Infantile isolated sulphite oxidase deficiency: Report of a case with negative sulphite test and normal sulphate excretion

Abstract

We present the clinical and biochemical data of a patient with infantile isolated sulphite oxidase deficiency with late onset of symptoms. A comparison of the biochemical parameters is made with the neonatal type of this disease and with the data of described patients with the combined defect of sulphite oxidase and xanthine oxidase, due to molybdenum cofactor deficiency. False-negative sulphite dip stick test as a pitfall in the diagnosis of sulphite oxidase deficiency is discussed.

Spherophakia associated with molybdenum cofactor deficiency

“…There are various possible reasons. First, the sulfite test gives reliable results only if performed on fresh urine; moreover, a negative sulfite test was reported in 1 patient [van der Klei-van Moorsel et al, 1991]. Second, uric acid in serum and urine is virtually undetectable in some patients, but measurable, albeit low, in others, like our patient.…”

Isolated sulphite oxidase deficiency mimics the features of hypoxic ischaemic encephalopathy

“…Dipstick analysis for urinary sulphite is unreliable owing to rapid oxidation of sulphite to sulphate at room temperature [15], and falsepositive results have also been reported [4]. Urinary thiosulphate measurement may be associated with both false-positives [8] and false-negatives [2].…”

Molybdopterin synthase mutations in a mild case of molybdenum cofactor deficiency

“…The clinical symptoms are indistinguishable from those of molybdenum cofactor de®ciency with the notable exception that xanthinuria is absent. Milder cases of isolated sul®te oxidase de®ciency have also been described [van der Klei-van Moorsel et al, 1991;Barbot et al, 1995] and, in fact, are somewhat more prevalent than the less severe forms of molybdenum cofactor de®ciency.…”