Congenital limb deficiency in Japan: A cross-sectional nationwide survey on its epidemiology

Background: Congenital limb deficiency is a rare and intractable disease, which impairs both function and appearance of the limbs. To establish adequate medical care, it is necessary to reveal the actual conditions and problems associated with this disease. However, there have been no extensive epidemiological surveys in Japan addressing this disease. This is the first nationwide epidemiological survey of congenital limb deficiency in this country. Methods: With the cooperation of epidemiology experts, we performed a two-stage nationwide survey to estimate the number of patients with congenital limb deficiency and reveal basic patient features. We targeted orthopaedic surgery, paediatric, and plastic surgery departments. Hospitals were categorized according to the institution type and the number of hospital beds; hospitals were randomly selected from these categories. We selected 2283 departments from a total 7825 departments throughout Japan. In this study, we defined congenital limb deficiency as partial or total absence of the limbs, proximal to the proximal interphalangeal joint of the fingers/lesser toes or interphalangeal joint of the thumb/great toe. We distributed the first survey querying the number of initial patient visits from January 2014 to December 2015. Targets of the second survey were departments that reported one or more initial patient visits in the first survey. Results: In the first survey, 1767 departments responded (response rate: 77.4%). Among them, 161 departments reported one or more initial patient visits. We conducted the second survey among these 161 departments, of which 96 departments responded (response rate: 59.6%). The estimated number of initial visits by patients with congenital limb deficiency was 417 (95% confidence interval: 339-495) per year in 2014 and 2015. The estimated prevalence of congenital limb deficiency in Japan was 4.15 (95% confidence interval: 3.37-4.93) per 10,000 live births. The sex ratio was 1.40. Upper limbs were more affected than lower limbs. Conclusions: We revealed the estimated number of initial patient visits per year and birth prevalence of congenital limb deficiency in Japan. Our results will contribute to establishing the disease concept and grades of severity of congenital limb deficiency.