Muscular Sarcoidosis Detected by F-18 FDG PET/CT in a Hypercalcemic Patient
In November 2009, a 50-yr-old female was admitted to our hospital with idiopathic transient pulmonary edema. Her weight was 49 kg, creatinine clearance 33.8 mL/min and calcium 9.9 mg/dL. Her echocardiogram showed mild diastolic dysfunction with ejection fraction of 55%. Her pulmonary function was moderately restricted with 51% of forced vital capacity. Her pulmonary edema was rapidly improved with diuretics therapy. In August 2010, she was re-admitted with hypercalcemia. She had underlying diabetes for 20 yr. Her diabetes was complicated with proliferative retinopathy, chronic renal impairment, and a chronic foot ulcer. At the time of her recent admission, her weight was 37 kg and she appeared chronically ill and emaciated. She reported 2 weeks of general weakness. We could not find any abnormal mass or tenderness except generalized muscle atrophy at the beginning. Creatinine clearance was 19.4 mL/min, calcium 14.5 mg/dL, phosphate 5.0 mg/dL, and ionized calcium 1.78 mM/L. Her 24-hr urine calcium level was 186.2 mg/day, and intact parathyroid hormone (PTH) of 15.77 pg/mL. These ambiguous laboratory findings prompted further studies of non-parathyroid-related hypercalcemia. Her 25-hydroxy Vitamin D level was 21.3 ng/mL, 1,25-dihydroxy Vitamin D was 43.1 pg/mL (normal, 25.1-66.1), and parathyroid hormone related peptide (PTHrP) was under 1.1 pM/L. The thyroid hormone level, serum electrophoresis and tumor markers were normal. The angiotensin-converting enzyme (ACE) level was elevated to 353.1 IU/L (normal, 20-70), and muscle enzymes (CPK/LDH/AST) were normal. The chest radiograph, neck ultrasound, and whole body bone scan were unremarkable. F-18 FDG PET/CT was performed for the evaluation of possible hidden malignancy. The PET/CT showed increased uptake of small lymph nodes in the subcarina and both hila. In addition, multiple streaky and dotted muscular uptakes were noted along whole body including the back and extremities (). We reexamined her whole body and found a 2 cm-sized soft and non-tender mass in the left gastrocnemius muscle. Excisional biopsy was performed of the mass, and the microscopic finding demonstrated non-necrotizing granulomas with multinucleated giant cells and without acid-fast bacilli or fungi () consistent with muscular sarcoidosis. Imaging studies also revealed gallstones and bilateral renal stones, and we performed extracorporeal shock wave lithotripsy of the ureteral stone successfully. However, some renal stones remained.\nAcute severe hypercalcemia was relieved temporarily by hydration and furosemide. Prednisolone was started with 20 mg per day and then rapidly tapered to 5 mg per day within 1 week. The serum calcium level was normalized and maintained with prednisolone 5 mg a day, but ACE level continued to fluctuate. Her follow-up clinical data were laid out in the . Her glucose levels were controlled with insulin, and her weight increased to 50 kg with muscle gain. On follow-up PET/CT at one and half year later, muscular uptake was no longer seen. However, increased uptake in the mediastinal and hilar lymph nodes persisted ().