Dermatomyositis with Eosinophils

Abstract

Dermatomyositis is an idiopathic inflammatory myopathy that often presents with symmetric proximal skeletal muscle weakness and characteristic skin findings. Typical skin biopsy findings include vacuolar changes of the basal layer, increased dermal mucin, and a predominantly lymphocytic infiltrate. We report a case of dermatomyositis presenting as intensely pruritic papules and plaques, with initial histopathology being atypical of dermatomyositis due to the presence of eosinophils. The initial biopsy demonstrated a superficial dermatitis with eosinophils, initially thought to represent a drug eruption. A second biopsy of the same cutaneous manifestation was performed at a later time given high clinical suspicion for dermatomyositis and demonstrated a more classic vacuolar interface dermatitis with increased mucin and an absence of eosinophils. Notably, increased pruritus was specifically associated with the lesion that demonstrated tissue eosinophilia. The case illustrates the importance of considering tissue eosinophilia in the histologic presentation of dermatomyositis.

Keywords: connective tissue disease; dermatomyositis; diagnostic pitfall; eosinophils; pruritus.

Figure 1

Upper back papules and plaques showing superficial perivascular dermatitis and eosinophils. (A) Clinical presentation, back. (B) Hematoxylin and eosin (H&E) stain, 20× magnification. Site: back. There is a superficial perivascular mixed infiltrate with eosinophils (highlighted by arrows) and increased dermal mucin.

Figure 2

Left arm papules and plaques with interface dermatitis, increased mucin, and an absence of eosinophils. (A) Clinical presentation, arm. (B) Hematoxylin and eosin (H&E) stain, 20× magnification. Site: arm. There is a subtle vacuolar interface (circled) with focal pigment dropout, a superficial perivascular lymphohistiocytic infiltrate and increased dermal mucin.