Mucous Membrane Pemphigoid (MMP) is a rare autoimmune disease (a group of diseases caused by the reaction of the person’s immune system producing antibodies - known as autoantibodies - which damage normally healthy body substances). These autoantibodies attack the skin and mucous membranes (the soft wet tissue lining the body openings including eyes, mouth, throat, genitals and back passage). When the eyes are affected it is called Ocular MMP (OMMP).
For many people with MMP, the eyes are the only site affected by the disease. About 60% of MMP patients have the disease in their eyes as well as other mucous membranes and/or their skin. In OMMP, the disease creates autoantibodies which damage the conjunctiva.
The conjunctiva is the thin mucous membrane which covers the eyeball and lines the inside of the eyelids. These autoantibodies cause conjunctivitis (a red inflamed conjunctiva) and scarring which often results in the eyelashes turning inwards and scratching the eye, making the problem worse. The original name for the disease was cicatricial pemphigoid; cicatricial means scarring. Both eyes are usually affected, although one eye is often worse than the other.
The disease progresses at different rates in different people, with rapid progression over weeks in a minority and slow progression over months or years in most. Early diagnosis in severe cases improves outcomes. With good treatment the effects of the disease can usually be controlled and both comfort and eyesight maintained.
We don’t clearly understand what causes OMMP. Although it is known to have a genetic element, it is not an inherited disease and we don't know what triggers the start of the disease. As with other autoimmune diseases, the immune system mistakenly attacks parts of the body. With MMP, your immune system creates autoantibodies which attack the layer immediately under the mucous membranes or skin, causing inflammation and scarring. Blistering is uncommon in the eyes but occurs at other sites. OMMP is not inherited, you can’t ‘catch’ it from someone else and it isn’t due to allergies or diet. It usually affects people over 40 (both men and women) but it has been diagnosed in younger adults and, rarely, in children.
In the eyes, the disease starts as conjunctivitis (red, painful and sticky eyes) which may be mild and intermittent or severe and persistent. These symptoms do not improve with treatment by antibiotics or eye drops and can create a lot of pain and irritation. Although scarring in the conjunctiva occurs early, it can be difficult to see with the naked eye until the disease is quite advanced.
As the inflammation and scarring progresses, it can also cause the pocket between the eyelids and eyeball (the conjunctival fornix) to reduce in depth, which may show as a droopy lid or as a smaller gap between the lids. The eyelids may turn in and the eyelashes may begin to scratch the surface of your eye. This is called trichiasis. The tear producing glands can also be affected by scarring and inflammation, causing the eyes to be dry.
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