Nonsecretory Multiple Myeloma – a diagnostic challenge!

The Nonsecretory Multiple Myeloma is a rare variant (1-5 %) of the classical form of multiple myeloma (MM). Although clinically similar to MM, nonsecretory multiple myeloma is not associated with a monoclonal gammopathy in serum or urine, making it difficult diagnosis this entity. The authors describe the case of an eighty-year-old man, who was admitted in September 2012 in our hospital, by acute renal failure, low back pain and disorientation. He had been well until approximately 6 months earlier, when he experienced adynamia, asthenia and weight loss (8kg). On examination, he showed no significant alterations except urinary retention requiring catheterization. The analytical study performed pointed out normocytic normochromic anemia (Hb 9.9 g/dl), renal failure and increase of B2 microglobulin (11684). The electrophoresis of serum proteins was normal, as well as urinary light chains and serum. Renal ultrasound was normal. Thoracic-abdominal-pelvic computed tomography (CT) revealed multiple osteolytic metastases, associated to a mass of soft tissue, in pelvis bones and in several vertebral bodies. Following the study of an occult primary tumor, upper and lower endoscopy, bronchofibroscopy with bronchoalveolar lavage, prostate and thyroid ultrasound were performed and showed no changes. The magnetic resonance imaging of the spine revealed multiple infiltrative lesions of the cervical-dorsal-lumbar-sacred vertebrae, pathological fractures of the vertebral bodies of D4, D7 and D9 and a mass of soft tissue/infiltrative component in D12. It also displayed secondary infiltrative lesions of iliac bones and some ribs. The positron emission tomography (PET) showed avidity for 18FDG in iliac and sternal body. The patient underwent CT-guided aspiration biopsy of iliac lesion, which result was negative for neoplastic involvement. This result led to the completion of two additional biopsies directed at D12, both inconclusive. It was instituted systemic corticosteroid therapy and fluid therapy with good clinical outcome, which allowed the patient’s discharge to the outpatients’ department. Five months later, he was re-admitted for low back pain, decreased strength in the lower limbs, worsening of renal function and hypercalcemia. He made a new thoracic-abdominal-pelvic CT scan, which revealed progression of lytic lesions, affecting all bone parts and increasing bone mass on D12, conditioning extensive lysis of the vertebral bodies. Given the exuberance of the lesion on D12 and the consequent damage to adjacent structures, an open biopsy was held and radiotherapy for symptomatic control was initiated. The histological result of the biopsy revealed plasmacytoma/multiple myeloma with restriction of kappa light chains. The patient was referred to the Oncology Service, and started dexamethasone in high doses. The bone biopsy showed 49% of plasmocytes, all with abnormal phenotypic characteristics. The nonsecretory multiple myeloma is an uncommon entity, with clinical presentation similar to MM, which diagnosis requires histological evidence of plasmocytic infiltration. Limitations inherent to biopsy may delay correct treatment. However, whenever we are faced with an elderly with bone pain, acute renal failure and anemia of unknown etiology, one need to persist in the diagnosis of MM, not forgetting this rare entity that is nonsecretory multiple myeloma