Abstract
This study describes the case of an 84-year-old Japanese male who had been on maintenance hemodialysis for 3 years and was examined for gradually worsening hypercalcemia (corrected serum calcium level, 13.1 mg/dL). Although cultures of his sputum and gastric juice specimens did not show any evidence of Mycobacterium, positron emission tomography-computed tomography (CT) revealed lymphadenopathy in the pulmonary hila and mediastinum. A high value was also obtained during the QuantiFERON® TB-2G test (3.04 IU/mL). Moreover, the patient’s 1,25-dihydroxyvitamin D (1,25(OH)2D) to intact parathyroid hormone (i-PTH) serum level ratio was high (6.75 pg/pg). The patient was clinically diagnosed with hypercalcemia, which was suspected to have been caused by a tuberculosis infection, and was treated with antituberculous medications. After 6 months of therapy, his corrected serum calcium level had decreased to 8.7 mg/dL, and his 1,25(OH)2D to i-PTH serum level ratio had fallen to 0.04. A marked reduction in the size of the patient’s lymph nodes was observed on CT. The diagnosis of tuberculosis in cases involving atypical presentations such as extrapulmonary involvement is often difficult, and it may be necessary to start antituberculous therapy without a definite diagnosis in such cases. The low 1,25(OH)2D to i-PTH serum level ratios seen in hemodialysis patients are presumed to be due to a combination of disordered vitamin D metabolism and secondary hyperparathyroidism. In general, hemodialysis patients with granulomatous disease have higher serum levels of 1,25(OH)2D, which is synthesized in granulomas outside the kidneys, thereby leading to lower serum levels of i-PTH. In the present case, the patient’s high 1,25(OH)2D to i-PTH serum level ratio gradually decreased following the administration of antituberculous therapy. Thus, the 1,25(OH)2D to i-PTH serum level ratio aided the diagnosis of tuberculosis and the evaluation of the therapeutic response to antituberculous medication in a hemodialysis patient with hypercalcemia.
