The answer is skin deep: A case of intravascular large B cell lymphoma presenting as progressive paresis and bilateral abducens nerve palsy

The authors report a case of a 79-year-old, previously healthy, gentleman who presented with progressive proximal muscle weakness, petechial rash, weight loss, fatigue and diplopia. Neurologic exam demonstrated bilateral esotropia in the primary position and proximal muscle weakness in both upper and lower extremities bilaterally. Subsequent serum laboratory studies, cerebrospinal fluid analysis and neuroimaging failed to identify a unifying diagnosis. The patient was ultimately diagnosed with intravascular large B cell lymphoma (IVLBCL) via skin biopsy and subsequently underwent a single cycle of chemotherapy with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) before dying from respiratory failure. This case highlights the importance of entertaining a broad differential diagnosis for non-anatomical distribution of central nervous system (CNS) findings, especially when prior investigations into a structural cause have been unrevealing.