the overlap but all cases of MCTD are associated with high titres of this antibody.11,12 However it is rather difficult to agree with Torok et al. that the relevance of PM/Scl in scleromyositis is similar to that of anti-Scl-70 antibody in SSc, anti-Mi-2 in DM, or anti-Sm in SLE since these antibodies are specific for defined subsets. Thus, immunological marker PM/Scl is highly characteristic, although not specific for scleromyositis. Nevertheless, clinical-serological correlations are of diagnostic importance, and all our cases recognized as scleromyositis had this antibody. The immunogenetic marker of scleromyositis was found DR3.13 Using molecular typing technique,14 we found HLA-DRBIx 0301 in about 94% and HLA-DQAIx 0501 in 100% of patients with scleromyositis studied.3 These alleles in significantly increased frequency are associated with the autoimmune haplotype,15 and were also detected in the patient of Torok et al. Interestingly, in their case DRBIx 02 alleles were also found, believed to be protective against the development of idiopathic inflammatory myopathies, at least in Polish population.16 These alleles could be the cause of a relatively mild course of the disease. Altogether, based on clinical, immunological and immunogenetic findings in a large series of patients, followed-up for a long period, we believe that scleromyositis should be recognized as an entity within CTD overlap syndromes.