Erythema ab igne mimicking livedo racemosa

Overview

The large brown irregularly reticular patch mimicking livedo racemosa developed on the lateral side of the right leg in 66-year-old male. The biopsy showed hyperkeratosis, increased amount of melanin in keratinocytes, mild pleomorphism of keratinocyte nuclei, discrete hydropic degeneration of the basal epidermal layer and a few dyskeratotic keratinocytes in the spinous layer. In the papillary dermis there were scant lymphocytic infiltrates with some erythrocytes, rare siderophages and melanophages perivascularly. This finding is suggestive for erythema ab igne, which was supported by the patient’s history. In winter the patient had been sitting with his right leg 10 cm close to the stove, always only on the same side. The direct immunofluorescence showed faint granular positivity of C3 fraction and fibrinogen in the vessel walls of the superficial dermal vascular plexus. IgA, M and IgG fractions were negative. The finding shows features of vasculitis of the superficial plexus which was, primarily, induced by the physical thermal stimulus, as well as the hydropic degeneration of the basal layer of epidermis and other epidermal changes.

Key words:
erythema ab igne – livedo reticularis – clinical resemblance – histopathology – direct immunofluorescence