Fukuyama Congenital Muscular Dystrophy: Clinical Aspects

Abstract

Fukuyama congenital muscular dystrophy (FCMD), the second most common muscular dystrophy in the Japanese population, is an autosomal recessive disorder caused by mutations in the fukutin (FKTN) gene. FKTN encodes a protein involved in the glycosylation of α-dystroglycan (α-DG), which is important for linking the basal lamina to cytoskeletal proteins in muscles, peripheral nerves, and the brain. The main features of FCMD are a combination of infantile-onset hypotonia, generalized muscle weakness, eye abnormalities, and central nervous system involvement with mental retardation and seizures associated with cortical migration defects. The peak motor function is seen between the ages of 2 and 8 years, and maximal motor ability is usually unassisted sitting or sliding on the buttocks. Most patients die of respiratory dysfunction, pulmonary infections including aspiration pneumonia, suffocation, or congestive heart failure. The mean life span is less than 20 years. In managing the FCMD patients, two characteristic complications should be considered. The first is frequent episodes of ketotic hypoglycemia often seen in young lean patients. The second is sudden severe exacerbation of muscle weakness following viral infections, which can be fatal. In this section, the author’s extensive experience, gained by managing nearly 200 FCMD patients, will be described.