MOOREN ULCER

pathogenesis although the etiology of puk is unknown, evidence is mounting that autoimmunity

plays a key role. the following have been found in patients with mooren

ulcer:

deficiency of suppressor t cells

increased level of iga

increased concentration of plasma cells and lymphocytes in the conjunctiva adjacent

to the ulcerated areas

increased cd4+/cd8+ and b7-2+/antigen-presenting cell ratios as well as increased

vcam - i, vla-4, and icam -i in the vascular endothelium of conjunctival vessels

tissue-fixed immunoglobulins and complement in the conjunctival epithelium and

peripheral cornea

A significant number of resident cells in Mooren ulcer specimens express MHC class II antigens,

a reflection of the degree of immune-mediated i nflarnmation in the tissue. It has been suggested

that auto reactivity to a cornea-specific antigen may playa role in the pathogenesis of th is

disorder, and humoral and cell -mediated immune mechanisms may be involved in the init iation

and perpetuation of corneal des truction. The proximity of the ulcerative lesion to the limbus

probably has pathophysiologic im portance (as discussed earlier in the sectio n on PUK), because

resection or recession of the limbal conjunctiva can often have a beneficial therapeutic effect.

Although the cause of Mooren ulcer is unknown, precipitati ng factors include accidental

trauma or surgery and exposure to parasitic infection. The latter is of considerable importance, as

th e incidence of Mooren ulcer is particularly high in areas where parasitic (eg. helmi nthic)

infections are endemic. The principal hypotheses are that inflammation associated with previous

injury or infection may alter the expression of corneal or conjunctival antigens (to which

autoantibodies are then produced) or that cross-reactivity occurs between the i.m rnune effectors

generated in response to infection and corneal autoantigens. The simultaneous presence of

multiple types of inflammatory cell s. adhesion. and co stimulatory molecules in Mooren ulcer

conjunctiva suggests that their interaction may contribute to a sustained immune activation as at

least part of the pathogenic mechanism of this disorder. By definition, Mooren ulcer is of

unknown cause. Cases of PUK due to known local (eg. rosacea) or systemic (eg. rheumatoid

arthrit is) diseases should not be called Mooren ulcer.

CLINICAL PRESENTATION Mom-en ulcer is a chronic, progressive, painful, idiopathic

ulceration of the peripheral corneal stroma and epithelium. Typicall y. the ulcer starts in the

periphery of the cornea and spreads circumfe rentially and then centripetall y. with a leading

underm ined edge of deepithelized tissue (Fig 7-19). A slower movement of ulceration proceeds

toward the sclera. The eye is inflamed and pain can be intense. with photophobia and tea ri ng.

Perforation may occur with minor t rauma or during secondary infection. Extensive

vascularization and fibrosis of the cornea may occur.

In some patients. it may be very diffi cult to di stinguish Mooren ulcer from idiopathic

PUK. An important distinguishi ng feature is the purely corneal involvement of Mom·en; PUK

has scleral involvement.

Two clinical types of Mom·en ulcer have been described. Unilateral Mooren ulcer

typically occu rs in an older patient population. Sex distribution is equal in this form, which is

slowly progressive. A second type of Mooren ulcer is more common in Africa. This form is

usually bilateral, rapidly progressive, and poorly responsive to medical or surgical intervention

(Fig 7-20). Corneal ulceration and perfo ration are frequ ent. Many of the patients with this form

of Mooren ulcer also have coexist ing parasitemia. It is possible that in this subgroup of West

African males, Mooren ulcer may be triggered by antigen- antibody reaction to helminthic toxins

or antigens deposited in the limbal cornea during the bloodborne phase of parasitic infection.

MANAGEMENT The multitude of therapeutic strategies used against Mooren ulcer un

derscores the relative lack of effec tive treatment. Topical corticosteroids, contact lenses,

acetyleysteine (Mucomyst 10%) and L-cysteine (0.2 molar), topical cyciosporine, limbal

conjunctival excision, and lamellar ke ratoplasty have all been described with variable success.

More recently, topical IFN-a" and topical cyclosporine 2%, as well as infliximab, have also been

reported as effective alternat ives. Systemic immunosuppressives such as oral corticosteroids,

cyclophosphamide, methotrexate, and cyclosporine have also shown promise in these cases.

Hepatit is C-associated cases of "Mooren ulcer" -type PUK have responded to in terferon

therapy.