High levels of desmosines in urine and plasma of patients with pseudoxanthoma elasticum.

BACKGROUND: Pseudoxanthoma elasticum (PXE), a rare heritable disorder caused by mutations of the ABCC6 gene, is characterized by fragmentation and mineralization of elastic fibres. We determined the extent of degradation of elastin by measuring and comparing the amount of desmosines in plasma and urine of PXE patients, healthy carriers and normal subjects. METHODS: Using capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) we measured the amount of desmosines in the urine of 46 individuals (14 PXE patients, 17 healthy carriers and 15 controls) and in the plasma of 56 subjects (18 PXE patients, 23 healthy carriers and 15 controls). Pseudoxanthoma elasticum patients and carriers were identified by clinical, structural and molecular biology analyses. RESULTS: The urinary excretion of desmosines was two-fold higher in PXE patients than in controls (P < 0.01); the values for healthy carriers were intermediate between those of PXE patients and controls. A very similar trend between patients and their relatives was observed for plasma desmosines. There was a significant correlation between the amount of the desmosines in plasma and urine. Moreover, a positive correlation was observed between urinary desmosine content and age of the patients as well as between urinary desmosine content and severity of clinical manifestations. CONCLUSIONS: Both the urinary and plasma desmosine concentrations indicate that elastin degradation is higher in PXE patients and, to a lesser extent, in healthy carriers than in normal subjects. Data seem to indicate that the amount of elastin breakdown products correlates with the age of patients as well as with the severity of the disease.