**6. Differential diagnoses**

The diagnosis of HS is delayed in most cases due to the numerous possible differential diagnoses, which generates a negative impact on the course of the disease. The differential diagnosis includes a range of possibilities such as anthrax, dermoid cyst, furunculosis, fistulas, abscesses, pilonidal cyst, cutaneous tuberculosis, and inflammatory bowel disease, among others shown in **Table 1** [20, 21].

The most important differential diagnosis of perianal and genital disease is subcutaneous tunneling diseases (e.g., pilonidal disease, Crohn' disease (CD), benign anal fistula, and granuloma inguinale). A biopsy may be performed to elucidate the case. What differentiates pilonidal disease from HS is the absence of midline pits over the


#### **Table 1.**

*Differential diagnosis of hidradenitis suppurativa.*

sacrum. The absence of involvement of the anal canal distinguishes HS from CD and benign anal fistula. About 50% of CD patients develop perianal lesions very similar to HS [20–22].
