Background: Pustular eruptions of the extremities of the fingers and toes (acropustulosis) have been grouped under the single term "Hallopeau's acrodermatitis continua", which is a severe disease, with uninterrupted course, and successive eruptions that may become generalized. However, there is a form of acropustulosis with few lesions, evolving with remissions and relapses, with a benign course. It is necessary to separate these two forms of acropustulosis.
Methods: I had the opportunity to observe six patients with a mitigated form of acropustulosis that does not fit into the diagnostic criteria of Hallopeau's acrodermatitis continua, which should be considered an independent clinical entity.
Results: Sometimes, there is only one lesion in each eruption. The pustules are sterile and appear in small crops, located on the hyponychium or on the nail bed. The result is partial onycholysis or nail detachment. After each eruption there is complete recovery. Histopathology shows a nonspongiform pustule filled with neutrophils, with subcorneal localization. Four patients had follow-up for at least 2 years, and one patient presented psoriasis lesions on the scalp after 11 years.
Conclusions: Acropustulosis as I described it can be differentiated from Halopeau's acrodermatitis continua using the following diagnostic criteria: (1) it is a benign condition; (2) the pustules are located on the hyponychium or nail bed; (3) pustules can be single or occur in small groups; (4) they reccur in flares, with restitutio ad integrum during the periods of remission; (5) the pustules are sterile; (6) microscopic study shows a subcorneal pustule (spongiform aspect is rare). A similar condition to that found in my cases was described by Radcliff-Crocker (H. Radcliff-Crocker, Diseases of the Skin, London: H.K. Lewis, 1888), termed "dermatitis repens".