OBJECTIVES: I. Compare the safety and efficacy of T4N5 liposome lotion vs. a placebo lotion in reducing the incidence of actinic keratoses and protecting against other ultraviolet skin damage in patients with xeroderma pigmentosum.

OUTLINE: Randomized, double-blind study. Groups of 6 patients are randomly assigned in a 2:1 ratio to Arms I and II, respectively. Arm I: Chemoprevention. Lotion composed of T4 endonuclease V protein encapsulated in liposomes and suspended in phosphate-buffered saline in a hydrogel base, T4N5 Liposome Lotion, T4N5. Arm II: Control. Liposomes suspended in phosphate-buffered saline in a hydrogel base, Placebo, PLCB.

PROJECTED ACCRUAL: 6-30 patients will be entered in this multicenter study.

DISEASE CHARACTERISTICS: Diagnosis of xeroderma pigmentosum confirmed by unscheduled DNA synthesis assay At least one histologically confirmed actinic keratosis All actinic keratoses removed prior to treatment No associated syndromes, e.g., Cockayne's syndrome or trichothiodystrophy

PATIENT CHARACTERISTICS: Age: 1.66 to 60 Other: Good general health and mental capacity No illegal drug use No pregnant or nursing women Negative pregnancy test required of fertile women Effective contraception required of fertile women

PRIOR CONCURRENT THERAPY: See Disease Characteristics