How to Diagnose Psoriasis

Psoriasis is an autoimmune disease because the immune system attacks skin cells as if they were harmful. This results in thick, red, scaly patches of skin that can be seen during a physical exam and is usually enough to diagnose psoriasis.

When the diagnosis is uncertain, providers may also perform a skin biopsy to collect a tissue sample that can be examined under a microscope.

This article covers everything your doctor will look for during the exam and what they may ask about your medical history. You’ll also learn how a biopsy is done and what else you might have if you don’t end up being diagnosed with psoriasis.

physical examination

There are a number of health conditions that can cause itchy, scaly skin and rashes. In most cases, a healthcare practitioner—especially a dermatologist who specializes in skin diseases—can tell whether your symptoms are due to psoriasis or something else based on vision alone.

For a closer look, they may look at your skin through a dermoscopy. This simple handheld tool has a light and a magnifying glass. It allows your doctor to “magnify” your skin.

medical history review

They will also take some time to ask you some questions.

There are several types of psoriasis. Some symptoms may affect your skin, so your doctor may ask if there are other problems that are bothering you as well. Some of these issues include:

  • Blepharitis (inflammation of the eyelids)
  • uveitis (inflammation of the middle tissue layer of the eye)
  • Joint pain (as seen in psoriatic arthritis)

It is also expected that you will be asked about your medical history. You’ll be asked if you’ve noticed any symptom patterns, in addition to other conditions you’re experiencing.

When preparing for your visit, it can be helpful to write down when you had flares, how long they lasted, what symptoms you had, and if anything seemed to make them better or worse. Also be aware of any treatments or illnesses that occur during the flare.

Additionally, they may ask if you have any other risk factors for psoriasis, such as:

  • Family history of psoriasis or other skin conditions
  • recent streptococcal infection
  • Recent vaccines
  • a disease that weakens the immune system, such as HIV
  • other autoimmune diseases, such as celiac disease, Crohn’s disease, or thyroid disease


The diagnosis of psoriasis begins with a physical examination. Your doctor will examine your skin and check you for other symptoms, such as joint pain and eye inflammation. They will also ask you if there are any other factors that may put you at risk for psoriasis.

Labs and Testing

A rash can develop for many different reasons. So if your rash doesn’t look like a typical psoriatic rash, your dermatologist may perform a skin biopsy.

In particular, they may obtain tissue samples through a needle biopsy.

This procedure is done in the doctor’s office with a local anesthetic to numb the skin. A tubular device that snaps when pressed (similar to a paper clip hole punch) to remove a small piece of skin.

The tissue sample is stained with a blue dye called hematoxylin-eosin. This helps to see skin cells under a microscope.Psoriasis, the appearance of skin cells Acanthus (dense and compact).

There are no other tests to confirm psoriasis, but your doctor may order some if they think there are other possibilities for your symptoms.

It usually takes about a week to get skin biopsy results. In the meantime, your doctor may treat your pain and discomfort.

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Types of Psoriasis

Part of the diagnosis is determining the type of psoriasis you have. This gives your doctor a baseline from which to monitor your condition for any changes. It can also help if you have a type that needs more specialized treatment.

Everyone has their own unique characteristics that vary from person to person. Also, some types differ in that they tend to affect a certain part of the body.

About 80 to 90 percent of people with psoriasis have plaque psoriasis, which causes red, dry skin covered with silvery-white scales. These skin patches tend to appear on the elbows, knees, scalp and back.

Other possibilities include:

  • Nail psoriasis: This type usually occurs with skin psoriasis, but it can also occur alone. It can cause indentations (dimples) on the nails and changes in nail color. The nail plate can also be lifted from the nail bed and chipped.
  • Guttate psoriasis: The telltale sign of this type is a pale, pink rash shaped like a teardrop. It tends to develop after a bacterial or viral infection, such as strep throat or chickenpox. Most common in children.
  • Pustular psoriasis: This type of skin develops red patches and pus-filled blisters, usually on the soles and/or palms of the feet.a more severe form called Von Zumbusch Psoriasiscan affect the entire body and may require hospitalization.
  • Inverse psoriasis: This type is less common, but more likely to occur in people who are overweight. It causes rashes to form in skin folds, such as the armpits and groin, under the breasts, and between the buttocks. The rash may look moist instead of dry and scaly.
  • Scalp psoriasis: This causes patches of thickened skin to appear on the scalp. The plaques are often itchy and can lead to hair loss.

There may be more than one type of psoriasis. For example, you may have plaque psoriasis for several years before the second type of psoriasis develops. Or, your plaque psoriasis may later turn into another, possibly more severe, form of psoriasis.

Causes and Risk Factors of Psoriasis

PASI classification

If your doctor finds out that you have psoriasis, they may use the Psoriasis Area and Severity Index (PASI) to classify the severity of your condition. The index grades your condition based on the severity of your symptoms.

Symptoms in your head, arms, trunk, and legs are assessed visually. No special tools or tests are required.

Each symptom for each body part has a value. These values ​​are then added to obtain the final PASI score. The higher the value, the more severe your condition.

The PASI reference values ​​are as follows:

  • erythema (redness) on a scale of 0 to 4
  • Induration (thickness), on a scale of 0 to 4
  • desquamation (zoom), on a scale of 0 to 4
  • The percentage of skin involved, from 0% to 100%

By establishing a PASI score at diagnosis and repeating PASI every few months, your dermatologist can track your response to treatment.


Your dermatologist may perform a needle biopsy to verify the cause of your skin symptoms. If it’s psoriasis, they may use the Psoriasis Area and Severity Index (PASI) to grade how severe your condition is. PASI may repeat every few months.

Factors Affecting the Prognosis of Psoriasis

Differential diagnosis

Many skin conditions can cause symptoms that look like psoriasis. It’s always possible that you’ve been diagnosed with a different condition at first, such as a drug allergy or fungal infection, only to be diagnosed with psoriasis later.

On the other hand, it’s also possible to suspect psoriasis when it’s actually another condition that’s causing your symptoms.

Some of these are serious, so your doctor may want to do some tests to rule them out before confirming what you have. This process is called differential diagnosis (DDx).

Diseases that can mimic psoriasis include:

  • Atopic dermatitis (eczema), which causes dry and itchy patches on the skin
  • Contact dermatitis, a dry and itchy rash caused by exposure to allergens or irritants
  • Reiter syndrome, a symptom of reactive arthritis, triggered by an infection
  • lupus, an autoimmune disease that affects multiple tissues
  • Lichen simplex chronicusthickening of the skin caused by chronic friction and itching
  • Onychomycosisa nail fungus that causes nails to fall off the nail bed
  • awhich can cause an oval rash on the chest, abdomen, or back
  • Squamous cell skin cancer, which affects the superficial layers of the skin
  • seborrheic dermatitis (dandruff), dry and flaky scalp
  • Tinea corporis (ringworm), a red and itchy circular rash caused by a fungus


Most dermatologists can tell if you have psoriasis by looking at your skin up close. They may take a tissue sample and examine it under a microscope to make sure your rash isn’t caused by something else and to confirm a psoriasis diagnosis.

Many medical conditions can cause skin symptoms that look and feel like psoriasis. Some of these can be serious, which is why it’s important to have your doctor check for any changes in your skin.

VigorTip words

Many things can trigger a psoriasis flare-up, from infections to the weather. Since the condition is chronic, this can be stressful.

Unfortunately, stress is also a common trigger for psoriasis. It’s easy to see how all of this could lead to the next flare.

If stress is making your psoriasis worse, try learning techniques to manage it, such as yoga or meditation. You may also consider seeking help from a licensed therapist.

Frequently Asked Questions

  • Can psoriasis be detected with a blood test?

    No, there is no specific blood test used to diagnose psoriasis. However, blood tests can help rule out other diseases. For this reason, your doctor may order blood tests.

  • How Do Dermatologists Diagnose Psoriasis?

    Psoriasis is diagnosed by a physical examination and sometimes a skin biopsy. A small piece of tissue is removed from the affected area and viewed under a microscope. A biopsy can be done in a doctor’s office.

  • What conditions can be mistaken for psoriasis?

    Several skin conditions may resemble psoriasis. These include eczema, contact dermatitis, lupus, lichen simplex chronicus, onychomycosis, pityriasis rosea, squamous cell skin cancer, dandruff and ringworm.

How to Treat Psoriasis