Methylmalonic Acidemia in Mainland China

Ninety-six patients in our sample developed renal injury and 211 presented with delayed physical development and mental retardation. MRI/CT demonstrated an abnormal signal in 111 cases (31.36%). Most of our patients were treated with hydrocobalamin injections (81.64%) and carnitine via injection or oral administration at a dose of 50–100 mg/kg/day (78%). Thirty-four patients (9.6%) died, some as a result of their parents’ decision to stop treatment. Of those whom we continue to follow, 187 have done well after discharge from hospital. These families were advised to feed their children a metabolic formula and a low-protein diet, and to return to the hospital every 2 or 3 months for laboratory testing. It is unfortunate that few of these patients have had genetic analysis. Testing is not available in most parts of China and the cost of sending DNA out of the country is prohibitive. Thus, most (79.94%) of these patients were diagnosed by gas chromatography/ mass spectrometry and 20.05% were diagnosed by gas chromatography/mass spectrometry and tandem mass spectrometry. In a clinical study [4] , mutations of MUT gene were detected in 16 of 21 patients with isolated MMA. Most mutations were clustered in exons 2 and 3 (50%).