Pyridoxine-Responsive Homocystinuria with Ruptured Sinus of Valsalva in a Chinese Boy

Abstract

Homocystinuria (McKusick 236200) is an inborn error of amino acid metabolism. The frequency of the condition has been estimated at one in 2000000 population in Taiwan by newborn screening. We report one such case who had congenital aneurysm of aortic sinus and sudden rupture of sinus of Valsalva. The patient is a 14-year-old Chinese male who had presented with marfanoid habitus, pectus excavatum and mental retardation but no lens subluxation. He came to visit us owing to acute onset of chest pain, dyspnoea and development of a loud to-and-fro murmur with thrill and heave . Echocardiography showed ruptured aortic sinus of Valsalva and prolapse of right coronary cusp into right ventricle (RV) with systolic (mainly) and diastolic flow from aorta into RV (pressure gradient 117 mmHg), as well as ventricular septal defect (VSD, 2.0 cm in diameter) and dilation of both ventricles and aorta. Resection of the ruptured aneurysm of the aortic sinus of Valsalva, repair of VSD and aortic valvuloplasty and aortoplasty were done smoothly. Histological examination revealed myxoid degeneration with mild mononuclear cell infiltration. There was no evidence of infective endocarditis. Chromosome study, including fragile X, was normal. Urine tests with both silver-nitroprusside and cyanide- nitroprusside were positive . Plasma methioine was 5.2μmol/L (normal 3.4- 27.8), homocystine 35μmol/L (normal 0.3-5.8) detected following immediate precipitation of protein after blood-sampling ( Gaull et al 1974). After 2 weeks' intake of pyridoxine (100 mg/day) the homocystine disappeared and both urine tests became negative. Aneurysm of the aortic sinus as a complication of Marfan syrfan syndrome or secondary to infective endocarditis has been reported (Arey 1984), but not in homocystinuria.