THU187 Genotype-Phenotype Correlation, Clinical Presentation And Feminizing Surgery In Children With Congenital Adrenal Hyperplasia Due To 21-Hydroxylase Deficiency: A Nationwide Multi-Center Study

Disclosure: M. Lind-Holst: None. A. Berglund: None. M. Duno: None. G. Hvistendahl: None. M. Fossum: None. A. Juul: None. N. Jørgensen: None. K.M. Main: None. C.H. Gravholt: None. D. Hansen: None. Background: Congenital adrenal hyperplasia (CAH) due to 21 hydroxylase deficiency (21OHD) is a common autosomal recessive disorder caused by pathogenic variants in CYP21A2. Genotype cannot always predict severity and clinical consequences, and genotype-phenotype is only well correlated in the most severe clinical cases of CAH. Furthermore, non-classical CAH suffers from non-diagnosis, especially in males. Objective: Describe the genotype-phenotype correlation in Danish children with 21OHD and identify the most frequent pathogenic CYP21A2 variants. We describe the clinical manifestations at time of diagnosis and present data on virilization and feminizing surgery of females, stratified by genotype group during 20 years. Method: A national population-based study of all Danish children diagnosed with 21OHD, combining health registries and medical record data. We identified pathogenic variants in CYP21A2 and genotype-phenotype correlation. Clinical presentation at diagnosis and feminizing surgery in females was stratified by genotype group: Null, A, B, C and D, reflecting the preserved 21-hydroxylase activity in increasing order. Results: Variants frequency of 494 unique alleles: Deletion (31.8%) followed by I2G, Q318X, I172N, V281L, P30L, Cluster-E6, R356W and insT by 25.9%, 9.1%, 8.6%, 8.7%, 6.5%, 1.4%, 1.4% and 0.6%, respectively. Genotype-phenotype correlations: Null: 98%, A: 94%, B: 50%, C: 76%. Overall, 62 of the 159 children (67%) had evidence of pseudo-precocious puberty at time of diagnosis which was the most frequent group of symptoms in genotype group B: 8.2%, C: 23.3% and D: 3.8%. Bone age advancement was significantly more advanced at the time of diagnosis in males compared to females (p=0.0009). The most frequently reported symptom at diagnosis in the genotype group null (n=20) and A (n=31) were: clitoral hypertrophy in females: 62.7%, failure to thrive: 29% and salt-wasting crisis: 22%. Clitoral hypertrophy was also present in genotype group B, C and D and feminizing surgery was performed in 85% of prenatally virilized females and overall in 40% of females at a median age of 0.9 years [IQR 0.5-1.6]. Conclusion: Genotype groups only predict phenotype with high certainty in the null and A genotype groups. In a national cohort evidence of virilization in females and feminizing surgery were observed in every genotype group. Delayed or non-diagnosis in children with SV and NC CAH was substantial, especially in males. We suggest that children with even mild hyperandrogenic symptoms and normal biochemical markers for 21OHD may benefit from genetic testing for CAH to establish a diagnosis. Presentation: Thursday, June 15, 2023