A study of persons developing skin lesions following sun exposure is conducted. The lesions are not found on skin protected from ultraviolet light. Biopsies of involved skin show immunoglobulin G deposition along the dermal-epidermal junction, along with vacuolization of the basal layer and a perivascular lymphocytic infiltrate. No other organ involvement is present. Which of the following diseases do these patients most likely have?

The more benign discoid lupus involves just skin, unlike systemic lupus erythematosus, but is still a form of type III hypersensitivity with antigen-antibody complex deposition along the basement membrane of the epidermis. The other listed options are not associated with sun exposure. Bullous pemphigoid lesions occur at the dermal-epidermal junction from antibody deposition targeting type XVII collagen as a component of hemidesmosomes. Dermatitis herpetiformis associated with celiac disease has IgA antibodies deposited at tips of dermal papillae. Dysplastic nevi develop in relation to mutations in genes encoding for growth control proteins. A toxic epidermal necrolysis is a severe form of erythema multiforme mediated by cytotoxic CD8+ cells targeting epidermal basal cells. Early lesions of discoid lupus erythematosus appear as well-demarcated scaly purple macules or papules and later expand into discoid plaques. Microscopically there is basal vacuolar degeneration, areas of epidermal atrophy, acanthosis, keratotic follicular plugging, basement membrane thickening, and superficial and deep perivascular lymphocytic infiltrate.