An unusual neurological complication of light chain amyloidosis

Abstract

A 59-year-old female presented with acute renal failure, anaemia, immunoglobulin (Ig)G lambda paraproteinaemia, lytic bone lesions and bone marrow plasmacytosis (60%) with no evidence of amyloid deposition. Fluorescence in-situ hybridization analysis of marrow showed t(11;14)(q13;q32) and monosomy 13. Renal biopsy showed lambda light chain cast nephropathy consistent with myeloma kidney. She achieved less than a partial remission with autologous stem cell transplantation. A year later, she developed bilateral shoulder swelling with synovial thickening, and biopsy showed deposition of lambda light chain-derived amyloid. A repeat marrow biopsy confirmed myeloma-associated amyloid. In addition, a new symptom of tingling and numbness of hands and feet, initially perceived as AL amyloidosis-related small fibre neuropathy appeared. She had mild upper and lower extremity weakness and truncal numbness along with unilateral Babinski’s reflex, but no sensory level could be appreciated. She denied bladder or bowel incontinence. Magnetic resonance imaging of the cervical spine demonstrated cord compression by a tumour-like mass within the dorsal paraspinal soft tissues at the C2–3 level (left and middle panels). Surgical resection of the mass revealed an amyloidoma (right panel), and led to near complete resolution of her neurological symptoms. Subsequently, she received bortezomib-dexamethasone therapy with an excellent haematological response and stabilization of soft tissue findings. Her disease has been stable off-therapy for almost 11 months at the time of last follow-up. Myeloma-associated neurological manifestations can have diverse aetiologies. Peripheral neuropathy is not common at diagnosis in multiple myeloma (MM), and is usually related to concurrent amyloidosis or use of neurotoxic agents. Radiculopathy, on the other hand, is the most common neurological complication of MM, a result of nerve compression by paravertebral/extramedullary plasmacytoma, or infrequently, collapsed bone itself. Signs of spinal cord compression mandate urgent intervention. In our patient, compressive neuropathy resulted from a rare finding of a cervical amyloidoma. Such cases typically require prompt decompression with surgical resection of the mass to avert impending quadriparesis.