Prenatal Brain Abnormalities in Sodium-Dependent Multivitamin Transporter Deficiency

In treatable neurometabolic disorders, early diagnosis and prompt initiation of treatment are key to improved survival and outcomes. Biallelic variants in SLC5A6 cause sodium-dependent multivitamin transporter deficiency (OMIM # 618973), which is treatable with high-dose pantothenic acid, biotin, and alpha lipoic acid. So far, the onset has been postnatal in all reported patients. A review of the prenatal imaging showed ventriculomegaly at 32 weeks of gestation. After birth, the infant exhibited developmental regression. At 6 months of age, he developed acute metabolic shock in the setting of a urinary tract infection. Rapid exome analysis identified compound heterozygous pathogenic variants in SLC5A6 and confirmed the diagnosis of sodium-dependent multivitamin transporter deficiency. After the infant was initiated on treatment with high-dose biotin and pantothenic acid, we noted dramatic improvements in the hematological, cutaneous, cardiac, and gastrointestinal symptoms. Although the infant showed no further regression, he continued to have significant psychomotor disability. A review of the findings during pregnancy showed that the infant already had enlarged ventricles in late pregnancy, and neuroimaging on day 12 of birth showed signs of energy failure in late pregnancy. Our review of previously reported patients suggested no clear genotype-phenotype correlations, but there was little intrafamilial variability in disease onset. The present observation, for the first time, provides clinical evidence of a fetal onset in sodium-dependent multivitamin transporter deficiency. The high risk of recurrence and the low intrafamilial variability in disease onset suggest that identification and prenatal treatment in the high-risk group may be of significance.