I. Introduction

This chapter discusses the clinical features of HS and how to distinguish HS from other conditions that may look like it.

II. Clinical Presentation

HS can be diagnosed based on your physical exam (Table 2.1) and your symptoms. No skin biopsy or lab test is needed for diagnosis.

Three hallmark features of HS include typical lesions, typical distribution of lesions, and chronicity/recurrence (Table 2.2).

HS usually presents after puberty; however, children can also have HS (see Chapter 9 for more information on pediatric HS). The disease can start with occasional painful skin bumps and later involve abscesses, tunnels under the skin, and scars. The classic areas where HS lesions most commonly appear are in skin folds, such as the armpits and groin. Compared to women, men are more likely to also be affected by HS around the anus and buttock areas, as well as in non-classic areas such as the ears and legs. Women tend to be most affected on the frontal areas of the body, such as the breasts and groin.

III. Subtypes of HS

Different clinical subtypes of HS have been proposed. The characteristics of the “classic” HS subtype are: affected armpits and groin, female, and high BMI. Having “non-classic” disease or severe acne are features associated with severe HS.

The “follicular subtype” of HS is characterized by skin lesions such as the pilonidal sinus (a small tunnel at the top of the buttocks), comedones (blackheads), and severe acne. This subtype is more common in males, smokers, and those with a positive family history of HS. Other common characteristics of the “follicular subtype” of HS are increased disease severity and earlier disease onset.

Another subtype of HS, the “gluteal subtype,” is characterized by involvement of the buttocks and is commonly associated with less severe disease and lower BMIs. More research is being done to more accurately describe different subtypes of HS because this information may be helpful in guiding treatment decisions.

IV. Physical Findings and Investigations

HS is a systemic disease associated with several comorbidities like metabolic syndrome and depression, so screening should be done based on HS screening guidelines and clinical clues.

Typical screening may involve blood pressure assessment, hemoglobin A1C (which measures average blood sugar level over the past three months), and cholesterol level measurements. In certain cases, a referral to a gastroenterologist may be needed to evaluate for inflammatory bowel disease. A referral to a psychiatrist or psychologist to address depression, anxiety, or other mental health conditions may be needed.

Hormonal assessments may also be performed if there is evidence of a hormone imbalance. For example, if a female patient has irregular periods. Patients with HS may suffer from arthritis and back pain; therefore, a referral to rheumatology may be required. Referrals for smoking cessation, nutrition counseling, and sexual health counseling may be needed in individualized cases. More information on HS associated conditions and screening may be found in Chapter 6.

Importantly, skin biopsy, lab tests, and bacterial cultures are not needed to make the diagnosis of HS. If labs are checked, you may be found to have a low red blood cell count or high levels of inflammatory markers. You should discuss any lab abnormalities with your healthcare provider.

V. Physical and Emotional Symptoms

You may experience many different symptoms with your HS. Physical symptoms may include pain, itch, odor, drainage, and swelling. Emotional symptoms may include anxiety, sadness, and anger. These symptoms can have a significant impact on your quality of life (for more information, please see Chapter 5).

VI. Conditions that Resemble HS

Early HS lesions can mimic other disorders (Table 2.3). However, the chronicity and progression of HS, as well as the typical involvement of skin fold areas, can help distinguish HS from other conditions. If your healthcare provider is worried that your lesion is a furuncle (a skin infection), a bacterial culture can be performed to help with diagnosis, in addition to clinical information.

Another condition that can look like HS are the skin findings that can be seen in Crohn’s disease (CD). If you have perianal tunnels and are also experiencing gastrointestinal symptoms such as abdominal pain or diarrhea, you should talk to your healthcare provider to make sure you do not have CD. In addition, if you have ulcerative lesions and an anal fistula (an abnormal connection from the skin to the anus) that involves the anal sphincter, these are findings that tend to be suggestive of CD.