Inverse psoriasis is a skin condition that causes red and inflamed lesions in the skin folds of the body. It is also known as intertriginous psoriasis.

The location and appearance of these lesions set inverse psoriasis apart from other types of psoriasis. Inverse psoriasis appears as a red, smooth, and shiny lesions found in skin folds of the body.

The armpits, groin, under the breasts, and other skin folds are particularly at risk from inverse psoriasis. It can also occur in the genital area.

Researchers believe inverse psoriasis affects between 3 and 7 percent of people with psoriasis.

People who are overweight or who have deep skin folds are more likely to develop inverse psoriasis. People with this condition are more likely to also have other types of psoriasis elsewhere on the body.

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Inverse psoriasis can flare up after some kind of injury or trauma.

The cause of inverse psoriasis is similar to the cause of other types of psoriasis. Psoriasis is an autoimmune condition. It happens when the body's immune system reacts in an unusual way. In psoriasis, this results in an overproduction of skin cells.

Moisture and sweating make inverse psoriasis worse. This is why it occurs in skin folds.

Why some people develop psoriasis is not clear. One theory is that some people inherit the genes that cause psoriasis, and when they are exposed to a trigger, the symptoms develop.

The triggers can vary between individuals, but for inverse psoriasis, sweating and having skin folds makes it worse. A person with excess weight may have more skin folds. This makes them more likely to develop symptoms, if they are prone to psoriasis.

What causes a psoriasis flare-up in one person may not affect another.

Common triggers include:

  • severe stress
  • injuries, such as injections, sunburn, or a scratch
  • certain medications, including lithium and antimalarial tablets
  • infections that affect the immune system, especially strep infections or other common respiratory infections

Other possible triggers that research has not yet proven may include allergies, diet, or even the weather.

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Inverse psoriasis occurs in skin folds. Image credit: Dermnetz.

Inverse psoriasis causes lesions of smooth, shiny skin, usually in skin folds.

A person with inverse psoriasis may also have plaque psoriasis. Plaque psoriasis is the most common type of psoriasis. It involves scaly, inflamed, and red patches of skin on the body.

In inverse psoriasis, the patches often appear smooth and shiny. They do not have the scaly texture of plaque psoriasis.

This is because the patches occur in the skin folds.

In the presence of warmth, moisture, and friction, the appearance of the skin and lesions change.

Complications

Inverse psoriasis can lead to an infection.

This is because:

  • the lesions tend to occur in areas of the body where the skin is thin and sensitive
  • the medications that treat inverse psoriasis can make the skin thinner, increasing the risk of infection
  • skin folds tend to be warm, moist areas that are prone to yeast or other bacterial infections

If the skin becomes injured or opened, an infection may develop.

Co-morbidities

A number of other conditions can occur with psoriasis.

These include:

Current guidelines suggest that doctors carry out regular checks for these and other comorbidities if a person has moderate-to-severe psoriasis.

Whenever there is a change in the skin, a physician should evaluate it and treat it appropriately, to reduce the risk of infection or other complications.

The symptoms of psoriasis often resemble those of an infection. They require treatment, especially as lesions put the skin is at a higher risk of developing an infection.

A person who knows that they have psoriasis may not need to visit their doctor each time they have a flare, especially if they already have medication and are familiar with their condition.

However, if there are any signs of an infection, even a person familiar with psoriasis should see a physician.

Diagnosis

A physician will normally diagnose psoriasis after listening to the person's description of the symptoms and carrying out a physical examination and an inspection of the lesions.

If the lesions occur in an area where the skin rubs against itself, the doctor may diagnose inverse psoriasis.

They may take a skin sample for a culture to rule out other conditions with similar symptoms.

Treating inverse psoriasis can be difficult because it occurs in an area where the skin is thin and sensitive.

Topical treatments

The doctor may prescribe the same steroid creams that people apply to the skin to treat psoriasis. These can be effective.

Side effects may occur because the skin in the affected area will be thin. This increases the absorption of the steroids.

There may also be further thinning of the skin and the appearance of stretch marks.

In addition to topical steroids, some physicians will recommend using tacrolimus or pimecrolimus.

People use these medications to treat eczema, but they have also been successful in managing psoriasis in some people.

The National Psoriasis Foundation recommend not covering lesions with plastic dressings after applying a topical treatment.

UV light therapy

In some cases, the doctor may recommend ultraviolet B (UVB) light therapy with topical creams to manage the symptoms.

Infection

If an infection develops, the doctor may add an antifungal or antibiotic cream to the existing treatment.

Biologics and systemic treatment

A systemic medication works throughout the body. These types of drugs are used for those with moderate to severe psoriasis or when topical medication and light therapy is not effective. An example of a systemic medication is methotrexate.

A biologic is different from a systemic treatment in that it targets a specific part of the immune system. A doctor usually gives these drugs by injection or intravenously (IV). If a person has a diagnosis of inverse psoriasis, a doctor may prescribe etanercept (Enbrel) or infliximab (Remicade) as a biologic treatment.

Side effects with biologics may include a greater tendency to develop infections, as the drugs affect the immune system.

Careful hygiene and self-care can help manage the symptoms. This may improve the appearance of psoriatic patches.

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A moisturizing cream can help reduce the discomfort of psoriasis.

Good practice includes:

  • regular bathing with warm water and mild soaps
  • avoiding harsh soaps and hot water
  • adding bath oil, Epsom salts, or colloidal oatmeal to a bath for extra moisture
  • using a moisturizer every day, or several times a day in especially cold and dry weather
  • practicing regular stress management techniques
  • avoiding alcohol, as it may reduce the effectiveness of some treatments
  • getting a few minutes of sunlight each day
  • losing weight if necessary
  • wearing cotton underwear or clothing next to the skin

Itching can be a big problem. Several anti-itch and cooling lotions are available over the counter to relieve these symptoms. Antihistamine drugs can also relieve itching.

Weeping of wounds is another problem. Talcum powder or cornstarch may help, but people should check first if a product is likely to cause irritation.

Keeping a diary can help a person to pinpoint what causes their symptoms and to avoid those triggers where possible.

Inverse psoriasis can be difficult to treat in some cases, but some lifestyle changes and topical medications can help to bring the symptoms under control.

It is important for people with inverse psoriasis to stay in touch with their doctor, especially if they have a flare-up that does not respond to prescribed medications.

It may also be helpful for people to keep a journal of symptoms and what aggravates or relieves them, to help identify triggers.