POSSIBILE DIFETTO DELLA PERMEABILITA CELLULARE AL CALCIO IN UN CASO DI PSEUDOIPOPARATIROIDISMO

We report a case of PHP with renal response to PTH infusion different from those reported in literature. A child is reported who shows the somatic features of Albright osteodystrophy. A generalized and marked osteoporosis and short metacarpals are evident to roentgenograms of the hands. We have studied the renal response after PTH infusion in agreement with the work of Aurbach et al., evaluating the variation of urinary cyclic-AMP (U-cAMP) and phosphaturia. The data obtained show that U-cAMP values in basal conditions are below the control values, like the values of subjects with PHP type I and II reported in literature. The range of U-cAMP values after PTH infusion in different conditions (with and without vitamin D therapy) shows a normal function of PTH-specific adenyl-cyclase receptor system. Stimulation with PTH infusion shows a lack of phosphaturic response when the patient was not in vitamin D therapy, while I.V. calcium infusion makes normal the phospaturic response after PTH infusion. The last study we have done shows that it is possible in our patient to obtain normal U-cAMP and phosphaturia values with simple calcium infusion. The altered renal response after PTH infusion we found in our patient is thought to be the consequence of a defect of cell-membrane permeability to calcium that can be overcome by increasing the extracellular calcium concentration.