INFANTILE FIBER-TYPE DISPROPORTION, MYOFIBRILLAR LYSIS AND CARDIOMYOPATHY - A DISORDER IN 3 UNRELATED DUTCH FAMILIES

An apparently new cardioskeletal myopathy is reported in three unrelat ed families. Five infants were affected by rapidly progressive general ized muscle weakness, with onset shortly after birth, and dilated card iomyopathy. All had generalized tremor (clonus) starting in the first week of life. The disease was lethal in all cases between 4 and 6 mont hs. Muscle biopsy, performed in four of the five patients, showed a li ght microscopic pattern of small type I and normal-sized type II fibre s. By electron microscopy small fibres were affected by myofibrillar d isruption and swelling of organelles. Findings in blood and urine sugg ested a disturbance in energy metabolism but an extensive search for r espiratory chain disorders and disorders of mitochondrial fatty acid o xidation in frozen muscle and cultured fibroblasts was negative. The f indings support a new progressive autosomal recessive infantile cardio skeletal myopathy in which type I muscle fibres are preferentially aff ected. (C) 1998 Elsevier Science B.V. All rights reserved