A case of rickets associated with Dent disease in a young Japanese boy

Abstract

Dent disease is X-linked and characterized by low molecular weight proteinuria, hypercalciuria, nephrocalcinosis/nephrolithiasis, renal insufficiency in adulthood and is caused mainly by inactivating mutations in the chloride channel 5 gene (CLCN5). Although rickets is often observed in British patients, it is rather rarely reported in Japanese patients. Therapy and management have not yet been established for Japanese Dent disease patients with rickets. A 1-year-old boy whose brother had already been diagnosed with Dent disease had a very high level of urine β2 microglobulin and findings of nephrocalcinosis on ultrasound. He had bandy legs at age 2 years and X-ray findings of the knee joints were characteristic of rickets. The blood examination demonstrated a high serum alkaline phosphatase level and low serum phosphate level. He had a nonsense mutation of the CLCN5 gene similar to that of his brother. Phosphate supplementation improved his X-ray findings in the knee joints. We must pay attention to emerging rickets in patients with Dent disease. Furthermore, it is necessary to confirm the frequency of rickets in Japanese patients of Dent disease and to establish optimal therapeutic and management strategies.