We present a case of cutaneous lymphoma with photosensitivity. We cons
ider ''cutaneous lymphoma'' as a primary malignant lymphoma of the ski
n, and not as mycosis fungoides. We made an initial diagnosis of actin
ic reticuloid. However, there were some clinical aspects and laborator
y findings which were not compatible with the criteria for actinic ret
iculoid in our case: the age of the patient at onset of the skin erupt
ion was too young, and no severe photosensitivity was found within a w
ide range of ultraviolet radiation. In addition, immunohistochemical e
xamination indicated marked proliferation of CD4(+) T cells in the ski
n. Monoclonal rearrangement of the T cell receptor gene around the inf
iltrating cell was recognized with Southern blotting technique. From t
hese findings, we selected ''cutaneous lymphoma with photosensitivity'
' as the most suitable diagnosis.