Diplopia as the initial symptom of multiple myeloma in a patient with sarcoidosis.

We present the case of a 45-year-old man with a known history of sarcoidosis who presented with double vision and headache. On examination, he was found to have left abducens and hypoglossal nerve palsy. CT and then MRI demonstrated extensive osseous lesions with a large expansile mass involving the clivus bone and sphenoid sinus. Laboratory data were remarkable for normocytic anaemia, low anion gap and elevated total protein which raised the suspicion for multiple myeloma. Subsequent protein electrophoresis and immunofixation illustrated monoclonal spike of IgG lambda present in the gamma zone. This was followed by a bone marrow biopsy that demonstrated plasma cells compromising around 80% of marrow cellularity. Left sphenoidal mass biopsy was consistent with plasmacytoma. Based on these findings, the patient was initially started on palliative radiation to shrink the intracranial tumour and is currently undergoing induction chemotherapy. © BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.