Abstract
To provide a better healthcare system for patients with mitochondrial diseases, it is important to understand the basic epidemiology of these conditions, including the number of patients affected. However, little information about them has appeared in Japan to date. To gather data of patients with mitochondrial diseases, we estimated the number of patients with mitochondrial diseases from April 2018 through March 2019 using a national Japanese health care claims database, the National Database (NDB). Further, we calculated the prevalence of patients, and sex ratio, age class, and geographical distribution. From April 2018 through March 2019, the number of patients with mitochondrial diseases was 3,629, and the prevalence was 2.9 (95% confidence interval [CI], 2.8-3.0) per 100,000 general population. The ratio of females and males was 53 to 47, and the most frequent age class was 40-49 years old. Tokyo had the greatest number of patients with mitochondrial diseases, at 477, whereas Yamanashi had the fewest, at 13. Kagoshima had the highest prevalence of patients with mitochondrial diseases, 8.4 (95% CI, 7.1-10.0) per 100,000 population, whereas Yamanashi had the lowest, 1.6 (95% CI, 0.8-2.7). The number of patients with mitochondrial diseases estimated by this study, 3,269, was more than double that indicated by the Japanese government. This result may imply that about half of all patients are overlooked for reasons such as low severity of illness, suggesting that the Japanese healthcare system needs to provide additional support for these patients.
Highlights
Mitochondrial diseases are caused by nuclear or mitochondrial DNA mutations, and patients vary in age of onset, sex, race, affected organ, severity, and prognosis.[1–3] While mitochondrial diseases were long thought to be rare, recent reports[4–19] have suggested that the prevalence of patients in the general population is higher than originally thought
Definition of mitochondrial diseases The following diagnoses were defined as mitochondrial diseases: Pearson syndrome; pyruvate dehydrogenase complex (PDHC) deficiency (E744); mitochondrial disorders (E888); MELAS (E888); myoclonus epilepsy associated with ragged-red fibers (MERRF) (E888); mitochondrial neurogastrointestinal encephalopathy (MNGIE) (E888); mitochondrial cardiomyopathy (E888); mitochondrial hepatopathy (E888); mitochondrial diabetes (E888); Leigh syndrome (LS) (G318); Alpers’ syndrome (G318); mitochondrial encephalomyopathy (G713); mitochondrial myopathy (G713); Leber’s hereditary optic neuropathy (LHON) (H472); chronic progressive external ophthalmoplegia (CPEO) (H494); and Kearns-Sayre syndrome (KSS) (H498)
Number of patients and prevalence of mitochondrial diseases Within the study period, there were fewer male patients with mitochondrial diseases than female patients (47 vs 53; 95% confidence intervals (CIs) for female ratio, 0.51–0.54), and the majority of patients fell within the age class 0–9 years old (Table 1)
Summary
Mitochondrial diseases are caused by nuclear or mitochondrial DNA mutations, and patients vary in age of onset, sex, race, affected organ, severity, and prognosis.[1–3] While mitochondrial diseases were long thought to be rare, recent reports[4–19] have suggested that the prevalence of patients in the general population is higher than originally thought. Mitochondrial diseases are caused by nuclear or mitochondrial DNA mutations, and patients vary in age of onset, sex, race, affected organ, severity, and prognosis.[1–3]. While mitochondrial diseases were long thought to be rare, recent reports[4–19] have suggested that the prevalence of patients in the general population is higher than originally thought. While there are few reports of mitochondrial diseases in Japan,[17,18] a questionnaire study reported a prevalence of 0.18 per 100,000 general population.[18]. This study was limited to mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), which comprise only a proportion of mitochondrial diseases. The prevalence of overall mitochondrial diseases in Japan remains unclear. To provide a better healthcare system for patients with mitochondrial diseases, it is important to understand the basic epidemiology of these conditions, including the number of patients affected. Little information about them has appeared in Japan to date
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