# Progressive encephalopathy associated with novel compound heterozygous NAXE mutations in a Chinese patient: case report and literature review

## TL;DR

A Chinese child with a rare NAXE gene disorder showed a milder form of the disease, expanding understanding of its symptoms and the need for early genetic testing.

## Contribution

The paper reports a novel compound heterozygous NAXE mutation associated with a milder disease phenotype.

## Key findings

- Compound heterozygous NAXE mutations (c.733A > C and c.389A > C) were identified in a patient with milder encephalopathy.
- The patient showed near-complete motor recovery after treatment with NAD + precursors and immunomodulatory therapies.
- The case highlights the importance of genetic testing for early diagnosis of NAXE-related encephalopathy.

## Abstract

NAD(P)HX epimerase (NAXE) deficiency is a rare, often fatal, autosomal recessive neurometabolic disorder of early childhood, characterized by acute neurological regression triggered by febrile illness. Here, we report a case with compound heterozygous NAXE mutations (c.733A > C and c.389A > C) associated with a milder phenotype, thereby expanding the known disease spectrum.

A previously healthy 19-month-old girl presented with acute neurological regression after a high-grade fever, losing motor skills and exhibiting lethargy. Initial investigations showed leukocytosis, elevated C-reactive protein, and MRI findings of sulcal/cisternal widening and spinal cord signal changes. Given the unexplained encephalopathy, whole-exome sequencing was performed, which identified compound heterozygous NAXE mutations, confirming the diagnosis. Management included intravenous immunoglobulin, corticosteroids, and NAD + precursors. Neurological improvement was observed during the hospital course, and near-complete motor recovery was achieved by the 11-month follow-up.

This case underscores the need to consider NAXE-related encephalopathy in children with fever-induced acute neurological decline. The discovery of a novel compound heterozygous variant combination [c.389A > C [p.His130Pro] and c.733A > C [p.Lys245Gln]] defines a milder phenotypic spectrum and mandates early genetic testing for timely diagnosis and prognostic insight. Importantly, given the single-case nature of this observation, conclusion regarding treatment efficacy remains hypothesis-generating and require validation in additional cases.