A rare cause of diplopia: Solitary extramedullary plasmacytoma of the skull base.

Diplopia is a common presenting complaint with a broad spectrum of differential diagnoses. Causative pathologies may affect the eye, extraocular muscles, neuromuscular junction, cranial nerves and central nervous system. Tumours, inflammatory and autoimmune conditions, vasculopathies and atypical infections are the most common underlying pathologies. Solitary extramedullary plasmacytoma is a rare cause of diplopia. This case emphasises the importance of submucosal biopsies for diagnosis and early involvement of the multidisciplinary team. Moreover, we advocate a low threshold for a second opinion and further immunohistochemistry, particularly when there is diagnostic uncertainty with histological discordance.