Parakeratosis pustulosa; Blistering distal dactylitis; Fingertip pustulation; Hjorth-Sabouraud disease; Hjorth-Sabouraud Erkrnakung;

Psoriasis-like parakeratosis; onycholysis;  

The French dermatologist Louis Jean Brocq is credited with first describing this condition as "parakeratosis psoriasisformis" in 1921. However, the first case was described by Sabouraud in 1931.

The term “parakeratosis pustulosa” was coined in 1967 by Niels Hjorth and Thomsen.

A clinical presentation of uncertain etiology characterized by acral pustular dermatitis with subungual hyperkeratosis, nail dystrophy, and onycholysis.   

Tosti et al. reported on long-term follow-up of 20 pediatric patients with "parakeratosis pustulosa." In eight children, PKP was considered a clinical manifestation of psoriasis. In four patients, parakeratosis pustulosa was considered a symptom of allergic contact dermatitis, while in two patients, atopic dermatitis may have been responsible for PKP. Complete resolution of the condition was observed in 11 patients.

The results of this study suggest that PKP is not a single entity but rather a clinical “nail symptom” that can be caused by various inflammatory conditions, including nail psoriasis, atopic dermatitis, and contact dermatitis.

The etiology of PP remains unclear. A connection with pustular psoriasis (acrodermatitis continua suppurativa type), atopic dermatitis and contact dermatitis is suspected. However, "thumb sucking" may also play an etiologic role.

Exclusively children ≤5 years old; women > men; 

Fingers, most commonly the tips of the thumb and middle finger are affected. Involvement of the toes is rare.

Vesicles and pustules are present in the hyponychium region, along with pink, eczematous, scaly plaques. The lesions may also extend to the nail folds or the dorsal side of the fingers. Distal onycholysis is present. The nail plate itself may exhibit ridging, while other nail changes, such as thickening or pitting, are rare. 

The histologic features of PP are nonspecific and resemble psoriasis or chronic eczema. They include parakeratosis, hyperkeratosis, acanthosis, intraepidermal pustules, papillomatosis, mild exocytosis and dilated blood vessels in the papillary dermis with perivascular lymphohistiocytic and/or polymorphonuclear infiltrate.

The differential diagnosis of PP includes both non-infectious (acrodermatitis continua of Hallopeau, pustular (e.g. nail psoriasis) and infectious (blistering distal dactylitis) dermatoses.

Since this disease term has not appeared in the literature over the past 10 years and the clinical presentation is only vaguely defined, this diagnosis can be omitted. The term “parakeratosis pustulosa” is problematic in and of itself because it combines a histological phenomenon with a clinical finding (pustulosa).     

1. Bellet JS (2021) Pediatric Nail Disorders. Dermatol Clin 39:231-243.
2. Brocq L (1921) In: Doyn G, editor. Precis – Atlas of Dermatology, Paris, p. 909.
3. Cronin E et al. (1986) Parakeratosis pustulosa. Clin Exp Dermatol 11:643–645.
4. Gaurav V et al. (2022) A Case of Pustules on the Fingertip in a Child. Skin Appendage Disord 8: 435–440.
5. Hjorth N et al. (1967) Parakeratosis pustulosa. Br J Dermatol 79:527–532.
6. Knop M et al. (2021) Skin Diseases of the Hands and Feet in Children. Hautarzt 72: 215–224
7. Pandhi D et al. (2003) Parakeratosis pustulosa—a distinct but less familiar disease. Indian J Dermatol Venereol Leprol 69:48–50.
8. Sabouraud R (1931) Microbial parakeratoses of the fingertips. Ann Derm 11:206–210.
9. Tosti A et al. (1998) Clinical features and long-term follow-up of 20 cases of parakeratosis pustulosa. Pediatr Dermatol 15:259–263.