Vitamin-responsive inherited diseases are a rare set of conditions that may be underdiagnosed in adults. In a recent review article published in JAMA Neurology, researchers outlined clinical situations when diagnostic tests should be conducted for vitamin-responsive inherited diseases and when vitamins should be administered to ensure optimal disease outcomes.
According to the study researchers, the pathophysiology of vitamin-responsive diseases falls into 4 groups: patients with impaired cofactor synthesis from vitamins; impaired transport of vitamins; enzymatic defect requiring a vitamin derived cofactor; and a secondary vitamin defect caused by abnormalities not associated with a gene defect involved in the metabolism of vitamins.
Tools available to assist in the diagnostic process of vitamin-responsive inherited diseases include clinically oriented gene panels, whole-exome sequencing, and whole genome sequencing. In many different clinical situations, a valid diagnostic approach includes a first-line or parallel biochemical strategy.
The first-line or parallel biochemical diagnostic approach may be largely appropriate, considering some clinical situations do not always suggest a genetic causative factor up front. This leads to the undertaking of several investigations to determine the causative factor.
Genetic testing has its limitations in vitamin-responsive diseases, according to the study researchers. For instance, the time it takes to obtain genetic testing results may cause delays in vitamin administration in situations where prompt therapy initiation is imperative. Genetic testing may also lack the ability to detect or interpret different variants. Lastly, genetic testing is not readily available in certain regions, while vitamins are plentiful and can be accessed easily across the world.
Certain conditions where vitamin administration may be appropriate in the context of vitamin responsive-inherited diseases include muscle and nerve diseases, Hartnup disorder, biotinidase deficiency, and Parkinsonism.
The field studying vitamin responsive inherited diseases is rapidly expanding. Given its evolving nature, it may be likely that some inherited vitamin-responsive diseases previously reported only in children may now start to be documented in adults.
As such, the researchers of this review concluded that a vitamin supplementation trial is needed “in patients with phenotypes similar or close to a known vitamin-responsive genetic disease, even if classical biochemical and genetic investigations (including whole-exome and whole-genome sequencing) have negative results.”
Mandia D, Shor N, Benoist JF, Nadjar Y. Adolescent-onset and adult-onset vitamin-responsive neurogenetic diseases: A review. JAMA Neurol. 2021;78(4):483-490. doi:10.1001/jamaneurol.2020.4911