A rare case of intramuscular orbital amyloidosis presenting as progressive esotropia in an adult.

Orbital amyloidosis is an uncommon entity. Lacrimal gland, orbital soft tissue and extraocular muscles are the usual sites of involvement. Deposition of amyloid in the extraocular muscle can be either isolated or associated with systemic amyloidosis. We describe a case of a 43-year-old male with isolated amyloid infiltration of the right lateral rectus muscle presenting as a progressive esotropia. The case was initially misdiagnosed as lateral rectus palsy and myositis due to non-specific radiological features of the entity. The diagnosis was confirmed by a biopsy. Intramuscular Botulinum toxin injection, was administered to the right medial rectus to alleviate diplopia temporarily, and strabismus surgery was planned at a later stage. Amyloid deposition is a rare cause of extraocular muscle enlargement. Histopathology is confirmatory. Screening for systemic amyloidosis is mandatory in all cases.