Editor,—Continuous renewal of the corneal epithelium is vital for the preservation of a smooth, transparent, refractile surface necessary for clear vision and ocular comfort. The regeneration of corneal epithelial cells takes place through centripetally migrating transient amplifying cells ultimately derived from stem cells located at the limbus.12 Deficiency of these progenitor cells leads to failure of epithelial cell regeneration and its replacement by invading conjunctival epithelium.3This pathological pathway is called limbal stem cell deficiency (LSCD) (see reviews Tseng4 and Tseng and Sun5). Corneal diseases with LSCD are characterised by conjunctival epithelial ingrowth, vascularisation, chronic inflammation, and fibrous ingrowth. Patients with LSCD often suffer from severe photophobia and profound loss of vision.

Cytotoxic agents such as 5-fluorouracil (FU) and mitomycin C are recognised causes of persistent epithelial defect and LSCD,6 when applied locally. Although a case of epithelial erosion arising from systemic cytotoxic therapy has been reported,7 little is currently understood about the pathophysiology of this effect. We were able to accurately correlate the clinical course of a patient with bilateral epithelial pathology arising from systemic hydroxyurea treatment with cytological and histological evidence of LSCD. We describe an unrecognised cause of both reversible and irreversible LSCD in these two eyes, respectively, and suggest that all cases of persistent corneal epithelial failure be investigated for limbal stem cell dysfunction.