Chimeric CYP21A1P/CYP21A2 Genes in 21-Hydroxylase Deficiency Detected by Long-Read Sequencing and Phenotypes Correlation.

Summary

In 869 patients with 21‑OHD, long-read sequencing identified 10 CYP21A1P/CYP21A2 chimera types (including a novel CH‑10), with CH‑1 being most common. Haplotype analysis suggested no single founder effect, and in vitro assays confirmed very low residual activity for novel variants, supporting strong genotype–phenotype correlations.

Key Findings

• Identified 10 CYP21A1P/CYP21A2 chimera types across 119 alleles using long-read sequencing, including a novel CH‑10.
• CH‑1 was the most prevalent chimera (50.4%). Haplotype analysis revealed diverse haplotypes, arguing against a founder effect.
• In vitro assays showed very low residual activity for novel variants (e.g., p.L100P, p.L301V), aligning with simple virilizing phenotypes; genotype–phenotype consistency was ~79–84%.

Clinical Implications

Supports integrating long-read sequencing into diagnostic workflows for CAH to improve detection of chimeras/deletions, inform genetic counseling, and guide individualized management.

Limitations

• Retrospective single-center design may limit generalizability
• Clinical outcome data beyond genotype–phenotype correlation were limited

Future Directions

Broaden implementation of long-read sequencing across diverse populations and link genetic architecture with treatment response and long-term outcomes.