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Study clarifies genetic basis of rare form of corneal dystrophy
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PARIS — A study carried out in Spain confirmed the genetic basis and identified the specific gene mutation causative of punctiform and polychromatic pre-Descemet corneal dystrophy. The researchers also hypothesized the Spanish origin of this rare form of corneal dystrophy.
“After three other independent families presented to our clinic with this dystrophy, we set up a study to identify possible ophthalmic associations and to confirm and investigate the genetic basis of PPPDCD,” Jorge Alió del Barrio, MD, PhD, said at EuCornea 2019.
Punctiform and polychromatic pre-Descemet corneal dystrophy (PPPDCD) is a rare form of dystrophy, typically asymptomatic, characterized by the presence of punctiform, multicolored opacities/crystals in the posterior stroma, immediately anterior to the Descemet’s membrane. PPPDCD was previously reported in members of only 10 families.
“We found that affected individuals have stiffer corneas, with a significantly different corneal resistance factor and higher corneal hysteresis. As in previous studies, we did not find any systemic association with this disease,” Alió del Barrio said.
Genetic analysis proved that the disease has an autosomal dominant inheritance pattern with high penetration in all families. Two novel intronic variants were identified, PDZD8 and PRDX3, both within chromosome 10.
“These three families were from the same city, were supposed to be unrelated, but we proved with haplotype analysis that they had a common ancestor. A fourth family among those previously reported for PPPDCD was found by the same analysis to be unrelated. They had PRDX3 mutation but not the PDZD8. So, it is likely that PRDX3 is the causative gene for this type of dystrophy, which can now be reclassified with category 1 evidence as an independent entity rather than a subtype of pre-Descemet corneal dystrophy,” Alió del Barrio said.
Another interesting finding was related to the origin of all 13 families with reported PPPDCD. The majority of them were either located in Spain or had Spanish ancestors.
“We hypothesized that this specific mutation first appeared in Spain centuries ago and was then spread through Spain, Portugal and America. We could talk about a Spanish corneal dystrophy,” Alió del Barrio said. – by Michela Cimberle
Reference:
Alió del Barrio J, et al. Punctiform and polychromatic pre-Descemet corneal dystrophy: clinical evaluation and identification of the genetic basis. Presented at: EuCornea 2019; Sept. 12-13, 2019; Paris.
Disclosure: Alió reports no relevant financial disclosures.