FSHD / OPMD / EDMD / DMI: P.368Clinical characteristics of 4 patients with childhood-onset reducing body myopathy in Japan

Abstract

FHL1 mutations are associated with reducing body myopathy; however, the number of case reports with childhood onset is limited. To investigate the clinical characteristics of patients who had reducing bodies in muscle biopsy and FHL1 gene mutations. Of the 939 patients who underwent biopsy at the age of 15 years or younger since 2000, 4 who had reducing body myopathy were selected. Age at onset, sex, clinical symptoms, CK level, muscle imaging findings, histological findings, and gene mutations were examined. Two cases had early childhood onset, and the remaining had late childhood onset. The cases of early childhood onset were diagnosed as myositis due to rapid progression of muscle weakness. CK level was 287-1050IU/L. Muscle biopsy showed mild to marked necrotic and regenerating fibers with reducing bodies. Case 1; 1-year 4-month-old boy developed cervical instability and progressive proximal muscle weakness. He had difficulty in standing at the age of 1 year 7 months. Muscle MRI revealed diffuse STIR high intensity in lower extremity. Case 2; 1-year 6-month-old girl developed a gait disturbance. She had difficulty in standing at 2 years. She developed respiratory failure and required NPPV and died from asphyxia at 3 years. Case 3; 10-year-old boy developed a gait disturbance. He was diagnosed as limb-girdle muscular dystrophy. Muscle CT revealed fatty replacement in the neck, trunk, and thigh. He became wheelchair user at 13 years and required NPPV from 19 years. Case 4; 13-year-old boy became slow in running. He had rigidity in the neck and trunk. He was diagnosed as ankylosing spondylitis. Muscle CT revealed findings similar to those in case 3. He became wheelchair user at 19 years and required NPPV from 30 years. We should consider the MAG staining in the muscle biopsy for the accurate diagnosis and treatment of reducing body myopathy.