Which histologic findings are characteristic of erythema dyschromicum perstans (EDP)?

Updated: Apr 19, 2019
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Dirk M Elston, MD  more...
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Answer

The biopsy specimen is obtained as much to rule out other diagnoses as to confirm that of erythema dyschromicum perstans because the erythema dyschromicum perstans histologic pattern is relatively nonspecific. One should attempt to obtain a biopsy sample of the border of an active macule, which usually demonstrates mild basal cell layer vacuolar degeneration overlying an upper dermis with a mild perivascular mononuclear cell infiltrate and increased melanophages.

Distinguishing ashy dermatosis from lichen planus pigmentosus (LPP) is not always easy. A Mexican study of 20 patients with erythema dyschromicum perstans and 11 with LPP provided clear clinical delineation between the 2 often histologically indistinguishable disorders. [31] LPP has pruritic brownish black macules or patches, with no active border, on the face and the flexor folds. Erythema dyschromicum perstans does not involve mucosal surfaces, where LPP does. In favor of erythema dyschromicum perstans being either a subset of idiopathic lichen planus or a lichenoid drug eruption are reports of lichen planus and erythema dyschromicum perstans occurring in the same patient, the clinical resemblance of erythema dyschromicum perstans to atrophic lichen planus, and similar histologic patterns with immunofluorescence in both erythema dyschromicum perstans and LPP.

The border of an active erythema dyschromicum perstans lesion and the border of an LPP lesion often both show hyperkeratosis, a thinned epidermis, hydropic degeneration of the basal layer, pigment incontinence, and a perivascular lymphohistiocytic infiltrate (see the images below). Colloid bodies are occasionally seen in both.

Photomicrograph of a lesion on the patient's back Photomicrograph of a lesion on the patient's back shows slight basilar vacuolar change, extensive pigment incontinence, dilatation of dermal lymphatics, and lack of inflammation (hematoxylin & eosin, original magnification X24.8). Reprint with permission from Cutis 1986; 37: 42-44.
Higher-power photograph shows slight vacuolar basi Higher-power photograph shows slight vacuolar basilar change, marked dilatation of intradermal lymphatics, incontinence of melanin pigment, and lack of inflammation (hematoxylin & eosin, original magnification X238). Reprint with permission from Cutis 1986; 37: 42-44.

Immunopathologic study of erythema dyschromicum perstans shows immune-associated (Ia) antigen expression in keratinocytes and strong OKT 4 and OKT 6 staining of Langerhans cells. It also shows dermal infiltration by T lymphocytes of both helper-inducer and suppressor-cytotoxic phenotypes, a pattern commonly seen with lichen planus. CD36 expression is evident in the viable upper epidermis on lesional keratinocytes, which may imply a delayed hypersensitivity reaction. Beneath, in the dermis, the cellular infiltrate has been found to express CD69 and the cytotoxic cell marker CD94. In addition, as with lichen planus, the colloid bodies stained immunoglobulin G positive.

Ultrastructural findings demonstrate immature, small, irregular-shaped melanosomes in melanocytes and peripheral localization of melanosomes in keratinocytes. [32]


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