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Editor,—Infectious crystalline keratopathy (ICK) is a condition in which there is a chronic and insidious non-inflammatory bacterial infiltration of the cornea. It is thought to have the distinct appearance of snowflake-like branching crystals on slit-lamp examination. We present a case of ICK occurring in a corneal graft which presented with the signs of graft rejection. ICK was not suspected clinically, but was diagnosed by histological examination of the failed graft.
A fit 90-year-old woman underwent uneventful left extracapsular cataract extraction, posterior chamber lens (PMMA) implantation, and penetrating keratoplasty using an organ cultured cornea, for bullous keratopathy secondary to Fuchs’ endothelial dystrophy.
Postoperatively, prednisolone eyedrops 1%, 2 hourly and chloramphenicol eyedrops were administered. A large epithelial defect had disappeared by day 5, when she was discharged home. At 1 month there was diffuse superficial punctate erosions on the graft epithelium and an excessive number of unexplained stromal folds persisted. Treatment was changed to preservative free prednisolone 0.5% eyedrops and chloramphenicol eyedrops. In the eighth week the graft stroma remained thickened and extensive fine and one large endothelial keratic precipitates (KPs) appeared over a few days (Fig 1). The corneal epithelium was intact, no stromal infiltrate was present, and the anterior chamber was quiet. Intraocular pressure was normal. A diagnosis of acute graft rejection was made and the patient was treated with hourly prednisolone 1% eyedrops. The KPs disappeared slowly but stromal oedema persisted. During hospitalisation a transient epithelial defect appeared in the graft. Because of persistent corneal oedema and poor vision, the patient underwent repeat left penetrating keratoplasty 5 months after her original operation.
Histological examination of the recipient’s corneal disc confirmed Fuchs’ endothelial dystrophy, with no evidence of inflammation or infection. The failed corneal graft showed epithelial oedema and central thinning, and discontinuities were evident in Bowman’s layer. A few neutrophil polymorphs permeated the deeper corneal fibres but at the periphery there were abundant Gram positive cocci (Fig 2). There was moderate endothelial cell loss. Adherent to the posterior corneal surface were numerous collections of histiocytes including pigment containing macrophages (Fig 2). Based on these appearances the diagnosis of bacterial infection causing crystalline keratopathy was made.
Infectious crystalline keratopathy was first recognised in the mid 1980s.1-3 It is a non-inflammatory bacterial colonisation which has been described in corneal transplants1-3 and in corneas previously affected by herpes simplex orAcanthamoeba.4 ICK is associated with the prolonged use of topical steroids23 and it has the characteristic appearance of multifocal, white, branching, crystalline, needle-like, progressive stromal opacities associated with little inflammation.1 Light microscopy shows intrastromal pockets of bacteria, usually Gram positive cocci, with minimal inflammatory infiltrate. Streptococcus viridans (α haemolytic) is the commonest organism to be isolated5 but culture is often unsuccessful and specific culture conditions may be required.6 The conjunctival flora has been implicated as the source of bacteria. Possible routes of bacterial entry include persistent epithelial defects,23 migration along suture tracks,17 and compromised epithelium due to herpetic keratitis.2
In our patient, although an intermittent epithelial defect occurred, the stromal oedema, absence of stromal infiltrate, and presence of extensive KPs on the donor endothelium suggested graft rejection rather than microbial keratitis. However, histopathology revealed the KPs to be macrophages (not lymphocytes) and intralamellar Gram positive bacteria were noted, typical of ICK. We presume the persistent stromal oedema was secondary to endothelial dysfunction and intralamellar bacterial infiltration, despite a reasonable complement of endothelial cells. We are not aware of other descriptions of ICK masquerading as graft rejection.
Early recognition and suspicion of ICK is important. Management consists of reduction and withdrawal of topical steroids and prolonged intensive treatment with topical antibiotics.5 The response to antimicrobial treatment may be poor, possibly because of poor intralamellar penetration or drug resistance. Despite the treatments described, the consequence may be graft failure requiring repeat penetrating keratoplasty.135
This case of ICK masquerading as graft rejection highlights the diversity of presentation of ICK. It should be at least considered in cases of suspected graft rejection, particularly if there are atypical features.