Granular Parakeratosis

Granular parakeratosis; Intertriginous parakeratotic hyperkeratosis; Axillary granular parakeratosis.

Granular parakeratosis is a rare, benign, inflammatory keratinization disorder that primarily affects intertriginous areas. Histologically characterized by retention of keratohyalin granules within parakeratotic stratum corneum cells, it reflects a defect in the normal conversion of profilaggrin to filaggrin.

Rare. Most common in middle-aged women, but also reported in infants (infantile form). Often associated with topical irritants, occlusion, or friction (e.g., deodorants, zinc oxide, moisturizers, barrier creams).

Belongs to the group of acquired disorders of keratinization. Clinically and histopathologically distinct from psoriasis, eczema, and acantholytic dermatoses.

The exact cause remains unclear. Likely due to a defect in stratum corneum maturation, with impaired degradation of profilaggrin to filaggrin and persistence of keratohyalin granules. Contributing factors include:

• Occlusion
• Mechanical irritation
• Topical products (e.g., antiperspirants, corticosteroids)
• Petrolatum-based ointments
• Moisture and maceration (e.g., diaper dermatitis)

• Erythematous to brownish plaques with a fine, scaly surface
• Sometimes shiny or slightly elevated
• Commonly asymptomatic or mildly pruritic
• Occurs in intertriginous areas: axillae, groin, inframammary region, perianal skin
• In children, typically perianal or diaper area involvement
• Rare generalized or disseminated cases

• Clinical: typical morphology and distribution
• Histology (biopsy):
  • Parakeratosis with retained keratohyalin granules in the stratum corneum
  • Hyperkeratosis, acanthosis, and papillomatosis
  • Absence of neutrophilic microabscesses or marked spongiosis
  • Negative PAS stain
• Rule out differential diagnoses (e.g., fungal infection, psoriasis)

Preferentially affects intertriginous regions: axillae, groin, inframammary folds, perianal area. In infants, mostly confined to diaper region.

Gradually evolving plaques in areas of friction or occlusion. Often linked to use of topical products. No systemic symptoms.

• Thickened stratum corneum with both ortho- and parakeratosis
• Retention of basophilic keratohyalin granules in parakeratotic cells
• Acanthosis and papillomatosis
• No epidermal dysplasia or fungal elements

• Cosmetic concern
• Pruritus or irritation
• Rare secondary infection due to scratching

Benign. Often self-limited after removal of the triggering factor. Chronic or recurrent in cases with ongoing exposure to irritants or occlusion.

Avoidance of occlusive, irritant, or fragranced products in intertriginous areas. Use of breathable clothing and barrier-reducing hygiene.

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