Electron microscopic study of fingernails in the disease of Mljet (Mal de Meleda)

Results are presented of the electron-microscopic examinations of fingernail clippings from 4 patients suffering from Mljet (Mal de Meleda) disease, of 3 obligate heterozygotes of this autosomal recessively inherited disease, as well as of 3 controls. In the nails of the diseased persons, significantly more osmiophilic material was found than in those of controls. In the nails of heterozygotes, the findings were intermediate between those of patients and controls. In the nails of aged persons, a strongly osmiophilic matrix keratin was found. Histochemically, lipids were demonstrated in the ventral plate of diseased nails. The probable significance and implications of these findings are discussed.