Fuchs' Superficial Marginal Keratitis
Fuchs’ superficial marginal keratitis (FSMK) is a rare inflammatory disease of the peripheral cornea in which recurrent infiltration causes progressive peripheral corneal thinning. It was initially described by Ferdinand Von Arlt in 1881, but is named eponymously for Ernst Fuchs who described the condition in greater detail in 1895. It is most common in young or middle-aged adults, although cases in older patients have also been reported.
The underlying cause of FSMK is unknown. Evaluation for autoimmune or other inflammatory systemic disease is often unrevealing. One case of FSMK in association with a perinuclear antineutrophil cytoplasmic antibody (p-ANCA)–positive vasculitis (demonstrated on skin biopsy) has been reported.
Due to overlapping clinical features and reported rare co-occurrence, it has been suggested that Terrien’s marginal degeneration and FSMK may be different manifestations of the same pathological process.
Patients may provide a history of recurrent episodes of eye redness which are commonly accompanied by pain or discomfort. Duration of episodes is generally on the order of days, but can be longer. Episodes may be self-limited.
FSMK characteristically presents with bilateral (often asymmetric) peripheral corneal stromal infiltration which causes thinning. (Figure 1) The area of thinning may be well-demarcated by a grey linear band. Corneal thinning may be severe and cause a descemetocele or spontaneous perforation, although this is not usually observed. Pseudopterygia characteristically form over areas of peripheral thinning. Peripheral hydropic cysts with Descemet membrane breaks may also form. The absence of lipid deposition in the vicinity of thinning, which is characteristic of Terrien’s, distinguishes FSMK from Terrien’s marginal degeneration.
Multimodal imaging may be helpful to demonstrate characteristic findings. Corneal topography/tomography can demonstrate irregular corneal astigmatism and peripheral thinning. Anterior segment optical coherence tomography (Figure 2) may be useful for assessing the extent of peripheral corneal thinning, especially when there is concern for evolving descemetocele.
There is no specific laboratory test to diagnose FSMK. However, laboratory testing may be utilized to exclude alternate diagnoses (such as PUK) or to assess for possible underlying systemic inflammatory etiologies.
- Furrow degeneration (senile furrow degeneration)
- Infectious keratitis
- Marginal keratitis (staphylococcal marginal keratitis)
- Mooren's ulcer
- Ocular surface squamous neoplasia
- Peripheral ulcerative keratitis
- Terrien's marginal degeneration
Owing to the rarity of FSMK, an optimal medical strategy is not known, and there is very limited data regarding the relative efficacy of various interventions. In fact, in most reported cases, disease progression occurs in spite of medical therapy. Topical steroids may be utilized to quell inflammation in acute episodes. Topical lubricants and antibiotics are also commonly utilized acutely. Systemic use of doxycycline (to modulate matrix metalloproteinase activity) and Vitamin C (to promote collagen synthesis) might be beneficial in either acute episodes or chronic/maintenance therapy, but data regarding such use are limited.
Cyanoacrylate glue may be utilized for spontaneous micro-perforations. Excision of pseudopterygia (as for excisional biopsy and/or ocular surface reconstruction) should not be routinely performed as iatrogenic perforation of severely thinned underlying stroma may occur. For example, if a pseudopterygium of FSMK is mistaken for a true pterygium and underlying thinning is not recognized, then an iatrogenic perforation may be more likely. However, Kotecha et al report a case in which superficial keratectomy with conjunctival autograft was utilized bilaterally and appeared to reduce disease activity. Amniotic membrane grafting may also be considered. If ocular surface reconstruction is to be pursued, superficial keratectomy should be performed cautiously to minimize risk of perforation.
For cases of spontaneous descemetocele or imminent perforation, marginal reconstruction with tectonic lamellar corneoscleral patch graft may be used. In diffuse severe thinning, 270 degree and 360 degree grafts have been utilized. FSMK may re-occur after grafting.
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