P53 Expression in Pterygium Amongst Natives of High Versus Low Altitude

Purpose: To evaluate and compare the p53 gene expression in pterygia excised from natives of high and low altitudes. Methods: This prospective randomised interventional study, including 40 eyes (40 pterygia) of 40 patients, was conducted at our tertiary care institute for a period of 21 months. Patients admitted indoors were randomly selected for the study. Pterygium excision with conjunctival autografting was the standard procedure done. Pterygia and controls (normal conjunctiva) excised from both high (≥ 1500 m) and low altitude (< 1500 m) groups were analyzed immunohistochemically for p53 gene expression. Results: Overall, 29 (72.5%) pterygium specimens stained positive for p53 gene expression (p-value = 0.0001). 15 (75%) pterygia from high altitude (p-value = 0.0002) and 14 (70%) pterygia from low altitude group (p-value = 0.0003) stained p53 positive. Mean mutant p53 immunoreactivity was 31.03 ± 18.19%. However, the difference in incidence of p53 positivity (p-value = 1) or mean p53 immunoreactivity (p-value = 0.53) between the two study groups was not significant. All normal conjunctiva specimens stained p53 negative. Conclusions: Notwithstanding the difference in ultraviolet irradiation, the altitudinal variation in p53 gene expression in pterygium was found insignificant in our study. However, significantly high rate of mutant p53 positivity suggests pterygium to be a disorder of cell proliferation. Despite remaining unaffected by altitude, such alarmingly high incidence of p53 positivity warrants further randomised multicentric studies to rule out pterygium premalignancy and to investigate other possible mechanism(s) of p53 mutation in pterygium, besides those mediated by ultraviolet radiation.