Acrodermatitis continua of Hallopeau (ACH) is a rare and severe inflammatory condition that usually affects the hands and feet. It typically begins in the tips of the fingers and toes, with nail involvement, but may spread.

Some doctors consider the condition to be a type of pustular psoriasis. However, others classify ACH as its own inflammatory condition.

Other names for ACH include:

  • acrodermatitis continua suppurativa
  • acrodermatitis perstans
  • dermatitis perstans
  • acropustulosis
  • dermatitis repens

This article explains how to recognize ACH, why it develops, and how to treat it.

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Many doctors classify ACH as a type of pustular psoriasis restricted to one body part. Pustular psoriasis causes symptoms such as pus-filled bumps.

According to the Primary Care Dermatology Society, around 80% of ACH cases begin in one digit. It most commonly affects the thumb first.

The symptoms generally progress in several stages during flares:

  1. The skin under the nail will become red or appear darker.
  2. Painful pus-filled blisters will start to form.
  3. These blisters commonly join together, forming larger lakes of pus. This inflammation can cause the nail to fall.
  4. The finger or toe without a nail remains smooth, but redness, skin scales, and more blisters may form, repeating the process.
  5. Over time, the skin may become thicker.

ACH can lead to blistering on other digits. Alternatively, the blistering may move further up the hand or foot.

Ongoing ACH can lead to a type of bone breakdown that doctors call osteolysis. Many people with ACH will permanently lose some or all of the affected nails.

The exact cause of ACH is not always clear.

ACH often occurs due to a traumatic injury or infection. Reports have also mentioned inflammatory and nerve-related causes of the condition.

Learn about finger infections.

There’s no specific test for ACH. A doctor will typically base an ACH diagnosis on presenting symptoms and a skin biopsy.

The skin biopsy would show certain immune cells but no sign of an infection, as ACH commonly causes sterile blisters.

Tests can also help rule out bacterial and fungal infections.

As ACH is a rare condition, there have been few studies into the effects of different treatments. However, some studies found that two types of treatments might help reduce some symptoms of the condition. These include topical treatments and systemic medications, the latter of which work throughout the whole body.

Topical treatments involve applying them directly to the skin to reduce pain and inflammation. These can include:

Systemic medications may help control the immune system’s response to skin cells. Examples include:

  • acitretin, a retinoid medication
  • cyclosporin, a calcineurin inhibitor
  • infliximab, adalimumab, and etanercept, which are anti-tumor necrosis factor agents
  • methotrexate, an antirheumatic drug
  • photochemotherapy, a type of radiation treatment using UV light
  • secukinumab, an anti-IL-17 monoclonal antibody
  • ustekinumab, a biologic medication
  • secukinumab, an interleukin-17 inhibitor

More research into the efficacy of various treatments for ACH is necessary. A person’s doctor will be able to advise on what treatments they recommend according to the individual’s circumstances.

As ACH is a rare condition, experts do not know exactly how many people develop it.

It is possible that the condition is a type of localized pustular psoriasis. Around 3% of those with psoriasis develop pustular psoriasis, while more than 8 million people in the United States have psoriasis.

Around 46.2% of individuals with ACH also have plaque psoriasis.

Acrodermatitis continua of Hallopeau (ACH) is a rare inflammatory skin condition with possible links to pustular psoriasis. It causes painful blisters on the digits and around the nails, which can lead to nail loss and eventual bone damage. The condition typically begins in the tip of the finger or toe, but it can spread.

Some systemic and topical medications have relieved symptoms. A person’s doctor can help them to create a suitable treatment plan.

It is best to contact a doctor as soon as there are concerns about ACH. The doctor can perform an examination and order a skin biopsy to confirm the diagnosis and rule out other possible causes.