Skeletal manifestations of moderate phosphate diabetes

Six patients, with vertebral osteoporosis and reflex sympathetic algodystrophy syndrome of the lower limbs, due to moderate diabetes, are presented. Osteoporosis was documented by low CT scan bone density and moderate decrease of bone trabecular volume. Histomorphometric studies found a mild increase of resorption areas. All patients had unremarkable serum phosphorus level (mean: 0.91 +/- 0.13) but increase of urinary phosphorus excretion was documented by phosphate clearance higher than 20ml/mm, phosphate tubular reabsorption lower than 80% and TmPo4/GFR lower than 0.8mmol/l. Phosphate clearance and phosphate tubular reabsorption are studied in two control groups. Mild phosphate diabetes, of unknown incidence and prevalence (need for prospective studies) may be the vector of osteoporosis, vertebral and peripheral. The diagnosis of PD requires determination of phosphate clearance, phosphate tubular reabsorption, TmPo4/GFR and these tests may be useful in the diagnostic work up of bone demineralization disorders. We thought that osteoporosis could be the result of progressive dissolution of bone apatite crystals necessary to maintain normal or sub-normal blood phosphate level in spite of the phosphate diabetes.