Two Cases of HHH Syndrome in Siblings

ABSTRACT

Hyperornithinemia-hyperammonemia-homocitrullinuria(HHH) syndrome is a rare autosomal recessive disorder caused by a defect in the urea cycle. Protein intolerance, mental retardation, seizure, ataxia, and stupor are characteristic symptoms. Patients showing these symptoms may also present symptoms of acute hepatic disease at the same time. When fed with a high protein diet, they may refuse to eat, vomit, become lethargic, or go into coma. After childhood, most patients avoid meats or milk spontaneously and eat a low protein diet. The liver and spleen are normal or slightly enlarged. The coagulation time is prolonged and sometimes there is a deficiency in factor VII and X. Treatment is aimed at preventing hyperammonemia after meals by restricting daily protein intake to 1.2 g/kg/day and this lowers serum ornithine concentration. Prolonged ornithine supplement(0.5 to 1.0 mM/kg/day; i.e., 66 to 132 mg/kg/day divided into three doses) improved patients' protein intolerance and accelerated growth. Since Shih and coworkers first reported this syndrome in 1969, there have been 40 cases reported worldwide but not yet in Korea. We, for the first time in Korea, report two cases of HHH syndrome in brothers.