Severe Hypercalcemia Revealing Acute Lymphoblastic Leukemia: A Case Report.

Hypercalcemia is a rare metabolic disorder in children, with a wide range of potential etiologies, some of which can be life-threatening. We report the case of a 2.5-year-old male child admitted for progressive lower limb muscle weakness that began one month prior to admission, associated with abdominal pain and vomiting. Initial investigations revealed severe hypercalcemia at 21.2 mg/dL (5.28 mmol/L), accompanied by hypercalciuria, hypophosphatemia, and vitamin D deficiency. The patient was transferred to pediatric intensive care due to the onset of malignant hypercalcemia, altered consciousness, and ECG-documented arrhythmia. Treatment included aggressive intravenous hydration and administration of bisphosphonates, which partially corrected the calcium imbalance. An extensive etiological workup was conducted and revealed no endocrine, renal, or infectious abnormalities. A complete blood count showed microcytic hypochromic anemia without additional hematological anomalies, and the initial bone marrow aspirate was normal. Radiography of the forearm revealed demineralization of the distal metaphyses, while imaging of the tibia identified metaphyseal osteolytic lesions in the distal femur, proximal tibia, and fibula, with localized cortical lysis. Although the initial bone marrow aspirate was normal, the combination of osteolytic lesions and progressive skeletal demineralization was highly atypical for benign conditions and increasingly suggestive of an underlying malignant process. These imaging findings prompted repeat bone marrow evaluation, which ultimately confirmed B-cell acute lymphoblastic leukemia. Pancytopenia developed after the third bone marrow examination, which had confirmed the diagnosis, reflecting a rapid shift from the initially normal hematologic status. Chemotherapy was initiated promptly, and the patient responded favorably, with complete remission documented on follow-up marrow evaluation. This case underscores that hypercalcemia, whether isolated or accompanied by osteolytic lesions, may constitute the sole initial clinical manifestation of acute lymphoblastic leukemia (ALL) in children. The absence of circulating blasts, together with a completely normal initial bone marrow aspirate, demonstrates how ALL can present deceptively in its early stages. Recognizing that early marrow evaluations may be falsely reassuring is crucial in persistent or atypical presentations, highlighting the importance of repeating bone marrow assessment when clinical or imaging findings raise concern.