A Thai Boy with Hereditary Enzymopenic Methemo- globinemia Type II

VORASUK SHOTELERSUK, M.D.*, PIYARATANA TOSUKHOWONG, M.Sc. **, PAIR OJ CHOTIVITA Y ATARAKORN, M.D.***, WIROJE PONGPUNLERT, M.D.****

Affiliation : * Unit of Endocrinology, Genetics and Metabolism, Department of Pediatrics, ** Department of Biochemistry, *** Unit of Cardiology, Department of Pediatrics, **** Unit of Neurology, Department of Pediatrics, Faculty of Medicine, Chulalongkom University, Bangkok 10330, Thailand.

AbstractIndividuals with methemoglobin exceeding 1.5 g/dl have clinically obvious central cyanosis. Hereditary methemoglobinemia is due either to autosomal dominant M hemoglobins or to autosomal recessive enzymopenic methemoglobinemia. Four types of enzymopenic methemoglobinemia have been described. In addition to methemoglobinemia, individuals with type II, which is the generalized cytochrome b5 reductase deficiency, have severe and progressive neurological disabilities.
Here we report a 3-year-old Thai boy with type II hereditary enzymopenic methemo- globinemia. He was born to a second-cousin couple. His central cyanosis was first observed around 10 months of age. His neurological abnormalities were seizures beginning at 1 year of age, micro- cephaly, and inability to hold his head up. His cardiovascular and pulmonary evaluations were unremarkable. Methemoglobin level by spectral absorption pattern was 18 per cent. A qualitative enzymatic assay confirmed the deficiency of the cytochrome b5 reductase enzyme. With this definite diagnosis, a prenatal diagnosis for the next child of this couple will be possible.

Keywords : Methemoglobinemia, Cytochrome b5 Reductase

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