Affiliations: Department of Genetics, Pediatric Institute, Kuala
Lumpur Hospital, Kuala Lumpur, Malaysia | Department of Pediatrics, Hospital Sultanah Aminah, Johor, Malaysia | Molecular Diagnostics and Protein Unit, Institute for
Medical Research, Kuala Lumpur, Malaysia
Note: [] Correspondence: Dr. Shanti Balasubramaniam, Department of
Genetics, Pediatric Institute, Kuala Lumpur Hospital, 50586 Jalan Pahang, Kuala
Lumpur, Malaysia. Tel.: +60 1633 74039; Fax: +60 6764 7092; E-mail: [email protected]
Abstract: Isolated sulfite oxidase deficiency is a rare but devastating
autosomal recessive neurometabolic disorder characterized by neonatal-onset
encephalopathy mimicking hypoxic-ischemic insult with intractable seizures and
profound neurological dysfunction. Infants who survive characteristically
manifest severe psychomotor retardation, progressive microcephaly, spastic
quadriparesis, opisthotonus, movement disorders and lens dislocation. Sulfite
oxidase is a mitochondrial enzyme encoded by the SUOX gene and is
essential for the detoxification of sulfite, the terminal reaction in the
degradation of sulfur-containing amino acids. Laboratory evidence of the
disease includes a positive urinary sulfite dipstick test, abnormal amino acid
profile with elevated plasma or urinary S-sulfocysteine level, high taurine and
reduced cysteine concentration in plasma whilst serum uric acid and urinary
excretion of uric acid, xanthine and hypoxanthine are normal. Brain magnetic
resonance imaging demonstrates a pattern reminiscent of that observed in
hypoxic-ischemic encephalopathy characterized by temporal alterations of
initial cerebral edema and later severe white matter cavitary changes
representing cystic encephalomalacia. In the absence of perinatal asphyxia,
isolated sulfite oxidase deficiency should prompt appropriate biochemical
evaluation. This report describes a male infant who presented with neonatal
seizures and neuroimaging findings suggestive of ischemic encephalopathy.
