17α-hydroxylase deficiency with a novel CYP17A1 mutation: a case report.

Background: 17α-hydroxylase deficiency (17-OHD) represents the rarest subtype of congenital adrenal hyperplasia (CAH), characterized by impaired cortisol and sex hormone synthesis due to CYP17A1 enzyme deficiency. The classic clinical triad includes hypokalemia, drug-resistant hypertension, and sexual infantilism. The lack of prominent prepubertal sexual development characteristics may lead to delayed diagnosis of 17-OHD. This study completely documents a prepubertal child with 17-OHD, characterized by recurrent hypertension, hypokalemia, and respiratory infections, encompassing the entire course from clinical discovery, genetic diagnosis, treatment initiation, to 24-month follow-up. Case Description: A 10-year-old girl presented with recurrent hypokalemia, hypertension, and respiratory tract infections. Hormonal testing revealed pathognomonic features of 17-OHD, including elevated progesterone, undetectable cortisol, suppressed renin activity, elevated mineralocorticoid precursors, and reduced sex hormones. Genetic analysis confirmed CYP17A1 compound heterozygous variants: a novel pathogenic mutation (c.1082T>C: p.L361P), rare exome variant ensemble learner (REVEL) score 0.94, and a known frameshift mutation (c.985_987delinsAA: p. Y329Kfs90), with concurrent 15q11.2 microdeletion. The treatment plan included hydrocortisone, metoprolol, captopril, and potassium supplementation to stabilise blood pressure and serum potassium levels. At the 24-month follow-up, new-onset arrhythmias and non-autoimmune thyroid dysfunction were documented. Conclusions: 17-OHD can present with recurrent hypokalemia, refractory hypertension, and respiratory tract infections in childhood, which are prone to misdiagnosis. Early hormonal testing (such as elevated progesterone and decreased cortisol) and CYP17A1 gene analysis are crucial for diagnosis, and the discovery of the novel mutation (c.1082T>C: p.L361P) enriches its genetic spectrum.