Evaluation of neurofibromatosis type 1 progression using a nationwide registry of patients who submitted claims for medical expense subsidies in Japan between 2008 and 2012.

backgroundNo study to date has followed disease progression in patients with neurofibromatosis type 1 (NF1), including the incidence of various manifestations, using a national registry. Here we examined the state of NF1 progression using a nationwide registry of patients who submitted claims to receive medical expense subsidies for NF1 in Japan over a five-year period. A total of 342 eligible patients (194 females and 148 males) with NF1 who newly submitted claims for medical expense subsidies in Japan in 2008 were followed until 2012.

resultsMore than half of the patients were classified as Stage 5 in 2008. Of the eligible patients, 205 (60%) submitted claims to renew the subsidies between 2009 and 2012. During the study period, NF1 stage progressed in 30 patients, yielding an overall stage progression rate of 19% and progression incidence rate per 100 person-years of 12.2. Both stage progression rate and progression incidence rate were the highest in the 0-19 year age group at the time of registration and, as compared to other age groups, progression of neurological and bone manifestations was more prevalent in this age group.

conclusionsThe progression of neurological and bone manifestations was more prevalent in the 0-19 year age group compared to other age groups. The registry we used in the present study is useful for understanding the characteristics of patients with uncommon conditions, such as NF1. Our findings also highlight the feasibility of conducting quality research using registries of patients with rare diseases, such as NF1, that were not designed specifically for scientific research.