Keratitis may be caused by either congenital or acquired syphilis, although most cases are associated with congenital syphilis. Manifestations of congenital syphilis that occur early in life (within the first 2 years) are infectious. However, IK is a later, immune-mediated manifestation of congenital syphilis. Affected children typically show no evidence of corneal disease in their first years; stromal keratitis lasting for several weeks develops late in the first decade of life (or even later). These patients may also have nonocular signs of congenital syphilis:
dental deformities: notched incisors and mulberry molars
bone and cartilage abnormalities: saddle nose, palatal perforation, saber shins, and frontal bossing
cranial nerve VIII (vestibulocochlear) deafness
rhagades (circumoral radiating scars)
Widely spaced, peg-shaped teeth; eighth nerve deafness; and interstitial keratitis constitute the Hutchinson triad. Congenital syphilitic keratitis is bilateral in 80% of cases, although both eyes may not be affected simultaneously or to the same degree. Initial symptoms are pain, tearing, photophobia, and perilimbal injection. The inflammation may last for weeks if left untreated. Sectoral superior stromal inflammation and keratic precipitates are typically seen early in the disease course. As the disease progresses, deep stromal neovascularization develops. Eventually, the inflammation spreads centrally, and corneal opacification and edema may develop. In some cases, the deep corneal vascularization becomes so intense that the cornea appears pink—hence the term salmon patch (Fig 11-16). Sequelae of stromal keratitis include corneal scarring, corneal thinning, and ghost vessels in the deep layers of the stroma. Vision may be reduced because of irregular astigmatism and stromal opacification.
Stromal keratitis develops only rarely in acquired (as opposed to congenital) syphilis and, if it does, is unilateral in 60% of cases. The ocular findings are similar to those seen in congenital syphilitic keratitis. In general, uveitis and retinitis are much more common manifestations of acquired syphilis than keratitis.
Figure 11-16 Active syphilitic interstitial keratitis with salmon patch.
LABORATORY EVALUATION AND MANAGEMENT
A diagnosis of congenital syphilis is confirmed by identification of Treponema pallidum by dark-field microscopy or fluorescent antibody. The detection of specific IgM is currently the most sensitive serologic method. During the acute phase, ocular inflammation should be treated with cycloplegic drugs and topical corticosteroids to limit stromal inflammation and late scarring. The corneal disease can be suppressed with topical corticosteroids. If untreated, the disease can “burn out” over time; because it can lead to severe corneal opacification, earlier treatment can be beneficial in preventing ophthalmic sequelae. Patients with findings of IK should have a workup for syphilis. Systemic syphilis (or neuroretinal manifestations) should be treated with penicillin or an appropriate alternative antibiotic in accordance with the protocol for either congenital or acquired syphilis. The necessity of lumbar puncture in syphilitic IK is uncertain, and any patient with suspected syphilis should be referred for immediate consultation with a specialist in infectious diseases.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.