ABSTRACT
Early-onset progressive encephalopathy is a lethal encephalopathy caused by NAXE gene mutations. This paper reports the clinical and genetic features of a patient with early-onset progressive encephalopathy. A 4-year-old boy admitted to the hospital had repeated walking instability and limb weakness for 2 years. The patient and his elder brother (already dead) had clinical onset at 2 years of age. Both of them showed symptoms such as strabismus, ataxia, reduced muscle tone, delayed development, and repeated respiratory failure after infection. The NAXE gene of the patient showed new compound heterozygous mutations, i.e., c.255 (exon 2) A>T from his mother and c.361 (exon 3) G>A from his father. The NAXE gene encodes an epimerase that is essential for the repair of cellular metabolites of NADHX and NADPHX. This disease is associated with a deficiency of the mitochondrial NAD(P)HX repair system. Patients usually have rapid disease progression. They are also quite likely to have respiratory failure immediately after infection.