Fuchs' endothelial dystrophy follows a pathogenetic sequence. Which of the following correctly describes the earliest histopathological change?

• A Loss of endothelial cell density below 1000 cells/mm²
• B Stromal oedema with epithelial bullae
• C Accumulation of abnormal collagen in Descemet's membrane (guttae formation) ✓
• D Subepithelial fibrous pannus formation

Explanation

The earliest change in Fuchs' endothelial dystrophy is the formation of guttae — focal excrescences of abnormal collagenous material deposited on the posterior surface of Descemet's membrane by dysfunctional endothelial cells. This begins centrally (central guttae) and progresses peripherally (cornea guttata). Only later do endothelial cell counts fall below the functional threshold, leading to pump failure, stromal oedema (corneal decompensation), and finally epithelial bullae (bullous keratopathy). SLC4A11 mutations are associated with early-onset Fuchs' dystrophy, while TCF4 repeat expansions are linked to the common late-onset form.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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