(SMVTD)

Extremely rare. Autosomal recessive transmission (often biallelic association of two pathogenic variants) of a mutation of the SLC5A6 gene (2p23.3), coding for the Na-dependent transporter of water-soluble multivitamins (B1, B2, B5, B6, B7, B12, folic acid) and lipoate (mitochondrial metabolism). As biotin (cofactor of 5 carboxylases) and pantothenic acid (precursor of CoA) are essential vitamins because they are not synthesized in the human body, any dysfunction of this transporter in the intestinal mucosa and cerebral capillaries leads to variable signs of deficiency.

The clinical presentation is variable, often similar to that of biotinidase deficiency (see this term), depending on the residual activity of the transporter.

A clinical distinction is made between:

1.        a so-called systemic phenotype [MIM 618 973].

-        onset before 2 years of age

-        developmental delay and mental retardation

-        ataxia, convulsions, MRI brain abnormalities

-        gastrointestinal disorders: diarrhea, episodes of intestinal pseudo-obstruction

-        skin lesions: periorificial dermatitis

-        frequent infections, sometimes accompanied by metabolic crisis with acidosis or cardiac failure

-        peripheral motor neuropathy

2. a so-called motor neuropathic phenotype [MIM 619 903] (COMNB for Chilhood Onset Biotin-responsive peripheral Motor Neuropathy

-        later onset

-        peripheral motor neuropathy (demyelination)

In all cases: urine excretion of large quantities of 3-hydroxyisovaleric acid

Treatment: intake of water-soluble vitamins by IV route or very high doses by mouth.

Anesthetic implications: 

check adequacy of vitamin B supplementation ; anesthetic management according to the organs involved ; in case of motor neuropathy, problematic monitoring of neuromuscular blockade.

References :  

-          Montomoli M, Vetro A, Tubili F, Donati MA, Daniotti M, Pochiero F et al.
A novel SLC5A6 homozygous variant in a family with multivitamin-dependent neurometabolic disorder: phenotype expansion and long-term follow-up.
Eur J of Medical Genetics 2023 ; 66 : 104808

-        Van Vyve F-X, Mercier N, Papadopoulos  J, Heijmans C, Dessy H, Monestier O, Dewulf . P, Roland D.
A new case of sodium-dependent multivitamin transporter defect occurring as a life-threatening condition responsive to early vitamin supplementation and literature review.
Molecular Genetics & Genomic Medicine, 2024 ; 12, e2388. doi.org/10.1002/mgg3.2388

-        Jiang X, Wang H, Lin Z.
Sodium-dependent multivitamin transporter deficiency.
JAMA Dermatol 2024 ; doi:10.1001/jamadermatol.2024.1845

Updated: August 2024