The case presented has shown a progressive, near-fatal illness with clinical, roent-genographic, and microscopic signs which support the diagnosis of Letterer-Siwe disease, the etiology of which has been postulated to be infectious.

All features of the disease process receded immediately following antibiotic therapy and no organisms could be isolated in repeated cultures following the remission. In consideration of these facts, it is believed that the case is one of Letterer-Siwe disease, in which the causative agent was isolated and healing was accomplished with antibiotic therapy.

The final proof of this interpretation will, of course, depend upon the isolation of similar or different organisms from other cases. The paracolon group are commonly discarded in the laboratory as of no significance. Thus, organisms which have been regarded as not significant or contaminants may be responsible for other cases. Only the accumulation of a considerable body of cases studied intensively will eventually prove whether or not any organisms recovered are opportunists, contaminants, or causative agents, or whether organisms can be recovered with any degree of frequency.