BACKGROUND: Granular parakeratosis is suspected to result from an error in epidermal differentiation, leading to variably pruritic, hyperpigmented-to-erythematous patches and plaques. Characteristic histopathologic features include a thickened stratum corneum, compact parakeratosis with retention of keratohyalin granules, vascular proliferation, and ectasia. The pathogenesis of this entity is uncertain. METHODS: We present a case of axillary granular parakeratosis and review the literature. RESULTS: The lesion showed a thickened stratum corneum with compact parakeratosis, slight epidermal hyperplasia, and a sparse perivascular lymphohistiocytic infiltrate. Keratohyalin granules were diffusely present within the parakeratotic stratum corneum, and the retained granular layer showed focal vacuolization. CONCLUSIONS: Granular parakeratosis is a rare form of parakeratosis most often seen in the axilla, although other intertriginous areas may be affected. Unique histopathologic findings allow for a specific diagnosis to be made. Although an irritant contact reaction appears causative, mechanical irritation may also play a role in inducing these skin changes.
BACKGROUND:Granular parakeratosis is suspected to result from an error in epidermal differentiation, leading to variably pruritic, hyperpigmented-to-erythematous patches and plaques. Characteristic histopathologic features include a thickened stratum corneum, compact parakeratosis with retention of keratohyalin granules, vascular proliferation, and ectasia. The pathogenesis of this entity is uncertain. METHODS: We present a case of axillary granular parakeratosis and review the literature. RESULTS: The lesion showed a thickened stratum corneum with compact parakeratosis, slight epidermal hyperplasia, and a sparse perivascular lymphohistiocytic infiltrate. Keratohyalin granules were diffusely present within the parakeratotic stratum corneum, and the retained granular layer showed focal vacuolization. CONCLUSIONS:Granular parakeratosis is a rare form of parakeratosis most often seen in the axilla, although other intertriginous areas may be affected. Unique histopathologic findings allow for a specific diagnosis to be made. Although an irritant contact reaction appears causative, mechanical irritation may also play a role in inducing these skin changes.