[Sulfite oxidase deficiency presenting as Leigh syndrome].

Background: An enzyme deficiency can be demonstrated in 15 to 20% of cases of Leigh syndrome. A case of isolated sulphite oxidase deficiency is reported in a girl presenting with Leigh syndrome.
Case Report: An 8 month-old girl was admitted suffering from hypotonia and slow increase of head circumference (-1 SD). Examination showed spastic quadriplegia, dyskinesia, axial hypotonia and difficulties in swallowing. The patient had a coarse face, broad nasal bridge, long philtrum and ectopia lentis. Brain CT scan showed bilateral hypodensity of lenticular nuclei and moderate cortical atrophy. Amino acid chromatography showed accumulation of S sulfocysteine and low levels of cysteine. The sulphite test was positive. Sulphite oxidase activity in fibroblasts and liver was undetectable contrasting with a normal activity of xanthine oxidase. Progressive brain damage led to death at 1 year of age. Prenatal diagnosis of sulphite oxidase deficiency was made in two further pregnancies.
Conclusions: The search for sulphite oxidase deficiency must be included in discussing the etiology of Leigh syndrome; the sulphite test is a simple method of screening such cases.