Sulfite Oxidase Deficiency and Molybdenum Cofactor Deficiency Treatment & Management

Updated: Feb 18, 2019
  • Author: Reena Jethva, MD; Chief Editor: Luis O Rohena, MD, PhD, FAAP, FACMG  more...
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Approach Considerations

A multidisciplinary team is recommended for the treatment of sulfite oxidase deficiency and molybdenum cofactor deficiency. While treatment is available for some types of molybdenum cofactor deficiency, no long-term effective therapy is available for other cases. Various medications have been attempted. Supportive symptomatic care may include the following:

  • Medications to manage seizures and spasticity
  • Monitoring and management of gastrointestinal complications (ie, vomiting, gastroesophageal reflux, poor nutrition, aspiration)
  • Monitoring and management of respiratory complications (ie, aspiration pneumonia)

Medical Care

No medical treatments that improve neurologic outcome are known, but cyclic pyranopterin monophosphate (cPMP) has shown promise in the treatment of molybdenum cofactor deficiency type A. Human trials of cysteine-restricted and methionine-restricted diets have been conducted, but the clinical benefits have varied. Low-protein diets have also been attempted.

Intravenous cyclic pyranopterin monophosphate (cPMP) treatment in a patient with MOCS1 deficiency has shown promise. Reduction in sulfite, S-sulfocysteine, thiosulfate, xanthine, and uric acid levels were noted within one week of treatment and a reduction of seizures within two weeks of treatment. The child continued to be developmentally delayed with spastic quadriplegia and hypertonicity. Brain MRI demonstrated cerebral atrophy with a characteristic cystic appearance. [10] A child who was prenatally diagnosed with sulfite oxidase deficiency and received early treatment was found to have only mild cognitive delays and normal fine/gross motor delays at 21 months. [5] The FDA has granted breakthrough therapy designation to cPMP replacement.

Nulibry (fosdenopterin) was the first therapy approved by the FDA to reduce the risk of mortality in molybdenum cofactor deficiency (MoCD) Type A patients.

Approval was based on data from 3 clinical trials which compared data from a natural history trial. Efficacy was assessed in a combined analysis of genetically confirmed MoCD Type A patients from Study 1 (n=8), Study 2 (n=1), and Study 3 (n=4) who received substrate replacement therapy with fosdenopterin or recombinant cPMP (rcPMP; same active moiety and biologic activity as fosdenopterin). The probability of survival for the treated group was 84% (95% CI 49%,96%) compared to 55% (95% CI 30%,74%) in the untreated, genotype-matched, historical control group at the three-year mark. The treated group also had a reduced risk of death by 82% compared to the untreated group(HR=0.18, 95% CI 0.04, 0.72). [19]



Involve a metabolic specialist and a neurologist in evaluation and management of individuals with this disorder. Involve other specialists depending on the symptomatic care required for the patient.



Diets restricted in cysteine and methionine have been used in a few cases of sulfite oxidase deficiency. In some reported cases, biochemical improvement has been observed, but clinical improvement has been infrequently reported. The value of these diets and low-protein diets for individuals who present with mild or late cases of this disorder remains to be further studied but may be more effective.

Prospective diet treatment of siblings of known cases has not improved outcome.