Introduction

Hypercalcemia occurs about 10% of cancer patients overall. Parathyroid hormone related protein has been identified as the humorally secreted factor as a cause of hypercalcemia in malgnancies. In the current study, we describe a patient with PTH-rP secreting metastatic medulloblastoma who presented with humoral hypercalcemia of malignancy (HHM). To the best of our knowledge, this the first reported case of a PTH-rP secreting metastatic medulloblastoma.

Case Report

A 21-year-old-man was admitted to the hospital with complaints of fever, pain in the limb and lower back, fatigue and anorexia. In the medical history, he was operated 10 months ago because of medulloblastoma without insertion of a ventriculoperitoneal shunt. Radiotherapy of the entire craniospinal axis was performed. Since the operation, the patient had annual checkups by his primary physicians that included complete metabolic laboratory panel including serum calcium measurements.

On admission, physical examination revealed a cachectic man. He did not have lymphadenopathy and jaundice. The liver was just palpable below the right costal margin, without splenomegaly. Initial vital signs were a temperature of 38 0C, blood pressure of 130/70mmHg, heart rate of 114 beats/min, and respiratory rate of 26 breaths/min. The room oxygen saturation was 95%. Chest X-ray and ECG were unremarkable. Laboratory findings showed hypercalcemia, decreased levels of parathormone (PTH) and 25-hydroxycholecalciferol (25- vit D), liver dysfunction, and high C-reactive protein, sedimentation with normal levels of complete blood cell count and renal enzymes (table 1).

Figure 1

Urinary calcium level in 24 hours urine-output was 72.1 mg/24 hour (100-300). There were no localising clinical signs of infection. Cultures at the time of admission revealed no bacteria grew on the sputum, blood, or urine. Computerized tomography (CT) scan of the abdomen showed 2.5 cm cystic mass in right hepatic lobe. Brain CT was the same with previous CT (as 6 months ago). Bone scintigrahy displayed enhanced tracer uptake in both iliac bones, the proximal portions of both femurs. His fever did not decrease even with antipyretics and antibiotic. Ultrasonography guided liver biopsy was obtained, which revealed medulloblastoma metastasis. He received chemotherapy and radiotherapy and 4 mg zoledronic acid. His hypercalcemia was partially controlled by hydration, diuretic and zoledranic acid. The serum calcium, parathormone and 25-hydroxycholecalciferol levels returned to normal with the supressed serum parathormone-related-peptide (PTH-Rp) level after beginning therapy. In three and six months follow-up examinations, the patient was asymptomatic and his serum calcium levels were normal.

Discussion

Hypercalcemia is the commonest metabolic complication of malignancy, occurring in 10% of cancer patients overall. PTH-rP was identified as the humorally secreted factor which caused humoral hypercalcemia in malignancies (HHM) without coexisting hyperparathroidism (₁,₂). HHM is found in tumors of epithelial origin or hematologic malignancies. Hypercalcemia in most patients with cancer has predominantly a humoral basis rather than being caused by osteolysis due to tumor metastasis. Generally, PTH-rP has a multifunctional role in cancer, influencing the progression and development of bone metastasis as well as regulating cell growth and survival. Patients with persistently elevated PTH-rP associated HHM develop marked osteoclastic bone resorption, supression of osteoblastic bone formation and increased renal tubular reabsorption of calcium (₂). Loss of bone mineral density develops in patients with HHM. But in our patient it was not performed. Patients with malignancy have suppressed serum parathormone and supressed 25 hydroxycholecalciferol (₃,₄). We demonstrate the dramatic changes in serum calcium, phosphorus, parathormone and PTH-rP levels after therapy. To the best of our knowledge, this the first reported case of a PTH-rP secreting medulloblastoma in the literature. Our case highlights the importance of ruling out a PTH-rP secreting malignancy whenever hypecalcemiia accompanying a suppressed parathormone, vitamin D levels are encountered. If a patient is presented with hypercalcemia who has intracranial tumor must be investigated to demonstrate HHM, PTH-rP and metastasis.

Correspondence to

Mehmet KANBAY, MD, Baskent University Faculty of Medicine, Department of Internal Medicine, Ankara, TURKEY Address: 35. Sokak, No: 81/5, Bahcelievler, 06490, Ankara, TURKEY Tel: +90 312 2220398 Fax: +90 312 2130034 E-mail: drkanbay@yahoo.com