A study of scleroderma in South Australia: prevalence, subset characteristics and nailfold capillaroscopy

Background: Scleroderma is a systemic rheumatic disorder seen in a wide range of clinical specialties. Aims: To establish the prevalence and mortality rates of scleroderma in South Australia (SA), to determine the relative frequency and characteristics of the three principal subsets (diffuse, limited and overlap), and to examine the role of nailfold capillaroscopy in subset identification and implied prognosis. Methods: Outpatient and discharge diagnostic indexes from five major teaching hospitals in SA were reviewed between February 1987 and November 1993. A total of 215 patients with scleroderma were identified. Case notes of 115 of these patients were reviewed in order to validate scleroderma diagnosis, and subset characteristics such as sex, mean age at diagnosis, extent of skin involvement, internal organ involvement and serology were analysed. Fifty‐two of these patients were then examined prospectively to confirm positive discharge diagnosis, and nailfold capillaroscopy was performed on these patients. Results: The point prevalence of scleroderma in SA for 1993 was estimated to be 208/10⁶. This figure is a conservative estimate and is higher than most other reported series. The female to male ratio was 4:1. The majority of patients had limited disease with a ratio of 6:1:1.6 limited vs diffuse vs overlap. Systemic involvement excluding the oesophageal component in limited disease was found predominantly in the diffuse group. Autoimmune serology was positive in 90% of patients, with Scl‐70 being more common in diffuse scleroderma, anti‐centromere antibody (ACA) in the limited form and anti‐ribonucleoprotein (RNP) in the overlap form. Nailfold capillaroscopy was useful in predicting disease‐subtype as capillary dilatation was observed predominantly in limited disease, and capillary dropout in diffuse disease. Conclusions: Scleroderma is more common in SA than previously recognised. Limited disease is more common than diffuse or overlap disease, carries a better prognosis and is associated with ACA. Nailfold capillaroscopy is a useful tool in disease assessment and may provide useful diagnostic and prognostic information.