What is Parakeratosis Pustulosa?

Parakeratosis pustulosa is a condition characterized by the deformation of the fingernail or toenail, accompanied by surrounding erythema and often scaling of the overlying skin. It predominantly affects the thumb or index fingernail in young children, although it can occasionally involve other digits, including toenails. The condition is approximately three times more prevalent in females.

Initial manifestations typically involve erythema beneath the free margin of the nail, which subsequently extends to the nail fold, resulting in swelling and the loss of the cuticle. As the condition progresses, thickened skin pushes upward, leading to deformities in the nail plate. Parakeratosis pustulosa is generally not pruritic, though it may cause mild pain .

Causes

The exact cause of parakeratosis pustulosa is not fully understood. While it may be associated with various skin conditions, the specific mechanisms remain unclear in many cases.

Clinical features

An affected nail may exhibit a variety of clinical signs, including:

Subungual hyperkeratosis
Onycholysis
Onychomadesis
Pitting
Transverse ridging
Ragged or absent cuticles
Erythema of the periungual skin
Blister formation on the fingertips

These signs can complicate the differentiation from other dermatological conditions, such as psoriasis and atopic dermatitis, leading to frequent misdiagnosis despite their common occurrence

Diagnosis

Parakeratosis pustulosa is primarily a clinical diagnosis, with diagnostic investigations conducted to exclude other potential nail disorders.

Swab cultures may aid in identifying microorganisms associated with paronychia.
Tinea infection can be diagnosed through the detection of fungal hyphae in skin scrapings.
Biopsy can distinguish between atopic dermatitis and psoriasis, it is infrequently required in clinical practice.

Treatment

There is no specific treatment for Parakeratosis pustulosa .However, most cases tend to improve gradually over time. The following treatments have been occasionally found to be beneficial:

Emollients
High-potency topical corticosteroids
Topical retinoids
Calcipotriol

The duration of lesions can vary, ranging from one week to several years, although recurrences are infrequent.

Written by:

Atheer Alhuthaili, Medical Intern

Revised by:

Naif Alshehri, Medical Intern

References:

DermNet

Medscape