Scleroderma and survival.

Scleroderma (systemic sclerosis) is a multisystem disorder which can often be confined to the connective tissues outside the major organ systems. The morbidity, and ultimately the mortality, risk from scleroderma stems, however, from the possible involvement of the lungs, heart, or kidneys. The disease itself is rare and often fatal when one of a number of different combinations of internal organs is affected. As a consequence, overall survival rate is a useful measure of outcome, which can be applied across groups of patients in studies of natural history. This is different from the situation with other connective tissue disorders, such as systemic lupus erythematosus, which have a relatively low mortality' and for which other outcome indicators are more appropriate.2 3 The other advantages of adopting survival as the standard measure of outcome are the relative ease of obtaining mortality data and the standardisation in data collection between centres. There are a number of problems in interpreting survival data from the various centres. Firstly, as mentioned above, scleroderma is a rare disease with an annual incidence of under 10 per million population in both the United Kingdom4 and other countries.5 Inevitably, therefore, expertise at managing patients with scleroderma becomes concentrated in a few tertiary referral centres, and it is from such centres that the natural history data emerge. Such centres, however, are likely to receive the more severe cases and thus their experience might overestimate the true mortality from scleroderma. Secondly, there is often a long delay between clinical onset and referral due to Rheumatism Coa cil the nature of the early features,6 and calculating Epidemiology Research survival from first attendance ignores that Unit, Manchester referral gap. Thirdly, retrospective studies of University Medical survival in patient attenders using their recalled