Multiple renal tubular dysfunctions accompanying vitamin D deficiency rickets

A six-month-old girl with florid hypocalcemic rickets demonstrated glucosuria, aminoaciduria, hyperphosphaturia and type 2 ('proximal') renal tubuar acidosis. Four weeks of therapy with vitamin D and calcium brought about normalization of low serum calcium and phosphate concentrations, as well as a marked fall in elevated serum parathyroid hormone (PTH) level. During this period, tubular glucose, phosphate and bicarbonate transport returned to normal, although aminoaciduria persisted. When re-examined after six months, rickets had healed completely and aminoaciduria had also disappeared. It is suggested that the renal tubular dysfunctions were secondary to hyperparathyroidism, to which amino acid transport may be most sensitive. However, a direct effect of vitamin D deficiency or of phosphate depletion on tubular transport can not be ruled out.