ABSTRACT
Polymyalgia rheumatica (PMR) is a disease commonly seen in elderly individuals, however, the etiology has not been reported. Typical clinical features include bilateral shoulder pain and morning stiffness, while serologic autoantibody test findings are negative. Approximately 40%-50% of affected patients present with low-grade fever, fatigue, and appetite loss, which we often experience in the field of general medicine, and thus, the condition should not be given low priority. However, knowledge regarding such constitutional manifestations is also limited. We encountered an elderly woman with a fever of unknown origin that developed following a parathyroidectomy for a single parathyroid adenoma, after which severe shoulder pain and morning stiffness emerged, leading to a diagnosis of PMR. The fever developed several days prior to appearance of severe pain, which is an uncommon presentation in PMR cases. Our patient had low-grade inflammation without pyrexia prior to the surgery, which might have been an important reason for the accelerated immoderate immune activation leading to PMR induced by surgery in this case. Furthermore, she was infected with the influenza A virus 3 weeks before coming to us. Some reports have suggested a relationship between the influenza virus or vaccine and PMR. It is difficult to conclude regarding the definite trigger in our patient, though the details of this case should be helpful for a better understanding of the disease.
ABSTRACT
BACKGROUND AND AIMS: The enzyme xanthine oxidoreductase (XOR) catalyzes the formation of uric acid (UA) from hypoxanthine and xanthine, which in turn are products of purine metabolism starting from ribose-5-phosphate. Besides the synthesis of UA, basic research has suggested that XOR is involved in the regulation of reactive oxygen species, adipogenesis, and peroxisome proliferator-activated receptor-γ (PPAR-γ). XOR activity has shown to be much lower in humans than in rodents, which makes its accurate measurement difficult. Recently, a novel human plasma XOR activity assay has been established using a combination of liquid chromatography (LC) and triple quadrupole mass spectrometry (TQMS) to detect [13C2,15N2]UA using [13C2,15N2]xanthine as a substrate. Using this novel assay, we for the first time determine plasma XOR activity in humans, and evaluate its association with insulin resistance, high-sensitivity C-reactive protein (hsCRP) levels, and other parameters. METHODS: Of the 29 volunteers who wished to participate in the study, 3 were excluded; of the remaining, 11 were female and 15 were male with a mean age of 25.9±3.3years. Blood samples were collected under fasting conditions in the early morning to measure XOR activity and other parameters. RESULTS: The natural logarithmic value of XOR activity (ln-XOR) in plasma was 3.4±0.8pmol/h/mL. Ln-XOR had a positive correlation with UA and body mass index (BMI) and a negative correlation with quantitative insulin sensitivity check index (QUICKI) and adiponectin. In addition, ln-XOR had a positive correlation with hsCRP levels, which serves as a marker of chronic inflammation. CONCLUSIONS: The present study has shown that XOR activity is correlated with serum UA levels in humans. Furthermore, even in young subjects, XOR activity is correlated with insulin resistance, BMI, and subclinical inflammation. Thus, XOR activity may be potentially involved in adiposity and subclinical inflammation in humans.
