Epidemiology of brachydactyly type A3 in China: a nationwide multicentre population-based study among children aged 3-17 years.

Abstract

This study aimed to investigate the prevalence of brachydactyly type A3 (BDA3) and its associated epiphysial development abnormalities in Chinese children aged 3-17 years, and to explore differences based on gender, region and urban-rural demographics. Cross-sectional study. The study was conducted across 14 provinces (28 survey sites) in China, as part of a nationwide investigation on skeletal maturation. The population was selected using multistage stratified randomised cluster sampling. A total of 17 850 children (8856 boys and 8994 girls) aged 3-17 years participated. The cohort was drawn from a large-scale survey conducted between 2019 and 2021. Selection criteria included children with no visible clinodactyly or hand function impairments. Non-dominant hand-wrist radiographs were obtained using a portable X-ray device. A retrospective analysis of these radiographs was performed to identify BDA3 and epiphysial development abnormalities. Prevalence rates were calculated and compared across gender, regional and urban-rural groups. The overall prevalence of BDA3 was 10.0%, with a higher prevalence in girls (12.9% vs 7.1%; p<0.001). The northern region exhibited a higher prevalence compared with the southern region (11.5% vs 8.6%; p<0.001). No significant differences were observed between urban and rural areas (10.3% vs 9.8%; p=0.32). Among the BDA3 phenotypes, brachymesophalangia-5 with cone-epiphysis of mid-5 (BMP5) and BMP5 alone had prevalences of 3.6% and 6.4%, respectively. Both phenotypes were more common in girls compared with boys (p<0.001 for both). This nationwide, multicentre study provides the first national epidemiologic data on BDA3 and associated epiphysial features in Chinese children and adolescents, establishing a prevalence of 10.0%. This baseline supports counselling that a straight, well-functioning short fifth finger is a common anatomic variant and may help reduce unnecessary concern.