Xeroderma pigmentosum is a genetic disorder characterized by extreme sensitivity to ultraviolet light.
Xeroderma pigmentosus is transmitted as an autosomal recessive character caused by defective repair of the damage to DNA induced by sunlight.
The earliest manifestations may consist of photophobia [fear of light] and a mild erythema on the checks which usually starts in infancy.
With advancing age, the patient develops hyperpigmented macular lesions somewhat resembling freckles, which first appear on the areas exposed to sunlight, but later these spread to the unexposed sites as well.
At any time, however, these are always most numerous on the exposed parts.
After a few years, a few small depigmented macules appearing in between the hyperpigmented macules can also be seen and the skin starts showing signs of atrophy as well as hypertrophy in several focalized areas.
In the later stages, the patient develops multiple malignant tumours which may consist of squamous cell epitheliomas, basal cell epitheliomas, malignant melanomas or even fibrosarcomas and this change usually leads to a fatal termination.
The rate of progression of the disease is quite variable; some patients live an almost normal life span, while others may terminate fatally even in childhood due to early malignancies.
Some patients have associated neurologic defects such as mental deficiency, areflexia, impaired speech and hearing, convulsions and microcephaly.
Ocular changes apart from photophobia may include ectropion, entropion, conjunctivitis, keratitis and ocular neoplasms.
In the early stages, the main treatment lies in protecting the individual from exposure to sunlights. this involves use of protective clothing and sunscreens. Malignancies must be excised as soon as possible.