Clinical Reasoning: Multifocal neuropathies in a patient with Waldenstrom macroglobulinemia and prior borreliosis

A 77-year-old man presented with 1 week of back pain, night sweats, confusion, jaundice, and pruritus with patchy, blanchable erythematous lesions over his trunk (figure 1). Neurologic examination was normal, but a lumbar spine MRI showed diminished bone marrow signal. He was thrombocytopenic (13 × 10⁹/L) and anemic (7.2 g/dL) with an immunoglobulin M (IgM) kappa monoclonal gammopathy and bone marrow biopsy consistent with Waldenstrom macroglobulinemia (WM). He was initiated on 60 mg prednisone daily and rituximab. Skin biopsy revealed nonspecific dermal edema with perivascular inflammation. Two weeks into admission, he developed left lower motor neuron facial droop, and was kept on the prednisone started 2 days prior for his WM. Shortly after that, it was noted that his Borrelia burgdorferi enzyme immunoassay (EIA) screen and supplemental B burgdorferi IgM immunoblot were positive, while the immunoglobulin G immunoblot was negative. Three weeks later, his facial palsy had resolved, but given extensive tick exposure history, he was treated with 3 weeks of doxycycline. CSF collection was deferred due to thrombocytopenia.