Cytodiagnosis and protein typing of amyloid from a vitreous washing: initial diagnostic workup of hereditary amyloidosis.

Hereditary amyloidosis is a challenging but critical diagnosis, with serious implications with regard to treatment and disease surveillance for both patients and their families. Systemic symptomology is often vague. As vitreous amyloid deposition is strongly linked to the systemic, hereditary disease, its cytodiagnosis in the vitreous may be the incipient finding of hereditary amyloidosis. We describe a 64-year-old man with a history of heart disease and peripheral neuropathy who presented with asymmetric visual disturbances and vitreous opacities, leading to diagnostic vitrectomy. Amyloid was identified on a ThinPrep slide of the vitreous sample via Congo red stain. Creation of a cell block from the residual ThinPrep sample allowed for amyloid protein typing, identifying ATTR (transthyretin)-type amyloid and strongly suggesting hereditary amyloidosis. Subsequent sequencing of the patient's TTR gene identified a pathogenic variant that is associated with autosomal dominant hereditary transthyretin-mediated amyloidosis.