Granular Parakeratosis: A Comprehensive Review and a Critical Reappraisal

Abstract

Granular parakeratosis (GP) is a rare, idiopathic, and benign skin condition that presents classically as erythematous to brown hyperkeratotic papules that can coalesce into plaques. Axillary GP was initially observed by Northcutt and colleagues and has since been described in various other areas of the body including other intertriginous and non-intertriginous sites. The term "granular parakeratosis" is now used to describe not only the skin condition, but also a distinctive histological reactive pattern on biopsy specimens that are either regarded as the disease itself, or merely as an incidental finding. Upon review of the current findings, opinions, and associations of this entity, we propose the reappraisal of GP as a reactive pattern, rather than a distinct entity.

Granular parakeratosis induced by benzalkonium chloride exposure from laundry rinse aids

“…Granular parakeratosis classically presents as an annular eruption of erythematous to brown hyperkeratotic papules, coalescing to plaques . It primarily affects intertriginous zones such as the groin and axilla, but can also occur in other areas.…”

“…It primarily affects intertriginous zones such as the groin and axilla, but can also occur in other areas. Historically, granular parakeratosis was thought to be due to exposure to personal hygiene products such as deodorants and antiperspirants, and to products containing zinc oxide . Recent reviews have speculated that granular parakeratosis may be more of a reactive pattern than a distinct disease entity .…”

“…Historically, granular parakeratosis was thought to be due to exposure to personal hygiene products such as deodorants and antiperspirants, and to products containing zinc oxide . Recent reviews have speculated that granular parakeratosis may be more of a reactive pattern than a distinct disease entity . Granular parakeratosis involves the alteration of keratinocyte maturation from the stratum granulosum to the stratum corneum and consequently retention hyperkeratosis .…”

“…Recent reviews have speculated that granular parakeratosis may be more of a reactive pattern than a distinct disease entity . Granular parakeratosis involves the alteration of keratinocyte maturation from the stratum granulosum to the stratum corneum and consequently retention hyperkeratosis . This is thought to be caused by a defect in the processing of profilaggrin to filaggrin, resulting in retention of keratohyaline granules, elevation of stratum corneum pH and consequently increased adhesion and defective barrier function …”

Focal Acral Hyperkeratosis with Intracorneal Retention of Keratohyalin Granules

“…This case is depicted due to the conspicuous retention of keratohyalin granules in the affected stratum corneum, akin to that described in cases of granular parakeratosis (GP), but without the presence of intracorneal nuclei (parakeratosis) or axillary /intertriginous lesions, characteristic of GP. [7] To our knowledge retention of keratohyalin granules had never been describe-ed in FAH and could merely represent a reaction pattern to external irritation (shaving) as suggested by others for GP. [8] Alternatively, retention of keratohyalin granules could relate to a primary defect of cornification in patients with FAH and if reproducible could potentially serve as a histopathological discriminator from AKE.…”