Psoriasis is a type of autoimmune condition that causes dry, inflamed, raised lesions on your skin. Plaque psoriasis is the most common type, accounting for 80% to 90% of all cases of psoriasis.

Plaque psoriasis may be further classified into subtypes, one of which is ostraceous psoriasis (OP).

In this article, we explore the key symptoms of OP, as well as what causes it, what triggers a flare-up, and what your options are for long-term treatment and management.

OP is a rare type of plaque psoriasis. It causes severe oval-shaped or oyster-like skin lesions that are extremely thick and hard.

OP sometimes occurs alongside psoriatic arthritis (PsA), a type of arthritis that’s most often associated with severe forms of psoriasis.

Like other forms of psoriasis, OP is considered a chronic condition that requires lifelong management and proper treatment of flare-ups to help improve symptoms and overall quality of life.

Ostraceous psoriasis vs. rupioid psoriasis

Both ostraceous and rupioid psoriasis are uncommon types of plaque psoriasis that cause raised lesions on your skin. The main difference is the shape of the plaques. OP plaques are usually oval-shaped, while rupioid psoriasis plaques are cone-shaped.

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In general, plaque psoriasis may cause the following symptoms:

  • thick, raised skin lesions (plaques) that may vary in shape and size
  • scaliness over plaques that may look silver or white
  • dryness and itchiness where the plaques form

OP is characterized by extremely thick and numerous plaques that may grow larger. It’s possible to experience OP lesions in multiple areas of your body, such as your:

  • face
  • scalp
  • chest
  • back
  • arms
  • hands

It’s common for people with OP to also have PsA. If you have PsA, you may experience separate symptoms around your joints. Common symptoms of PsA include:

  • swelling and tenderness in your toes, fingers, and other small joints
  • joint stiffness when you wake up in the morning
  • heel pain
  • swelling or pain above your heel (near your Achilles tendon)

OP is characterized by raised, oval-shaped skin lesions that are thick and hard to the touch. They may look white, pink, or yellow. Click through the following images for examples of what OP may look like.

Like other types of psoriasis, OP is the result of your immune system overacting, causing increased skin cell turnover. These excess skin cells build up on the surface of your skin, leading to the plaques and scales and the chronic inflammation this condition is known for.

While the exact cause of OP and other autoimmune conditions is not known, it’s thought that psoriasis may be triggered by a combination of genetic and environmental risk factors. Factors that may trigger psoriasis may include:

OP is typically diagnosed with a physical exam. A doctor will look at your skin lesions and ask you questions about your symptoms, such as how long you’ve had them and whether they have recently gotten worse. They may perform a biopsy, which involves taking a sample of your skin to send to a lab for analysis.

They will also evaluate your medical history and may ask you about any illnesses or stressors you’ve recently experienced. Additionally, your doctor may ask about your family medical history to find out whether psoriasis or other autoimmune conditions run in your family.

The diagnostic process will also involve ruling out other skin conditions. While psoriasis may sometimes be mistaken for other inflammatory skin diseases, such as eczema, the severity of OP typically distinguishes it as a type of plaque psoriasis. The shape of the lesions can give your doctor clues about its subtype.

A doctor may also refer you to a specialist, such as a dermatologist, for further testing and treatment.

Medical treatment is critical to address severe plaques associated with OP while helping to prevent the condition from worsening.

In general, doctors may treat psoriasis with a combination of topical medications, immunosuppressants, and retinoids, depending on type and severity.

One recent case report suggests that emollient creams and high dose corticosteroids, as well as an oral immunosuppressant called cyclosporine, may be effective for treating OP.

Biologics can also be used to treat severe psoriasis when traditional therapies aren’t working.

As for nonprescription treatments, the American Academy of Dermatology Association says that most over-the-counter (OTC) remedies, such as hydrocortisone and coal tar, tend to be helpful only in mild cases of psoriasis.

However, you may benefit from using a moisturizer, even if you have a more severe form of psoriasis such as OP. This can help support dry, itchy skin. For best results, apply a fragrance-free moisturizer to damp skin within 3 minutes of washing your hands or bathing.

Does ostraceous psoriasis have flares?

Yes. OP is a chronic condition that may occasionally flare up. Along with treatment and prevention techniques, it’s important to avoid your psoriasis triggers when possible. Common triggers include stress, infections, skin injuries, and dry weather.

Is ostraceous psoriasis curable?

No. Like other types of psoriasis (as well as PsA), OP is considered a chronic condition that can’t be cured. However, treatment can help you manage the symptoms and prevent future flares.

Can psoriatic arthritis turn into ostraceous psoriasis?

PsA rarely develops before psoriasis does. In fact, most people have psoriasis for several years before developing PsA.

Still, the more severe your psoriasis is, the greater the risk you might develop PsA in the future. This may explain why individuals with OP, a severe type of plaque psoriasis, may be more likely to have PsA as a comorbidity (a co-occurring condition).

Does ostraceous psoriasis get worse the longer you have it?

Without treatment, OP may worsen and possibly progress to PsA. These severe conditions can be debilitating and decrease overall quality of life, so early treatment to prevent progression is critical.

Is ostraceous psoriasis hereditary?

OP specifically — and psoriasis more generally — isn’t directly inherited. However, autoimmune disorders may run in families, though you may not get the same type that one of your relatives has. For example, one family member might develop plaque psoriasis, while another might have rheumatoid arthritis.

OP is a severe type of plaque psoriasis, an autoimmune disease known for causing thick, oval-shaped, scaly skin lesions that may be itchy and painful. OP has more severe symptoms than plaque psoriasis.

Prompt treatment of OP is important for quality of life and can help prevent the condition from progressing into worsening lesions and possibly PsA.

If you’re experiencing symptoms that could be linked to psoriasis, consult a doctor right away. They can help accurately diagnose your condition and recommend treatment.