Mayo Clin Proc, February 2002, Vol 77 Residents’ Clinic 189 Mayo Clin Proc. 2002;77:189-192 189 © 2002 Mayo Foundation for Medical Education and Research Residents' Clinic 58-Year-Old Man With Fatigue and Flank Pain GRACE KHO DY, MD,* AND ELAINE B. YORK, MD† * Resident in Internal Medicine, Mayo Graduate School of Medicine, Mayo Clinic, Rochester, Minn. † Adviser to resident and Consultant in Community Internal Medi- cine, Mayo Clinic, Rochester, Minn. See end of article for correct answers to questions. Address reprint requests and correspondence to Elaine B. York, MD, Division of Community Internal Medicine, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (e-mail: york.elaine@mayo.edu). A 58-year-old man presented to our institution because of a 2-week history of fatigue, malaise, and lower extremity myalgias associated with bilateral flank pain and passage of sandy material on micturition. He denied having fever, hematuria, nausea, vomiting, or weight loss. The patient’s medical history was notable for recurrent nephrolithiasis for which hydrochlorothiazide was pre- scribed and psoriasis, which was well controlled with Goeckerman treatment. Surgical history included nasal polypectomy and orchiopexy for cryptorchidism. The patient’s vital signs on admission included a tem- perature of 37.4°C, regular heart rate of 78 beats/min, and blood pressure of 153/83 mm Hg. Physical examination findings were unremarkable except for multiple scaly plaques distributed primarily on the extensor surfaces of his knees and elbows, consistent with psoriasis. He had no palpable lymphadenopathy or hepatosplenomegaly. The initial complete blood cell count showed a hemoglobin level of 11.9 g/dL (reference range shown parentheti- cally) (13.5-17.5 g/dL), hematocrit of 33.6% (38.8%- 50%), mean corpuscular volume of 89.2 fL (81.2-95 fL), leukocyte count of 6.9 × 10 9 /L (3.5-10.5 × 10 9 /L), and platelet count of 266 × 10 9 /L (150-450 × 10 9 /L). Labora- tory studies yielded the following: sodium, 136 mEq/L (135-145 mEq/L); potassium, 4.3 mEq/L (3.6-4.8 mEq/ L); calcium, 12.5 mg/dL (8.9-10.1 mg/dL); magnesium, 1.5 mg/dL (1.7-2.1 mg/dL); creatinine, 4.6 mg/dL (0.8- 1.2 mg/dL); serum urea nitrogen, 42 mg/dL (6-21 mg/ dL); chloride, 96 mEq/L (100-108 mEq/L); bicarbonate, 29 mEq/L (22-29 mEq/L); phosphorus, 3.7 mg/dL (2.5- 4.5 mg/dL); and serum pH, 7.46 (7.35-7.45). Urinalysis revealed a pH of 6.5 and a trace of proteinuria; micro- scopic examination showed 1 to 3 red blood cells per high-power field. Findings on chest radiography were normal except for minimal anterior wedging of 1 mid- thoracic vertebral body. The patient was admitted to the hospital for management of hypercalcemia. 1. Which one of the following is the most likely cause of hypercalcemia in this patient? a. Primary hyperparathyroidism b. Hydrochlorothiazide intake c. Hyperthyroidism d. Multiple myeloma (MM) e. Familial hypocalciuric hypercalcemia (FHH) The degree of hypercalcemia may be useful diagnosti- cally. Primary hyperparathyroidism is often associated with borderline or mild hypercalcemia, with the serum calcium concentration often being lower than 11 mg/dL. 1 Anemia is not typically present, although it may occur occasionally due to replacement of the marrow with fibro- sis. These features do not fit our patient’s clinical situation. In a patient taking hydrochlorothiazide, thiazide-in- duced hypercalcemia is usually mild. Thus, thiazide intake per se is rarely the primary cause of a serum calcium level higher than 12 mg/dL. Our patient’s calcium level suggests the presence of an underlying disease even if the diagnosis is not suspected before initiation of thiazide. 2 Fatigue and malaise may be the initial manifestations of an apathetic form of hyperthyroidism that is found espe- cially in elderly patients. Hyperthyroidism can produce mild hypercalcemia, which is found in one fourth of pa- tients with hyperthyroidism. However, blood calcium lev- els seldom exceed 11 mg/dL. 3 In addition, renal calculi are distinctly uncommon in a patient with thyrotoxicosis. 4 Hypercalcemia occurs in about 30% of all patients with MM. Diffuse bone loss and vertebral fractures occur in most patients. The serum creatinine value is elevated in more than one half of patients at diagnosis and is higher than 2.0 mg/dL in approximately one fourth of patients. A normocytic, normochromic anemia is seen in nearly two thirds of patients at the time of diagnosis. The presence of mild anemia, hypercalcemia, acute renal failure, and verte- bral fracture in our patient suggests MM. Hypercalcemia that occurs in patients with FHH is usually mild. Mutations in the calcium-sensing receptor on the parathyroid cells and kidneys lead to a defective calcium regulation such that higher than normal calcium For personal use. Mass reproduce only with permission from Mayo Clinic Proceedings.