| Abstract |
Ophthalmic pterygium is a fibrovascular lesion of the corneoscleral junction, usually displaying progressive growth. It can threaten vision by extending to the central cornea. Pathogenesis remains unknown, although a relationship with environmental factors, such as solar light, has been established. Treatment is mainly surgical. The tendency to grow, the frequent postoperative recurrence as well as laboratory findings have led to the assumption that pterygium is a neoplastic condition. Furthermore, potentially oncogenic viruses, such as HPV and HSV have been detected in pterygia. Loss of Heterozygosity (LOH) implies the involvement of tumor-suppressor genes in pathological conditions. LOH can be detected with microsatellite DNA markers, amplified with polymerase chain reaction (PCR) in paired pathological and peripheral blood specimens. The present study investigated the incidence of LOH, in selected loci, as well as the presence of HPV and HSV in pterygia. Moreover, evaluation of the possible correlation of the findings with clinical and epidemiological information was carried out. Fifty pterygia and respective phenotypically normal conjunctival samples, together with peripheral blood samples were included. Samples were obtained from patients treated at the Ophthalmological Clinic of the University Hospital of Crete. A slit lamp examination was performed and an ophthalmological and medical history was recorded for each patient. PCR was employed to amplify 20 microsatellite markers located at regions 17p, 17q, 13q, 9p, 9q and 3p. HSV and HPV detection and typing were also performed with PCR. The highest incidence of LOH was observed at regions 9p (48% of specimens) and 17q (42% of specimens). No conjunctival specimen displayed LOH. HSV and HPV were detected in 22% and 24% of pterygium specimens respectively, while both HSV and HPV in 6% of specimens. No conjunctival specimen displayed HSV, while HPV was detected in 8%. All HSV-positive specimens displayed HSV-1, while all HPV-positive specimens displayed HPV-18. LOH at regions 9q31-33 and 3p22-21.3 was higher among patients living at higher altitudes and among those with a history of chronic conjunctivitis respectively. LOH incidence at region 9q31-33 was also higher among younger patients. Postoperative recurrence correlated with LOH at 9q and with the simultaneous presence of HPV and HSV. The detection of LOH at the examined loci, supports the concept that pterygium is a neoplastic condition and implies that it is genetically determined. The fact that the incidence of LOH at region 9q was higher among recurrent pterygia and correlated, especially at 9q31-33, with recognized risk factors such as young age and altitude of residence (which is related to exposure to ultraviolet irradiation), implies a possible prognostic value of LOH at this region for postoperative recurrence. Moreover, the correlation of the simultaneous presence of HPV and HSV with postoperative recurrence suggests that antiviral therapy in selected cases could play a role in the management of recurrent pterygia
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