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What Factors Influence Susceptibility to Ultraviolet Radiation?
Susceptibility to damage by UVR may be influenced by genetic and acquired disorders, genetic traits, age-related factors, and the use of some medications.
Genetic abnormalities can increase the susceptibility to UVR damage. These include disorders manifested in utero that may be lifelong or that may appear shortly after birth. Among them are disorders of keratinization and pigmentation. Several inherited disorders in which there is marked susceptibility to UVR in early childhood include xeroderma pigmentosum, Bloom's syndrome, Rothmund-Thomson syndrome, the porphyrias, phenylketonuria, dysplastic nevus syndrome, and the basal cell nevus syndrome.
There are also numerous and diverse acquired diseases that manifest increased light susceptibility. Examples include persistent light reaction, actinic reticuloid, polymorphous light eruption, solar urticaria, hydroa aestivale, hydroa vacciniforme, actinic prurigo, lupus erythematosus, dermatomyositis, Darier's disease, and disseminated superficial actinic parakeratosis.
Significant factors that influence susceptibility to UVR damage include race, ethnicity, eye and hair color, and the tendency toward formation of freckles and nevi. One approach to categorizing humans in terms of susceptibility to UVR is typing according to history of sunburning and tanning. Six skin types have been defined. Type I individuals always burn and never tan; type VI individuals always tan and never burn. The age of an individual may be correlated with factors that influence the susceptibility to UVR. These may include age-related structural differences in the skin, behavioral differences (e.g., adolescent risk taking) and, hypothetically, age-related immunological differences.
Numerous systemic medications may augment UVR susceptibility. Increased UVR damage may occur with the use of oral antibiotics, antihypertensives, psoralens, immunosuppressive agents, nonsteroidal anti-inflammatory drugs, and numerous other agents. In addition, a number of topical medications and industrial chemicals may increase the susceptibility to damage by sunlight. These include topical psoralens, tretinoin, and other photosensitizing and depigmenting agents.
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