Clinical Guidance

The number of individuals with confirmed pathogenic variants in SUOX is too small to make any conclusive genotype-phenotype correlations.

Source: GeneReviews — "Isolated Sulfite Oxidase Deficiency"

Diagnostic Criteria

Suggestive Findings

Classic early-onset (severe) and late-onset (mild) isolated sulfite oxidase deficiency (ISOD) should be suspected in infants with the following clinical, neuroimaging, and supportive laboratory findings.

Clinical Features

Classic ISOD

Source: GeneReviews — "Isolated Sulfite Oxidase Deficiency"

Differential Diagnosis

Table 2. Disorders to Consider in the Differential Diagnosis of Isolated Sulfite Oxidase Deficiency (ISOD)

Management Guidelines

Evaluations Following Initial Diagnosis

To establish the extent of disease and/or needs in an individual with a diagnosis of isolated sulfite oxidase deficiency (ISOD), the following evaluations are recommended:

• Complete neurologic assessment by a pediatric neurologist

• Formal developmental assessment

• Ophthalmologic evaluation

• EEG/video EEG to monitor seizures

• Assessment of feeding and nutrition and appropriate intervention

• Consultation with a clinical geneticist and/or genetic counselor

Treatment of Manifestations

To date, no definitive treatment for ISOD has been identified. Symptomatic management by a multidisciplinary team consisting of specialists in neurology, nutrition, gastroenterology, pulmonary medicine, physiotherapy, and orthopedics is recommended. Management includes the following:

• Appropriate medications for management of seizures and spasticity

• Early consideration of gastrostomy tube placement to manage difficulties with swallowing to assure adequate caloric intake and reduce the risk of aspiration.

• Appropriate management of vomiting, gastroesophageal reflux disease, and aspiration pneumonia

• Chest physiotherapy to prevent respiratory complications

• Sleep studies to assess nocturnal hypoventilation and institute appropriate interventions

• Assessment for scoliosis

The following treatment modalities have been tried with minimal success:

Source: GeneReviews — "Isolated Sulfite Oxidase Deficiency"

Therapies Under Investigation

Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.

Source: GeneReviews — "Isolated Sulfite Oxidase Deficiency"

Surveillance Guidelines

Periodic assessment by the multidisciplinary team with particular attention to the following:

• Nutritional status

• Neurologic status including evaluation of dosages of anti-seizure medication and their side effects

• Degree of spasticity and related complications, including scoliosis

• Periodic sleep studies

Source: GeneReviews — "Isolated Sulfite Oxidase Deficiency"