[Severe Vitamin D(dihydrotachysterol)-intoxication with temporary anemia and hypercalcemia responsive to...

Severe Vitamin D(dihydrotachysterol)-intoxication with temporary anemia and hypercalcemia responsive to bisphosphonates. HISTORY AND FINDINGS: A 31-year old female patient presented with pain of her skeletal system. 6 months prior to her presentation, she underwent thyroid surgery for Graves disease. She also suffered from endocrine orbitopathy. Afterwards, she expirienced surgical hypoparathyroidism and received dihydrotachy-sterol (A.T.10 (R)) in a dose of up to 4 mg per day. The physical examination was unremarkable except for the presence of Graves' ophthalmopathy and a swelling at the left ancle. INVESTIGATIONS: Upon admittance, she had severe hypercalcemia (serum calcium: 4.1 mmol/l) with plasma intact PTH levels below the limit of detection, renal failure (serum creatinine: 5.5 mg/dl) and normocytic anemia (initial hemoglobin: 8.3 g/dl, upon rehydration: 6.6 g/dl). TREATMENT AND COURSE: Upon rehydration and induced diuresis, the renal function improved and the serum calcium came down rapidly in the early treatment phase. However, serum calcium remained elevated at around 3.0 mmol/l after 4 weeks. Only after the use of the bisphosphonate pamidronate (15 mg), serum calcium returned into the normal range and remained there. Treatment for hypoparathyroidism had to be reinstituted only 20 weeks after dihydrotachysterol had been discontinued. The anemia had resolved without any treatment at that time. CONCLUSIONS: Treatment with dihydrotachysterol and other long-acting Vitamin D preparations has to be monitored closely because of the risk of severe hypercalcemia, which may be difficult to treat. In our case, dihydrotachysterol was still active until week 20 after the drug was discontinued. Anemia should be considered as a side effect of dihydrotachysterol intoxication and does not warrant elaborate differential diagnosis in this context. A single administration of a bisphosphonate turned out to be of major therapeutic benefit and resulted in a lasting correction of hypercalcemia. Therefore, bisphosphonates should become part of the treatment regimen for vitamin D intoxication.