Rare Causes of Pediatric Primary Adrenal Insufficiency: Data from a Large Nationwide Tunisian Cohort.

Context: Primary adrenal insufficiency (PAI), a rare and potentially life-threatening disorder, involves genetic factors in over 80% of pediatric cases. Congenital adrenal hyperplasia (CAH) is common, while the prevalence of other genetic factors varies between countries.

Objective: This study investigated the clinical and molecular genetic characteristics of a Tunisian PAI sub-cohort. Identifying causal variants is crucial for patient care, genetic counseling, follow-up and preventing complications. Determining variant prevalence will help in shaping a cost-effective molecular strategy in a country with limited resources.

Patients and methods: Seventy-four patients from 65 families, with suspected congenital PAI, excluding CAH and autoimmune disease, were recruited. Clinical details were assessed by endocrinologists. Genetic analysis used a candidate gene approach (AAAS, ABCD1) and/or targeted enrichment with focused gene panels and next-generation sequencing (NGS). The pathogenicity of rare variants was assessed on in silico analysis.

Results: The study achieved a diagnostic yield of 86% (56/65 families), confirming 45 patients with Allgrove syndrome (Triple A) and identifying 12 boys with adrenoleukodystrophy. The recurrent Maghreb variant (c.1331+ 1G>A) was identified within the AAAS gene. NGS revealed additional defects, including AAAS and ABCD1 variants in atypical cases (n=3). Other etiologies included MC2R (n = 1), NNT (n = 1), STAR (n = 2, 1 family), MCM4 (n= 1) variants; 14% remained undiagnosed, some with variants of uncertain significance.

Conclusion: This study of Tunisia's largest PAI cohort confirmed the efficacy of the candidate gene approach. NGS significantly increased diagnostic yield (11%) and identified candidate variants. Achieving molecular diagnosis in almost 90% of children has implications for patient management, genetic counseling, monitoring and the prevention of complications.