A Single Fever Can Trigger Rapid Deterioration: Vitamin B3 Offers a Treatment Lead for NAXD Deficiency

For most children, fever and infection are usually only temporary episodes; for patients with NAXD deficiency, however, they can trigger irreversible neurodegeneration or severe cardiac disease within days. A multinational study published in the Journal of Inherited Metabolic Disease now offers an important but still preliminary lead: four children treated with high-dose nicotinic acid are not only still alive but have also survived multiple subsequent febrile illnesses.

NAXD deficiency, also known as PEBEL2, is caused by biallelic pathogenic variants in the NAXD gene. The normal NAXD enzyme repairs NAD(P)HX, which forms when NADH and NADPH become damaged. These molecules normally participate in cellular energy production and redox reactions; if the damaged products cannot be cleared, they may accumulate and disrupt metabolism. To date, the disease has been observed in only a very small number of families. Its typical course involves rapid deterioration after infection or fever in infancy or early childhood, sometimes leading to early death.

The research team compiled data on nine new patients, showing that the disease presents more variably than previously understood. Four experienced neurological deterioration triggered by fever or illness, while another four primarily developed cardiac disease after illness; the ninth had severe neurodegeneration during the fetal period and ultimately died in a preterm stillbirth. The locations of the variants also showed some correspondence: neurological cases mostly involved the enzyme’s catalytic region, while cardiac cases involved the mitochondrial targeting sequence. However, data from the nine patients are not sufficient to establish definitive rules for predicting genotype and disease course.

Cell and protein experiments provided a partial biological explanation for these clinical differences. The researchers examined four missense variants and found that they reduced the solubility, enzymatic activity, or thermal stability of the NAXD protein; fibroblasts from three patients also showed NAD(P)HX accumulation and reduced NAXD protein levels. This means that the failure to repair damaged metabolic cofactors is no longer merely a genetic inference but is also supported by evidence at the patient-cell level.

Nicotinic acid is a form of vitamin B3 and a precursor used by cells to synthesize NAD-related molecules. The researchers hypothesized that increasing its availability might support cellular function during the metabolic stress caused by infection. All four patients who received high-dose nicotinic acid survived and endured recurrent febrile episodes. This result is also consistent with earlier isolated cases and the direction of animal research, but the study was not a randomized controlled trial and cannot exclude the effects of patient variants, disease severity, treatment timing, or other care measures.

Survival likewise does not mean that existing neurological or cardiac damage has been reversed. The available data do not answer what the optimal dose is, when treatment should begin, how long it should continue, or whether different variants respond in the same way. The number of cases and duration of follow-up are also insufficient to fully assess the hepatic, metabolic, and other long-term risks of high-dose nicotinic acid. The finding should therefore be regarded as a signal supporting formal clinical research, not as a basis for children in general to take vitamin B3 supplements on their own.

The team also identified 11 preliminary candidates among 4,222 compounds approved by the U.S. Food and Drug Administration, which are still being retested in cell and animal models. For this ultra-rare disease, whose patients are geographically dispersed and whose course can change abruptly, the next steps in determining whether nicotinic acid can truly alter the disease course will be early genetic diagnosis, the establishment of multinational patient registries, and the development of consistent treatment and follow-up standards.