Granular parakeratosis

What is granular parakeratosis?

Granular parakeratosis is an uncommon skin condition that affects body folds, most often the armpits. It has a characteristic appearance under the microscope.

Clinical features

Granular parakeratosis presents as a red or brown patchy scaly rash in the armpits or in other skin folds. It is sometimes itchy. It mostly affects middle-aged women, but has been reported to affect babies, children and men.

How is it diagnosed?

Granular parakeratosis is diagnosed by skin biopsy. There are distinctive features on histopathology (parakeratosis, hypergranulosis (hence its name), acanthosis, papillomatosis and prominent blood vessels).

What is the cause?

Granular parakeratosis is thought to be provoked by friction, occlusion and sweating. This may induce proliferation and abnormal development of the skin cells (keratinocytes). It is possibly aggravated by certain deodorant components.

It does not appear to be due to infection.

There may be a defect in filaggrin production. This protein is normally present in the upper epidermis.

How is it treated?

Granular parakeratosis may resolve by itself. Treatments that have been reported to be useful include:

• Topical steroids
• Antiseptics
• Topical retinoids
• Keratolytic agents such as lactic acid
• Calcipotriol cream
• Cryotherapy
• Oral isotretinoin
• Botulinum toxin