Chronic actinic dermatitis: an immunohistologic and photobiologic study.

Photobiologic, histologic, and immunohistochemical findings in 14 patients with chronic actinic dermatitis were compared. Grading of routine histologic features of involved skin demonstrated a spectrum of abnormalities ranging from changes resembling chronic dermatitis to those of cutaneous T cell lymphoma. Immunohistochemical staining showed dermal infiltrates to consist predominantly of T lymphocytes, with a significant trend toward lower CD4+/CD8+ ratios in cases with more florid histologic findings. Circulating CD4+/CD8+ cell ratios were normal in five patients and reduced in one patient. Photosensitivity extending to wavelengths longer than 340 nm was detected in eight patients, but the spectrum of photobiologic abnormality did not appear to correlate with either grading of histologic severity or variation in T cell subsets in lesional skin.