[A case of hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome with spastic paraparesis and severe distal muscle atrophy of lower limbs].

A 16-year-old boy with hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome was reported. He was the second child of first-cousin consanguineous parents. Since childhood, he was mentally retarded and had frequent episodes of vomiting but no unconsciousness attack. Because of progressive gait disturbance since the age of 15, he was admitted to Kyushu University Hospital. Neurological examination revealed mental defect and spastic paraparesis with bilateral positive pathological reflexes. Moreover, severe muscle atrophy and moderate weakness were observed in the distal portion of lower extremities. The diagnosis of HHH syndrome was made by the examination of amino acids in the serum and urine and by the incorporation study of radioactive ornithine into cultured fibroblasts. EMG and nerve biopsy studies suggested that the muscle atrophy seen in this patient was caused by the degeneration of spinal anterior horn cells. Amino acid imbalance, especially elevation of glutamine and glutamic acid in the CSF, may cause dysfunction of neuronal system including anterior horn cells.