History
The clinical findings in patients with PPMD are highly variable, with a broad clinical spectrum of findings, ranging from only occasional Descemet membrane vesicles to progressive debilitating corneal disease with corneal decompensation and glaucoma.
A family history of PPMD should be assessed.
Although most patients with PPMD are asymptomatic, the most common symptoms in those with more significant involvement are as follows:
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Photophobia
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Decreased visual acuity
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Foreign body sensation
Physical
The most characteristic finding on slit lamp biomicroscopy is multiple vesicles or blisters, either isolated or grouped in clusters, on the posterior corneal surface. The vesicles often have identifiable surrounding grayish halos. These are often at the level of Descemet membrane and the endothelium, but they can also be seen in the posterior stroma.
Slit lamp biomicroscopy may identify all or some of the following characteristics depending on the extent of the disease:
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Posterior corneal opacities occurring in linear bands or other polymorphous configurations with irregular scalloped edges [3]
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Areas of more diffuse posterior corneal opacities
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Focal excrescents of the Descemet membrane
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Iridocorneal adhesions
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Pupillary ectropion
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Corectopia
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Stromal and epithelial edema (advanced cases)
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Corneal guttae
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Iridocorneal adhesions (peripheral anterior synechiae)
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Increased intraocular pressure
Causes
The precise etiology of PPMD remains unknown. PPMD is a congenital inherited dystrophy involving abnormalities of the corneal endothelium and the Descemet membrane. [4, 5]
Most cases of PPMD are transmitted in an autosomal dominant fashion with variable expression, although autosomal recessive transmission has also been reported. [6]
A number of autosomal dominant cases of PPMD have been linked to a mutation in an unidentified gene located at band 20q11, whereas other cases have reported a mutation in a gene encoding for collagen VIII located on chromosome 1 (COL8A2) as the cause of PPMD.
In other cases, the genetic locus remains unknown.
PPMD has been associated with other conditions, including the following:
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Slit lamp image demonstrates posterior corneal vesicles and opacities in linear bands and other polymorphous configurations typical of posterior polymorphous corneal dystrophy.
