What is inverse psoriasis?
Inverse psoriasis is a subtype of psoriasis. Psoriasis is a chronic, autoimmune skin disorder. Inverse psoriasis is a relatively rare form of psoriasis. It affects between 3 to 7% of people with psoriasis. Other names for this condition include flexural psoriasis and intertriginous psoriasis.
Inverse psoriasis causes symptoms that differ from plaque psoriasis—the most common form of the disease. Instead of thick, scaly plaques, inverse psoriasis looks red, smooth and shiny. It affects skin folds and areas where two skin surfaces rub together, including intertriginous areas and flexural areas. Intertriginous areas are where skin touches skin, such as under the breasts or between the buttocks. Flexural areas are where the body can flex and cause skin to touch, such as the armpit, knee or groin.
The exact cause of psoriasis, including inverse psoriasis, remains unclear. Most likely, genes and other immune system factors predispose some people to the disease. However, there are known inverse psoriasis triggers. Mainly, irritation or infection in the area may trigger the autoimmune response. People who are overweight or have deep skin folds are most likely to get inverse psoriasis. In many cases, people with inverse psoriasis also have other types of psoriasis, such as plaque psoriasis.
Several other skin conditions can affect the same areas and look similar. This makes it challenging to diagnose inverse psoriasis. It’s important to see a dermatologist to get a correct diagnosis for rashes of the skin folds.
Doctors treat inverse psoriasis with topical medicines, light therapy, and biologics. If a yeast or fungal infection is also present, topical antimicrobial medicines are also necessary.
What are the symptoms of inverse psoriasis?
The symptoms of inverse psoriasis differ from the more common plaque psoriasis. Plaque psoriasis causes thick, silvery, scaly plaques usually on the scalp, knees or elbows. Inverse psoriasis affects skin folds and areas where skin touches and rubs together. Common areas for inverse psoriasis include the armpits, genitals, groin, behind the knee, under the breasts, and in the buttocks crease.
Inverse psoriasis typically has the following appearance:
Little or no silvery, scaly skin due to the moist environment where skin touches
Red, smooth, shiny, inflamed or raw-looking areas that can be quite large
Sore, painful skin
There are several other skin conditions that share the same location and appearance. This includes bacterial and fungal infections. Making the correct diagnosis can be challenging. A dermatologist’s expertise can help reach a prompt diagnosis of inverse psoriasis.
What causes inverse psoriasis?
There is not a clear understanding of what exactly causes psoriasis, including inverse psoriasis. Doctors know that all forms of psoriatic disease are autoimmune disorders. This means the immune system turns on the body’s own cells by mistake and starts attacking them. In psoriasis, the skin is the target of the faulty attack: faulty immune system activation causes more production of skin cells as well as inflammation and blood vessel growth at the surface. Why this happens isn’t fully understood, but certain things seem to trigger it.
With inverse psoriasis, irritation or infection is the main trigger. In areas where skin rubs together, friction can cause irritation. These areas also tend to be warm and moist, which softens the skin and contributes to the irritation. This environment also promotes overgrowth of yeast, fungi and bacteria, which further stimulates the immune system. Trauma to skin in these areas can also act as a trigger.
What are the risk factors for inverse psoriasis?
Inverse psoriasis is more common in people who are overweight or have deep skin folds. Often, people who develop it already have another form of psoriasis, such as plaque psoriasis. No differences in sex or other risk factors are known.
Other factors that contribute to skin irritation in intertriginous and flexural areas include:
Living in a hot, humid climate
Participating in activities that chafe the skin
Reducing your risk of inverse psoriasis
It is not always possible to prevent inverse psoriasis since the disease is not fully understood. However, there may be steps you can take to protect skin in areas prone to develop inverse psoriasis. This includes:
Keeping skin dry and cool
Losing excess weight
Moisturizing with a lotion suitable for psoriasis
Using mild, fragrance-free soaps and cleansers
Wearing loose-fitting clothes made of absorbent materials. Women should wear properly-fitting, supportive bras.
If you already have psoriasis, talk with your doctor about your risk of inverse psoriasis. Ask about ways to protect your skin.
How is inverse psoriasis treated?
It can be challenging to treat inverse psoriasis. Because the skin in the affected areas tends to be thinner and more delicate, many topical medicines for psoriasis are too harsh. Topical treatment options include:
Calcineurin inhibitors including pimecrolimus cream (Elidel) or tacrolimus ointment (Protopic)
Vitamin D cream (Calcitrene, Dovonex, Sorilux)
Ultraviolet (UV) B light therapy and biologic drugs are sometimes necessary for severe or persistent cases. If a skin infection is present, your doctor will prescribe an appropriate topical antimicrobial medicine.
What are the potential complications of inverse psoriasis?
Any time the skin barrier is compromised, infection is a concern. The skin irritation of inverse psoriasis increases the risk of skin infection, which can spread into deeper layers of the skin and to the bloodstream. The warm, moist areas where inverse psoriasis tends to occur also contribute to the risk of infection. See your doctor if you have a skin fold rash that persists.