Hypercalcaemia, Renal Dysfunction, Anaemia, Bone Disease (CRAB Criteria): A Case of Lymphoma

Calcium elevation, Renal dysfunction, Anaemia and Bone disease (CRAB criteria) are usually seen in multiple myeloma (MM). We report a unique case of lymphoma with all the features of CRAB criteria. We describe a 59-year-old patient who presented with confusion, severe back pain, fatigue and constipation and was found to have hypercalcaemia, kidney dysfunction, anaemia and multiple osteolytic lesions. Physical examination and imaging did not reveal any enlarged lymph nodes. Work-up for MM (serum protein electrophoresis, serum immunofixation, bone marrow biopsy) was negative. The patient was diagnosed with diffuse large B-cell lymphoma based on a pelvic mass biopsy. Hence, our case report suggests that CRAB criteria are not pathognomonic of MM and that in the appropriate clinical scenario, lymphoma is a possible diagnosis. LEARNING POINTS: The CRAB criteria consist of end-organ damage with hypercalcaemia, renal dysfunction, anaemia and bone involvement. The CRAB criteria are not pathognomonic of multiple myeloma, and in the appropriate clinical scenario, lymphoma is a possible diagnosis. Major mechanisms by which hypercalcaemia of malignancy can occur are tumour secretion of parathyroid hormone-related protein (PTHrP), osteolytic metastases with local release of cytokines, or tumour production of 1,25-dihydroxyvitamin D (calcitriol).