Dent disease is characteristic for the urinary loss of low-molecular-weight proteins and calcium, leading to renal calcification and, in some patients, chronic renal failure. This disorder is caused by loss-of-function mutations in the renal chloride channel gene, CLCN5. The animal model of this disease has demonstrated the possible role of disturbed megalin expression, which is a member of the low-density lipoprotein receptor family and is associated with renal reabsorption of a variety of proteins, in Dent disease. We examined the expression of megalin in the renal tubular epithelium of two unrelated patients with Dent disease. One patient, whose CLCN5 gene was completely deleted, showed significantly decreased staining of megalin compared with controls, while there was no change in another patient with partial deletion of the gene. These results demonstrated that mutation of CLCN5 in some patients with Dent disease may impair the expression of megalin, resulting in abnormal calcium metabolism, manifested as hypercalciuria and nephrocalcinosis.

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Recently, the reemergence of vitamin D deficiency in developed countries has been pointed out. Vitamin D deficiency is diagnosed based on the serum 25-hydroxyvitamin D (25OHD) level. However, its normal range is still controversial, making the diagnosis of vitamin D deficiency difficult. Here, we present seven Japanese patients diagnosed with vitamin D deficiency. Three patients complained of leg bowing, and the other four of tetany. The patients with leg bowing were toddlers. Radiographic surveys demonstrated evidence of rickets. Laboratory findings showed decreased levels of serum inorganic phosphorus and increased levels of alkaline phosphatase (ALP) and intact-parathyroid hormone (iPTH). The serum levels of 25OHD were relatively low, ranging from 13 to 15.2 ng/ml. Of the patients with tetany, three were young infants. Laboratory findings showed decreased levels of serum calcium and increased levels of ALP and iPTH. The serum levels of 25OHD were markedly decreased (below 8 ng/ml). Thus, these results indicate that relatively low levels of 25OHD can cause rickets, a symptom of vitamin D deficiency, and that clinicians should therefore carefully evaluate the levels of 25OHD.

A 12-year-old girl with Alagille syndrome manifested severe hypertension caused by renal artery stenosis in a solitary functioning kidney. Percutaneous transluminal angioplasty (PTA) and stenting was performed, but the hypertension persisted. On the next day, acute renal failure occurred with the administration of angiotensin-converting enzyme inhibitor, and migration of the stent was confirmed by angiography. Thus, a second stent was placed with success. Since then, the hypertension has been controlled with anti-hypertensive medication, and the renal function has recovered to normal range.

CysC-eGFR might already be decreased at school age in children born with ELBW. Renal assessment in regular follow-up examinations is recommended.