Infections Can Trigger Sudden Deterioration in Children; High-Dose Vitamin B3 Offers a Treatment Clue for NAXD Deficiency

Some children with defects in the NAXD gene appear healthy at birth, yet a common infection can cause their neurological or cardiac function to deteriorate rapidly. An international research team has now reported nine newly diagnosed cases, including four children treated with high-dose vitamin B3 who survived subsequent fevers or infections, providing an initial treatment clue for this often-fatal, ultra-rare disease.

The study, published in the Journal of Inherited Metabolic Disease, broadens the clinical spectrum of NAXD deficiency. Of the nine patients, four experienced neurological deterioration after infection, including seizures and developmental delay; another four presented primarily with severe cardiac problems, while one fetus developed severe neurodegeneration before birth and was ultimately stillborn. Two patients developed the disease after COVID-19 infection, also highlighting that febrile illnesses may become a dangerous turning point.

NAXD is responsible for repairing NAD(P)H cofactors damaged during cellular metabolism, helping to maintain energy production. When both copies of the NAXD gene carry pathogenic variants, damaged cofactors may accumulate, making it particularly difficult for cells to continue functioning under stresses such as infection and fever. The researchers hypothesize that niacin in high-dose vitamin B3 may support NAD-related metabolic pathways and thereby increase cells’ ability to withstand metabolic stress.

The case and experimental findings also show a preliminary genotype–phenotype association: some variants in the catalytic region were more often associated with neurological symptoms, whereas variants in the mitochondrial targeting sequence were observed in cardiac cases. After testing four missense variants, the team found that they impaired the solubility, enzymatic activity, or thermal stability of the NAXD protein; fibroblasts from three patients also showed increased levels of damaged cofactors and reduced NAXD protein.

All four patients treated with niacin were still alive at the time of reporting and had experienced at least one febrile episode. However, this was not a randomized controlled trial, and there was no comparison group of untreated patients with comparable disease severity. The number of patients was extremely small, and their variants and clinical manifestations were inconsistent; therefore, it can currently be said only that treatment coincided with a more favorable disease course, not that niacin prevented deterioration. Long-term safety, appropriate dosing, the timing of treatment initiation, and whether different subtypes benefit equally all require systematic follow-up.

The findings also carry implications for diagnosis. If clinicians look for NAXD deficiency only in children with post-infectious encephalopathy, they may miss patients whose main manifestations are heart failure or prenatal neurodegeneration; and if the treatment hypothesis proves valid, the timing of disease recognition will directly affect the opportunity for intervention. High-dose niacin is also different from ordinary nutritional supplementation, and case reports cannot serve as a basis for self-administration.

The research team is also exploring whether existing drugs can improve cellular energy metabolism. A conference abstract released in March stated that researchers had screened 4,222 compounds approved by the U.S. FDA and identified 11 preliminary candidates, which are now undergoing further testing in cell and animal models. This drug-repurposing approach remains at an early stage; the more urgent task at present is to identify more patients, establish natural-history data, and use consistent treatment and follow-up methods to determine whether vitamin B3 truly changes survival and neurological and cardiac outcomes.