MON-252 A (Geni)Tale of Two Diagnosis: Congenital Clitoromegaly with Concurrent Congenital Adrenal Hyperplasia and Mosaic Turner Syndrome

Abstract Disclosure: A.T. Tisler: None. E.A. Copenhaver: None. S. Menon: None. Introduction: Clitoromegaly in a newborn with otherwise typically appearing female genitalia indicates exposure to excess androgens in fetal life. Congenital Adrenal Hyperplasia (CAH) is the most common cause of virilization at birth. Turner syndrome (TS) does not usually present with atypical genital appearance. Clinical Case: Term infant born to non-consanguineous parents was noted to have clitoromegaly (length 1.5 cm, width 1 cm). Pregnancy was complicated by gestational hypertension and treated hypothyroidism. Genital exam revealed separate urethral meatus and vaginal opening without palpable gonads (Prader Stage II). No syndromic features noted. Pelvic ultrasound showed uterus and fallopian tubes but could not visualize ovaries. Due to a high clinical suspicion for CAH, initial labs were sent including a CAH panel after which empiric hydrocortisone and fludrocortisone were started. Electrolytes and blood sugars remained normal. Prior to receiving results of CAH testing, karyotype resulted as [45,XO(3)/46,XX(17)], consistent with mosaic TS. Renal ultrasound was normal. Echocardiogram showed a small atrial septal defect, mildly dilated ascending aorta and trivial mitral regurgitation. FISH for Y chromosome material (SRY, Y centromere) was considered as a potential cause of clitoromegaly but resulted negative. AMH was 0.34 ng/mL. State newborn screen was negative for CAH, but the result was unreliable as it was collected after initiation of steroids. Finally, the CAH panel resulted showing elevated 17-OHP: 1540 ng/dl. This level is more congruent with non-classical CAH, which does not typically result in clitoromegaly at birth. To clarify the diagnosis, a 250 mcg cosyntropin stimulation test was performed after holding steroids for a week. Labs drawn 60 minutes later confirmed classical CAH secondary to 21-hydroxylase deficiency (post stimulation 17-OHP: 82334 ng/dl). Genetic analysis identified biallelic pathogenic deletions of CYP21A2 gene, consistent with salt wasting CAH. Hydrocortisone dose was progressively lowered based on suppressed adrenal hormone levels and poor linear growth. At 18 months of age growth has improved, and she is only requiring 4.5 mg/m2/day hydrocortisone and 0.1 mg/day fludrocortisone for adequate CAH management. Conclusions: Establishing the cause of clitoromegaly and hyperandrogenemia in this newborn with concurrent classical CAH and mosaic TS proved challenging. Few prior published case reports describe these concurrent diagnoses. Current TS guidelines recommend looking for Y chromosome material if masculinizing features develop. This case underlines the value of including CAH in the differential diagnosis as another potential cause of virilization in patients with TS. The concurrence of CAH and TS poses added complexity for clinical management due to overlapping impact on linear growth, puberty, and reproductive function. Presentation: Monday, July 14, 2025