Urine Sorbitol and Xylitol for the Diagnosis of Sorbitol Dehydrogenase Deficiency–Related Neuropathy

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BACKGROUND AND OBJECTIVES: is complicated by the presence of a pseudogene. Biochemical testing of serum sorbitol is suggested as a potential biomarker. We report a novel urine biochemical profile of elevated excretion of sorbitol and a second polyol, xylitol, to aid in the identification of individuals with SORD-related neuropathy. METHODS: Patients with confirmed or suspected SORD-related neuropathy were recruited by clinicians from 7 academic medical centers and 1 nonprofit specialty care center. Urine was analyzed by a clinically validated, gas chromatography-mass spectrometry assay to measure sorbitol and xylitol excretion. Over 700 reference samples were evaluated from residual clinical samples. Clinical and molecular findings were gathered using a standardized questionnaire. RESULTS: variant detected, whereas normal urine sorbitol/xylitol levels were observed in 11 asymptomatic, heterozygous carriers. DISCUSSION: These data demonstrate the clinical utility of urine sorbitol and xylitol analysis in the screening and diagnosis of SORD deficiency-related neuropathy. In addition, this is the first description of elevated xylitol in SORD deficiency as a clinically informative biomarker, which may increase the specificity of biochemical testing.