Mutation analysis of SUOX in isolated sulfite oxidase deficiency with ectopia lentis as the presenting feature: insights into genotype-phenotype correlation

Orphanet J Rare Dis. 2022 Oct 27;17(1):392. doi: 10.1186/s13023-022-02544-x.


Background: Isolated sulfite oxidase deficiency (ISOD) caused by sulfite oxidase gene (SUOX) mutations is a rare neurometabolic disease associated with ectopia lentis (EL). However, few genotype-phenotype correlations have been established yet.

Methods: Potentially pathogenic SUOX mutations were screened from a Chinese cohort of congenital EL using panel-based next-generation sequencing and analyzed with multiple bioinformatics tools. The genotype-phenotype correlations were evaluated via a systematic review of SUOX mutations within our data and from the literature.

Results: A novel paternal missense mutation, c.205G > C (p.A69P), and a recurrent maternal nonsense mutation, c.1200 C > G (p.Y400*), of SUOX were identified in a 4-year-old boy from 312 probands. The biochemical assays manifested elevated urine sulfite and S-sulfocysteine accompanied by decreased homocysteine in the blood. The patient had bilateral EL and normal fundus, yet minimal neurological involvement and normal brain structure. Molecular modeling simulation revealed the p.A69P mutant had an unstable structure but an unchanged affinity for sulfite, while the truncated p.Y400* mutant showed decreased binding capacity. Genotype-phenotype analysis demonstrated patients with biallelic missense mutations had milder symptoms (P = 0.023), later age of onset (P < 0.001), and a higher incidence of regression (P = 0.017) than other genotypes. No correlations were found regarding EL and other neurological symptoms.

Conclusion: The data from this study not only enrich the known mutation spectrum of SUOX but also suggest that missense mutations are associated with mild and atypical symptoms.

Keywords: Genotype–phenotype correlation; Isolated sulfite oxidase deficiency; Neurometabolic disorder; SUOX; ectopia lentis.

Publication types

  • Systematic Review
  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ectopia Lentis*
  • Genetic Association Studies
  • Humans
  • Mutation / genetics
  • Oxidoreductases Acting on Sulfur Group Donors / genetics
  • Sulfites


  • Sulfites
  • SUOX protein, human
  • Oxidoreductases Acting on Sulfur Group Donors

Supplementary concepts

  • Sulfite oxidase deficiency