Spontaneous pneumothorax and multiple sclerosis

Two patients with proved and one with clinically definite multiple sclerosis were found among 141 residents of Olmsted County, Minn., who were identified as incidence cases of spontaneous pneumothorax in an epidemiological study. Because the age- and sex-specific prevalence rates for multiple sclerosis had already been determined for this community, the expected prevalence of multiple sclerosis at the time spontaneous pneumothorax was diagnosed could be calculated. Even with both sexes combined, the presence of any patient with a history of multiple sclerosis in a group this small might be somewhat unusual. Three cases is an observation unlikely to have occurred by chance alone (p<0.01, based on exact confidence limits for the binomial distribution) and the authors could find no common explanation for this association.