# Acne Inversa vs. Pilonidal Sinus: What Should You Distinguish?

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Language: en
Category: Diagnosis
Published: 2026-05-21
Last updated: 2026-05-21
Author: Dr. rer. nat. Dennis Alexander Kwiatkowski (Biochemist, Scientific Writer and Pharma Expert)
Tags: Acne Inversa, Hidradenitis Suppurativa, HS, Diagnosis, acne inversa, pilonidal sinus, tailbone, differential diagnosis

> Symptoms on the buttocks can have different causes. This comparison classifies acne inversa and pilonidal sinus by location, course, and accompanying patterns.

Medical disclaimer: This website is for general educational information only and does not replace medical advice, diagnosis, or treatment. Please speak with qualified medical professionals about symptoms or treatment decisions.

## Article

## When Symptoms "on the Backside" Are Not Clear-Cut

Pain, discharge, or an abscess on the buttocks is often quickly filed away under
a single umbrella term in everyday life. For a medical classification, however,
it makes a difference whether mainly the tailbone and gluteal cleft region is
affected or whether a broader recurring HS pattern is present.

## What Is More Consistent with a Pilonidal Sinus

A pilonidal sinus, often also referred to as a tailbone fistula, typically
affects the region of the gluteal cleft near the tailbone. It can remain
symptom-free, develop an acute abscess, or chronically discharge secretion.

If symptoms repeatedly occur in exactly this region, a pilonidal sinus
definitely belongs in a medical evaluation.

## What Is More Suggestive of Acne Inversa

HS can occur on the buttocks, perianally, or perineally. The suspicion grows
stronger when other typical HS features are also present:

- recurring deep nodules or abscesses,
- additional affected regions such as the armpits, groin, or skin folds under
  the breasts,
- scars, indurations, or tunnels (sinus tracts) following repeated
  inflammation,
- a course that is not limited to a single spot in the gluteal cleft.

Overlaps are also possible. For this reason, "either/or" is not always the best
initial assumption.

## Why the Exact Location Helps

For the consultation, "on the backside" is often too imprecise. It is more
helpful to consider:

1. Is the spot in the central gluteal cleft near the tailbone?
2. Is it more toward the side of the buttocks, perianal, perineal, or in
   several regions?
3. Are there similar lesions in the armpits, groin, or under the breasts?
4. Do openings, scars, or recurring weeping areas remain?

These questions do not replace an examination. They make the findings more
precise for the examination.

## Who Should Classify This?

Recurring symptoms in the tailbone region may require surgical or
coloproctological evaluation. If an HS pattern is also possible at the same
time, dermatological classification is important. In the case of severe pain,
fever, or rapidly increasing inflammation, the area should be medically assessed
promptly.

## References

1. S2k-Leitlinie zur Therapie der Hidradenitis suppurativa / Acne inversa - AWMF, 2024 - https://register.awmf.org/assets/guidelines/013-012l_S2k_Therapie-Hidradenitis-suppurativa-Acne-inversa_2024-08.pdf
2. S3-Leitlinie Sinus pilonidalis, Version 3.0 - AWMF, 2026 - https://register.awmf.org/assets/guidelines/081-009l_S3_Sinus_pilonidalis_2026-04.pdf
3. North American clinical management guidelines for hidradenitis suppurativa, Part I - Journal of the American Academy of Dermatology, 2019 - https://pubmed.ncbi.nlm.nih.gov/30872156/