ABSTRACT
Objective:To study the clinical and laboratory characteristics of neonatal isolated sulfite oxidase deficiency (ISOD).Methods:An infant with neonatal ISOD admitted to our hospital was retrospectively analyzed. Using key words "isolated sulfite oxidase deficiency", "SUOX gene", "Infant, newborn", databases including CNKI, Wanfang database, National library and literature center of science and technology, China science paper online, PubMed, Web of Science and EMBASE (up to January 2021) were searched and literature review was conducted. The clinical manifestations, laboratory results, treatment and prognosis were analyzed.Results:Our patient was a full-term male infant with eye movement disorder, refractory seizures, feeding difficulties, increased muscle tone, developmental retardation and microcephaly. Urine sulfite paper-strip test was positive. Uric acid was normal. Whole exon sequencing (WES) revealed SUOX c.475G>T and c.1201A>G compound heterozygous mutations. Cranial MRI showed multiple encephalomalacia and brain atrophy at 5-month of age. The infant died at 8-month. In the literature review, a total of 29 articles and 32 cases of neonatal ISOD were found. 87.5% of the cases developed symptoms within 1-week after birth. All had convulsive seizures. Some of them had feeding difficulties, muscle tone changes, developmental retardation, microcephaly and ectopia lentis. Cranial imaging showed white matter cystic lesions and brain atrophy. Laboratory examination showed elevated urinary sulfite and S-sulfocysteine. Uric acid and xanthine/hypoxanthine were normal. Blood homocysteine was decreased. 23 cases received genetic testing and all of them had SUOX mutations. The treatment was mainly symptomatic relief and supportive treatment. During follow-up, 15 cases died, 13 cases survived and 4 cases were unknown. All the surviving children had drug-resistant convulsions and developmental retardation.Conclusions:Neonatal ISOD may present with refractory convulsions, feeding difficulties and developmental retardation. Cystic white matter changes and brain atrophy may be seen on cranial imaging. Elevated urinary sulfites, decreased blood homocysteine and normal uric acid are important clues for diagnosis. Genetic testing is helpful for early diagnosis.
ABSTRACT
The clinical data of a case with late-onset isolated sulfite oxidase deficiency(ISOD)admitted in the Department of Neurology, Children′s Hospital, Zhejiang University School of Medicine in July 2021 were retrospectively analyzed.Fifteen previously published cases of late-onset ISOD were also reviewed.The patient was a girl, who was hospitalized because of " motor regression with mental retardation for 5 days" at 1 year old.The manifestations of the patient were extrapyramidal symptoms, regression of motor development and seizures.The level of urinary sulfites in the patient was increased.Magnetic resonance imaging (MRI) features were bilateral pallidus and substantia nigra.Gene sequencing suggested a pure missense mutation of the sulfite oxidase( SUOX) gene c. 650(exon5)G>A(p.Arg217Gln). In 16 cases of late-onset ISOD, the median age at onset and diagnosis was 10.5 months and 34.0 months, respectively.The common clinical manifestations were hypotonia (13 cases), seizures (10 cases), movement disorders (9 cases), and ectopia lentis (6 cases). The most common brain MRI feature was pallidus changes (11 cases), followed by lesions of substantia nigra (5 cases), and cerebral atrophy (4 cases). Fourteen cases of late-onset ISOD showed a positive urinary sulfite test.The missense mutation of the SUOX gene was found in 9 cases.It suggested that brain MRI involvement of bilateral pallidus, high excretion of urine sulfites and the missense mutation of the SUOX gene were important diagnostic clues for late-onset ISOD.
ABSTRACT
Abstract Isolated sulfite oxidase deficiency (ISOD) is a devastating, neurometabolic disorder caused by mutations in the SUOX gene necessary for the final step in the sulfur-containing amino acid catabolic pathway. Patients classically present in the neonatal period with neurologic manifestations. Biochemical findings include elevated sulfocysteine, low cystine and undetectable homocysteine with normal uric acid levels. Other associated biochemical markers include elevated plasma alpha-aminoadipic semialdehyde and piperideine-6-carboxylic acid. We report a patient with classic neonatal onset ISOD (refractory seizures, hypertonicity, brain abnormalities, pathogenic SUOX mutations). Her clinical course was marked by extreme irritability, prompting the use of a low methionine and cystine diet to decrease toxic metabolites thought to be contributing to her symptoms. Biochemical markers and extreme irritability improved with dietary treatment (methionine=30mg/kg/day). She died of sepsis in early infancy, precluding long term follow-up. This case reviews the potential benefits and limitations of diet therapy in this rare disorder.