Delayed diagnosis of familial glucocorticoid deficiency type 4 in a child with epilepsy: a case report and literature review

Objectives Familial glucocorticoid deficiency type 4 (FGD4) is a rare autosomal recessive form of primary adrenal insufficiency caused by biallelic variants in the NNT gene and characterized predominantly by isolated glucocorticoid deficiency. Neurological presentations may obscure the underlying adrenal disorder. We describe a pediatric case with a novel NNT variant not previously associated with FGD4 and review the reported clinical and genetic spectrum. Case presentation A 10-year-old girl presented with a 4-year history of epilepsy and longstanding diffuse hyperpigmentation. A homozygous frameshift variant in NNT (c.645delT; p.Phe215Leufs*17) was identified in the appendix to the previous whole-exome sequencing report and confirmed by Sanger sequencing; both parents were heterozygous carriers. The variant was classified as pathogenic according to ACMG criteria. The patient also had primary hypothyroidism, symptomatic epilepsy, and metabolic encephalopathy. During follow-up with glucocorticoid and thyroxine replacement therapy and continued antiepileptic treatment seizure frequency decreased, hyperpigmentation improved, and communication, attention, and social interaction improved. Conclusions This case expands the mutational spectrum of NNT -related FGD4 and emphasizes the importance of considering adrenal insufficiency in pediatric patients presenting with seizures and hyperpigmentation. Early recognition and diagnosis of adrenal insufficiency enable timely hormone replacement therapy and may reduce the risk of neurological and metabolic complications.