Primary adrenal insufficiency caused by pseudo-neonatal adrenoleukodystrophy associated with biallelic ACOX1 mutations.

Background: Peroxisomal fatty acyl-CoA oxidase 1, encoded by ACOX1, initiates and limits the rate of beta-oxidation of very long-chain fatty acids (VLCFA). Biallelic ACOX1 mutations cause pseudo-neonatal adrenoleukodystrophy (PNALD). Primary adrenal insufficiency (PAI) has not been clearly characterized in the 34 PNALD patients reported to date.

Objective: Characterizing PAI in a patient and her cousin with PNALD.

Methods: Clinical data were recorded, and molecular etiologies were investigated using next-generation sequencing panels and 750K microarray. Plasma steroids and VLCFAs were measured via mass spectrometry.

Results: A 1.5-year-old female patient was evaluated for PAI due to hyperpigmentation, hypoglycemia, hyponatremia and hyperkalemia. She had a history of severe neonatal-onset hypotonia, seizures, psychomotor/developmental delay, and neurological regression. Molecular studies revealed a homozygous deletion encompassing exons 13 and 14 of the ACOX1 gene. Biochemical analysis revealed accumulation of saturated VLCFA. Cranial magnetic resonance imaging showed T2 high-intensity areas in bilateral centrum semiovale, basal ganglia, brainstem and cerebellar white matter. High plasma ACTH, low cortisol and steroid precursors along with high plasma renin activity were compatible with a PAI other than congenital adrenal hyperplasia (non-CAH). Abdominal computerized tomography demonstrated bilateral adrenal atrophy. The cousin of the patient with PNALD developed non-CAH PAI at 7 months of age.

Conclusion: Adrenal insufficiency should be considered in the phenotypic spectrum of peroxisomal disorders. Fatty acyl-CoA oxidase 1 deficiency may emerge as a peroxisomal etiology of non-CAH PAI.