Severe renal osteodystrophy without elevated serum immunoreactive parathyroid hormone concentrations in hypomagnesemia due to renal magnesium wasting

An 8 1/2 -year-old girl presented with a long history of seizures, growth retardation, muscle weakness, gait disturbance, and hearing loss. Her evaluation revealed chronic moderate renal failure (serum creatinine 2.2 mg/dL), severe hypocalcemia (5 mg/dL), hyperphosphatemia (8.1 mg/dL), hypomagnesemia (1.5 mg/dL), increased urinary magnesium excretion (2 mg/kg/d), high fractional excretion of magnesium (21.7%), hypokalemia (3.2 mEq/L), and hyperkaliuria (26 mEq/L). Low circulating immunoreactive parathyroid hormone levels for the degree of the hypocalcemia (serum N-parathyroid hormone 212 pg/mL) and severe rickets without evidence of osteitis fibrosa cystica were found. The patient probably has primary renal leak hypomagnesemia (magnesuric hypomagnesemia) which caused impaired secretion of immunoreactive parathyroid hormone leading to severe hypocalcemia and calcium deficiency rickets. Treatment with magnesium and calcium supplements, calcitriol, and aluminum hydroxide resulted in marked clinical, biochemical, and radiologic improvement. Calcium deficiency rickets due to primary or secondary renal magnesium wasting in conjunction with moderate renal failure represents a largely unrecognized metabolic bone disease.