In vitro uptake of calcium by dermis of patients with pseudoxanthoma elasticum.

The calcification of dermal elastic fibers is a characteristic feature of affected skin from patients with pseudoxanthoma elasticum (PXE). Punch biopsies of normal skin and of affected and unaffected skin from patients with PXE were obtained to study dermal calcification in vitro. Before incubation, the calcium, magnesium, and phosphorus content of normal and PXE unaffected dermis were similar and that of PXE affected dermis was significantly higher. Dermal samples were incubated for 2 and 4 days at 37 degrees C. in a calcium phosphate buffer and the Ca and P content were measured. After 4 days of incubation, both PXE affected and unaffected dermis took up significantly more Ca and PO4 than normal dermis. Thus in vitro uptake study could clearly distinguish between normal and PXE dermis. PXE is a disease of variable expression and mild or subclinical forms are difficult to diagnose. Dermal biopsies from clinicallu normal relatives of patients with PXE were obtained and the in vitro uptake of Ca and PO4 was measured. The results show that several of these individuals had elevated uptakes of Ca and PO4 similar to the unaffected dermis of the PXE patient. The results suggest that this test may be used as a diagnostic aid in the detection of individuals with mild forms of PXE and may be a genetic marker for PXE.