Pachymeningeal thickening and subdural effusion in POEMS syndrome

A 61-year-old man had an 8-month history of rapidly progressive sensorimotor neuropathy. On examination, there was lower limb oedema, hepatomegaly and lymphadenopathy. Nerve conduction studies showed marked slowing of conduction velocities in the upper limbs and absent sensory and motor responses in the lower limbs. Needle electromyography indicated severe axonal loss. Cerebrospinal fluid analysis showed 0.3 cells/µL (≤5) and elevated protein at 1.67 g/L (0.15–0.45). Serum immunofixation identified an IgA lambda monoclonal protein. Additional findings included hypogonadism, thrombocytosis (platelet count 494×10 9/L (150–400)) and thoracic vertebral lesions on CT imaging, fulfilling the diagnostic criteria for POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal band and skin changes) syndrome. MR scan of the brain, performed 6 months after the lumbar puncture and before starting treatment, showed diffuse pachymeningeal thickening with an asymptomatic subdural effusion (figure 1).