Hypercalcemia due to endogenous overproduction of active vitamin D in identical twins with cat-scratch disease

Context.-The extrarenal synthesis of active Vitamin D sterols has a central causative role in the hypercalcemia associated with various granulomatous diseases. Objective.-To study the calcium metabolism in patients with cat-scratch disease who have hypercalcemia. Design.-Case report. Setting.-University hospital in Barcelona, Spain. Patients.-Two identical twins who developed asymptomatic hypercalcemia during the acute phase of cat-scratch disease. Main Outcome Measures.-Serial measures of calcium homeostasis and metabolism over a 2-month period. Results.-On admission and 6 and 7 days later, bath patients were found to have increased levels of serum and urinary calcium serum phosphate, and serum 1,25-dihydroxyvitamin D [1,25(OH)(2)D], whereas they had normal values of serum 25-hydroxyvitamin D and urinary cyclic adenosine monophosphate and decreased serum concentrations of intact parathyroid hormone. Sixteen and 20 days after admission, these abnormalities had resolved without treatment. A direct correlation was observed between the serum 1,25(OH)(2)D levels and both the serum and 24-hour urinary calcium concentrations. Also, the concentrations of calcium and 1,25(OH)(2)D paralleled the clinical activity of the infectious disease over the period these parameters were measured. Conclusions.-Our cases provide evidence that cat-scratch disease can produce hypercalcemia through the unregulated production of the metabolite 1,25(OH)(2)D. Cat-scratch disease should be added to the list of granuloma-forming diseases that are responsible for 1,25(OH)(2)D-mediated hypercalcemia.