Specimen:

Urine

Collection Medium:

Minimum:

Preferred Minimum:  1.0 mL urine
Absolute Minimum:  0.3 mL urine

Delivery Instructions:

Submit specimen to laboratory as soon as possible after collection.

Testing Schedule:

Testing performed Monday-Thursday only.

Analytic Time:

2 weeks

Reference Range:

See report

Interpretive Data:

Molybdenum cofactor deficiency and isolated sulfite oxidase deficiency 
are rare inborn errors of metabolism.  Molybdenum cofactor is essential 
for the function of the human enzymes sulfite oxidase, xanthine 
dehydrogenase and aldehyde oxidase.  In patients with either molybdenum 
cofactor deficiency or isolated sulfite oxidase deficiency, clinical 
symptoms can vary in severity and age of onset.  The characteristic 
presentation includes severe seizures, often refractory to 
anticonvulsants, and other neurological abnormalities.  Patients who 
survive the neonatal period may develop dislocated lenses providing an 
additional and more specific diagnostic clue.

S-sulfocysteine is a disease-specific metabolite that accumulates in 
patients with both forms of the deficiency.  Determination of this 
metabolite in urine by our method provides the most reliable indication 
of molybdenum cofactor deficiency and isolated sulfite oxidase 
deficiency.  This test is much preferred over the use of sulfite 
dipstick tests that are only of utility if urine is fresh because 
sulfite is rapidly oxidized to sulfate at room temperature.  
Furthermore, the dipstick test lacks specificity and has been reported 
to give both false positive and negative results.

The S-Sulfocysteine assay should be considered in the work up of 
individuals with neonatal seizures.  A positive result with this assay 
should be confirmed by enzyme measurements in cultured fibroblasts 
and/or DNA testing.

Comments:

Please print, complete and submit the Biochemical Genetics 
Laboratory:  Test Request Form to the lab, with the specimen and the 
A-1a Miscellaneous Request.

Methodology:

Tandem Mass Spectrometry

CPT Code:

82127, 82570