How Is Hidradenitis Suppurativa Diagnosed?

Hidradenitis suppurativa (HS)—sometimes also called acne inverse—is a chronic skin condition that causes lesions on your skin that may look like painful bumps or pus-filled abscesses.

Because symptoms of many skin conditions can look similar, getting a proper diagnosis can help you start the treatment you need. Early diagnosis and treatment are essential, as they can help prevent your condition from worsening and lower the risk of complications.

However, an HS diagnosis can be challenging because no specific test definitively diagnoses the condition. In most cases, your healthcare team (which may include your primary care provider and dermatologist) will use several exams—including a physical exam, blood tests, and imaging scans—to determine whether you have HS and understand the severity of your condition.

Diagnostic Criteria

Hidradenitis suppurativa (HS) can be difficult to diagnose because its symptoms often resemble symptoms of other conditions, such as acne, infections, or insect bites. Currently, no specific diagnostic test can definitively determine if you have HS. Because of this, many people with HS don't receive a diagnosis in the early stages of the condition.

As research on HS has improved, researchers have developed diagnostic criteria to make diagnosing HS more accurate and timely. There are three main criteria you have to meet to receive an HS diagnosis:

• Lesions: The presence of deep-rooted lumps or nodules, pockets of pus (abscesses), blackhead-like bumps, sinus tracts (narrow channels that connect multiple lumps), and scars that develop after a bump heals
• Location: Bumps that have developed in areas where the skin touches itself, such as the armpits, inner thighs, genitals, and under the breasts
• Chronicity: Lesions return and often develop on the same area, with a minimum of two lesions developing at the same site within six months

Medical History

If you've decided to go see a dermatologist (a doctor who specializes in skin conditions) about your symptoms, it can help to know what the diagnostic process looks like. During your appointment, you can expect your provider to ask about your medical history. They may ask questions such as:

• What symptoms are you experiencing?
• When did the bumps first appear?
• Are you experiencing pain?
• Do you have additional symptoms that occur alongside the bumps?
  
• Does anyone in your family have HS or another skin condition?

These questions can help them narrow down what condition may be causing your symptoms.

Physical Exam

Your dermatologist will also perform a physical examination to check for signs of HS. They may:

• Take a look at your bumps to check for inflammation, infection, or pus
• Assess whether you're feeling pain
• Check for fluid leakage at the site of your lesions

It's worth noting that dermatologists often collect the fluid from the site of a lesion and send it to the lab to test for a bacterial infection and rule out other causes of your skin symptoms.

Blood Tests

Blood tests are not usually helpful in the diagnosis of hidradenitis suppurativa. However, dermatologists may recommend blood tests to rule out other conditions. You may undergo one or more of the following:

• Complete blood count (CBC): Measures the number of red blood cells, white blood cells, and platelets in the blood
• C-reactive protein (CRP): Determines the presence of inflammation in your body
• Erythrocyte sedimentation rate (ESR): Detects certain proteins in the blood that could be causing inflammation
• Leukocyte count: Checks for a high white blood cell count, which could indicate infections or underlying health conditions

Imaging Scans

In some cases, dermatologists may recommend imaging tests if they suspect HS. These tests can provide a closer look at your lesions and check for damage inside the body. Common imaging tests for HS include:

• Clinical photography: Involves using a smartphone to take photographs of the lesions and helps document any skin changes you're experiencing with HS over time
• Ultrasound: Uses high-energy sound waves to create images of internal tissues and organs of the body to detect the severity of HS and the presence of skin tunneling (or wounds under the surface of the skin)

Stages of HS

If you receive a diagnosis for hidradenitis suppurativa, your healthcare team will determine what stage of HS you're experiencing. The Hurley staging system is the most common one that providers use to stage HS. According to this system, the stages of HS are as follows:

• Stage I: Characterized by single nodules (bumps) or abscesses with no permanent lesions
• Stage II: Characterized by recurrent nodules and abscesses that cause scarring
• Stage III: Characterized by multiple deep lesions that cause widespread scaring

Screening for Related Conditions

Hidradenitis suppurativa can mimic symptoms of other skin diseases, so your healthcare team will also screen you for similar conditions, such as:

• Acne: Pimples
• Carbuncles: Boils under the skin
• Folliculitis: Inflammation of the hair follicles
• Actinomycosis: Bacterial infection
• Epidermoid cyst: Small bumps made of keratin
• Crohn's disease: Inflammation of the digestive tract
• Tuberculous abscess: A rare form of tuberculosis
• Granuloma inguinale: Bacterial infection of the genitals

A Quick Review

Hidradenitis suppurativa is a skin condition that causes painful lesions, such as pus-filled abscesses and widespread bumps that scar the skin. Getting a diagnosis for these symptoms is essential to getting the treatment you need.

No single test can diagnose HS, so healthcare providers use a combination of a physical exam, blood tests, and imaging scans to rule out other conditions and make an accurate diagnosis.