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Duchenne (DMD) and other forms of muscular dystrophy (MD) are collectively rare and affect approx imately 20 per 100,000 people. The on-going development of exon skipping and other novel therapies for DMD is expected to lead to improvements in motor function prognosis. However, improvements in motor dysfunction with these novel therapies are associated with the risk of increase in cardiac burden. Development of therapies to improve cardiac function, therefore, is an urgent issue. This single-arm, open-label, multicenter study will include 20 patients with MD aged 13 years or older. Tranilast, a transient receptor potential cation channel subfamily V member 2 (TRPV2) inhibitor, will be administered orally for a period of 28 weeks at a dose of 300 mg/day divided into three daily doses. If consent to continue administration is obtained at 28 weeks, the drug will be administered for an additional 116 weeks. The primary outcome will be the change in brain natriuretic peptide (BNP) at 6 months after the start of administration compared to baseline. Tranilast is an anti-allergy agent that was developed in Japan. It has been used in a large number of clinical cases, including pediatric cases, and has been shown to be safe. We expect this study to provide basic data for developing new treatment method in cardiomyopathy/skeletal myopathy using TRPV2 inhibitors. Moreover, such therapies may also be effective in treating general heart failure without MD. Therefore, if the effectiveness of TRPV2 inhibitors could be confirmed in this study, great social and economic benefits could be achieved.

We report a 14-year-old Japanese boy who has had asymptomatic, multiple, reddish-brown macules and petechiae distributed segmentally only in the right lower extremity for the last 6 months. Histological examination showed a perivascular lymphohistiocytic infiltrate in the papillary dermis, extravasation of red blood cells, and hemosiderin deposition. Treatment with tranilast and topical corticosteroid was dramatically effective. Although the histological findings were compatible with those of Schamberg disease, this case was unusual because the patient was very young and only one extremity was affected.

Nephrogenic diabetes insipidus (NDI) occurred in a 43-year-old woman who had received lobenzarit disodium for the treatment of rheumatoid arthritis (RA). Her urine output was initially 3 l/day and urine osmolarity was 203 mOsm/l. Based on a sodium chloride loading test and a vasopressin loading test, she was diagnosed as having lobenzarit-induced NDI. Seven days after the cessation of the use of lobenzarit disodium, polydipsia and polyuria disappeared, and the vasopressin test showed a normal response. These findings suggest that lobenzarit induces a reversible form of NDI as a side effect. The reports of lobenzarit-induced NDI in Japan during the past seven years are also reviewed.