Author: Ken Hiu-Kan Ip, Medical Student, University of Auckland, New Zealand, 2013.
Acrodermatitis continua of Hallopeau (ACH) is a rare inflammatory disease characterised by pustular eruptions beginning in the tips of fingers and toes (digits). The pustules may vary in extent over a chronic, recurrent course.
The disease is named after the French dermatologist François Henri Hallopeau, who described the syndrome in 1880. It is also known as dermatitis repens, acrodermatitis perstans and acropustulosis.
Acrodermatitis continua of Hallopeau is most common in adult females. However, it can also present in males, children and elderly.
Acrodermatitis continua of Hallopeau is often triggered by localised trauma or infection at the distal phalanx (the tip of the digit). 80% begin in only one digit, most commonly the thumb.
During acute flare-ups, the skin of the distal phalanx becomes red and scaly and develops small pustules. The pustules often join together and on bursting, reveal a painful, red and glazed area where new pustules then develop.
Pustulation of the nail bed and its growth site (matrix) can result in onychodystrophy (malformation) and anonychia (loss of nail).
Slowly, the disease can rarely spread proximally to affect the hand, forearm and/or foot. There may be osteolysis (destruction of bone) resulting in a wasted and tapered tip of finger or toe.
In adults, acrodermatitis continua of Hallopeau may evolve into generalised pustular psoriasis. The disease may also affect mucosal surfaces such as the conjunctiva, tongue and urethra.
The cause of acrodermatitis continua of Hallopeau is not completely understood. It is considered a variant of palmoplantar pustulosis and related to psoriasis. It is classified as an autoimmune disorder in which there is localised immune dysregulation in the skin.
Acrodermatitis continua of Hallopeau is diagnosed based on clinical presentation and histological appearance of a skin biopsy examined under the microscope.
The characteristic histopathological feature is intra-epidermal spongiform pustules filled with neutrophils.
There are no specific tests to confirm the diagnosis. Other investigations to consider include Gram stain smear to exclude bacterial infection, and potassium hydroxide (KOH) preparation of the pustules to exclude fungal infection. A culture of pustular fluid is usually sterile, but secondary infection may also occur.
Because acrodermatitis continua of Hallopeau is so rare, there is little evidence on which to base treatment decisions.
Some treatment options reported in the medical literature to be effective include:
Acrodermatitis continua of Hallopeau is a chronic disease that may eventually destroy the nail and underlying bone as described above. Though there are case reports of success with experimental agents such as infliximab, it is often refractory to treatment.
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