[The pathogenesis of herpetic keratitis]

Viral infections of Herpes origin are the most commonly encountered ones in man. The most important member of this family is the Herpes simplex virus (HSV), two varieties of which are known to exist: HSV-1 affects predominantly the upper half of the body, whereas HSV-2 is associated mainly with diseases of the urogenital tract. In the immunocompetent host, viral replication is usually confined to cutaneous and mucocutaneous sites, invasion of subcutaneous tissues being impeded by an early onset of non-specific defence mechanisms. These are rapidly complemented by the specific, mainly cellular, immune response.

Epithelial dendritic keratitis is the first symptomatic clinical finding, and after several recurrences, the corneal stroma may become involved. This condition of herpetic stromal keratitis (HSK), which, in contrast to the epithelial one, is believed to be directed by a predominantly immunopathological process, is one of the leading causes of infectious blindness in developed countries.

The mechanisms underlying HSK, and the establishment of viral latency and reactivation are poorly understood. But on the basis of studies with mice as well as clinical immunohistological observations, evidence is now accumulating in support of a cell-mediated mechanism being responsible for corneal destruction.

Our present knowledge of the pathogenesis of herpetic keratitis is incomplete. The different pathophysiological aspects reflecting our current understanding, such as that of a virally induced autoimmune disease, form the basis of accepted clinical treatment concepts.