How Is Psoriasis Diagnosed?

Psoriasis is a chronic autoimmune condition that causes symptoms called plaques to develop on the skin. Plaques are patches of raised, reddened skin that are covered in a layer of silvery scales. People with psoriasis have an immune system that is overactive and with chronic levels of inflammation. This inflammation causes the body to produce too many new skin cells, pushing older skin cells to the surface where they build up as plaques.

A person can develop symptoms at any age, although around three-quarters of people with psoriasis are diagnosed before the age of 401. Many people are diagnosed with psoriasis when they tell their primary care provider (or other healthcare provider) about symptoms that they have developed on their skin.

If a person has symptoms that look like they may be caused by psoriasis, the healthcare provider carries out a physical examination of the symptoms on the affected skin, as well as taking the person’s medical history. At this time, there is no specific blood test or other test that can be used to diagnose psoriasis. Usually, physical exam and medical history are enough for the healthcare provider to make the diagnosis2.

What happens during the physical examination?

During the physical examination, healthcare providers look closely at the area(s) of skin that are affected by symptoms. They may lift a small layer of scale from the top of a plaque to see if it leaves a smooth, red surface with tiny spots of blood. This is called the Auspitz sign, which is common in psoriasis plaques1. The healthcare provider also examines your skin, scalp, nails, and the inside linings your eyelids, nose, and mouth.

During the exam, the healthcare provider will also check to see if you have symptoms of other types of health conditions that occur more commonly among people with psoriasis3. These include:

However, some people may need to have a biopsy to find out if the symptoms are being caused by psoriasis or some other condition, such as eczema, that causes similar types of symptoms to develop on the skin2. A biopsy involves taking a very sample of the affected skin so that it can be examined more closely under a microscope. Biopsies are generally quick procedures that that can be performed in a healthcare provider’s office.

Read more information about physical examinations and diagnosing psoriasis.

Read more information about biopsies.

Why does the healthcare provider need to take a medical history?

During the process of diagnosing psoriasis, your healthcare provider will take your medical history. This involves asking you questions about your symptoms as well as questions about your general health, your family’s health history, and your overall lifestyle2. These are important questions because it helps your healthcare provider get a better understanding about things in your life that may be making your symptoms worse or better, as well as risk factors that make you more likely to develop the condition.

Learning about your family’s health history is important because the tendency to develop psoriasis has a genetic link that is passed down through families: around one-third of people with psoriasis have a family member who also has the condition1. For example, if your parent or sibling has psoriasis, then it is more likely that your own symptoms are being caused by psoriasis as well.

What other conditions have symptoms that are similar to psoriasis symptoms?

The process of diagnosing psoriasis involves ruling out other conditions that often have similar symptoms. Your healthcare provider may call this process a differential diagnosis. Visiting a dermatologist may help confirm a diagnosis of psoriasis. Conditions that may present with similar symptoms of the skin include:2,4

  • eczema (atopic dermatitis)
  • seborrheic dermatitis
  • ringworm (tinea corporis)
  • Pityriasis rubra pilaris
  • Pityriasis rosea
Written by: Anna Nicholson | Last reviewed: July 2016.
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