Association of Krabbe leukodystrophy and congenital fiber type disproportion.

Hypotonia and weakness developed in a 12-month-old boy whose psychomotor development had previously been normal. The muscle biopsy demonstrated a disparity in the mean diameters of type 1 and type 2 fibers and satisfied major histologic criteria for diagnosis of congenital fiber type disproportion (CFTD). However, deterioration of motor and mental function, which developed subsequently, strongly suggested progressive encephalopathy. Examination of leukocyte cerebral enzymes at 15 months of age revealed a complete lack of galactosylceramide-beta-galactosidase. Selective type 1 fiber atrophy with type 1 fiber predominance has been observed in various conditions, including Krabbe disease. We report an additional case of Krabbe leukodystrophy associated with CFTD. The finding on the molecular level will resolve the dilemma of whether CFTD is a congenital myopathy or whether these patterns of disproportion may result from a number of different processes that interfere with the maturation of the developing motor unit.