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, both patients were found to have increased levels of serum and urinary calcium, serum phosphate, and serum 1,25-dihydroxyvitamin D 1,25(OH)₂D], 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)₂D levels and both the serum and 24-hour urinary calcium concentrations. Also, the concentrations of calcium and 1,25(OH)₂D 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)₂D. Cat-scratch disease should be added to the list of granuloma-forming diseases that are responsible for 1,25(OH)₂D-mediated hypercalcemia.