[Ratio of serum levels of 1,25-dihydroxyvitamin D3 and parathyroid hormone for the diagnosis and treatment of tuberculous peritonitis in a chronic kidney disease patient: a case report].

An 80-year-old man was admitted to our hospital because of exacerbation of preexisting chronic kidney disease (CKD). On admission, he showed elevated levels of serum creatinine (6.37 mg/dL) and corrected calcium (13.7 mg/dL). Although the serum levels of intact parathyroid hormone (I-PTH) and parathyroid hormone-related peptide(PTITH-rP)were low, the serum 1,25-dihydroxyvitamin D3 (1,25 (OH)2D3)levels were high. Computed tomography (CT) revealed ascites, and the ascitic fluid was exudative and serous with predominance of lymphocytes. The levels of adenosine deaminase (ADA) in the ascitic fluid were also elevated, and the results of QuantiFERON-TB2G (QFT-2G)assay were positive, indicating tuberculous peritonitits. Ascites resolved rapidly after initiation of the antituberculosis therapy. The elevated levels of serum calcium and 1,25 (OH) 2D3 returned to below-normal levels; however, serum i-PTH levels increased from 8.9 pg/ mL to 432 pg/mL. Diagnosis of extrapulmonary tuberculosis is often difficult in CKD patients. CKD patients show abnormal vitamin D activation, so these patients usually have low levels of serum 1,25(OH)2D3. On the other hand, in our patient, 1,25(OH)2D3 was extrarenally produced from tuberculous granuloma and therefore, he showed high levels of serum 1,25(OH)2D3 and correspondingly, low levels of serum i-PTH. We observed that the ratio of 1,25 (OH) 2D3:i-PTH decreased due to antituberculosis therapy. This ratio facilitated the diagnosis and evaluation of treatment for this condition.