Hidradenitis Suppurativa (HS)

What Is It?

Why Does It Occur? (The Mechanism)

1. Follicular hyperkeratosis - The hair follicle opening gets plugged with keratin (dead skin cells) and sebum (oil)
2. The blocked follicle ruptures - releasing keratin, bacteria, and hair fragments into the surrounding dermis
3. This triggers a massive inflammatory response - forming painful, tender, red nodules that fill with pus
4. The body tries to wall off the infection, forming sinus tracts (tunnels under the skin)
5. Secondary bacteria (S. aureus, Streptococcus, gram-negatives) worsen the infection
6. As one area heals with scarring, the underlying disease process moves to adjacent follicles - causing the next flare

• Friction from skin folds (worsened by obesity)
• Hormonal factors (androgen excess - why it starts after puberty)
• Smoking (major risk factor)
• Metabolic syndrome / obesity / diabetes
• Genetic mutations in gamma-secretase genes (NCSTN, PSENEN, PSEN1) in severe cases
• Bailey & Love's Surgery notes: "Occlusion of gland ducts leads to bacterial proliferation, gland rupture and spread of infection... with multiple communicating subcutaneous sinus tracts."

Why Does It Keep Coming Back After Surgery?

• Simple incision and drainage (I&D) does NOT cure HS - it only drains the current abscess. The disease process in the surrounding follicles and sinus tracts remains
• The only surgical approach that reduces recurrence is wide radical excision - removing ALL apocrine gland-bearing skin in the affected area, often requiring skin grafting or flap closure
• Even wide excision has post-surgical recurrence rates of 20-40% in some studies, though much lower than I&D
• A 2026 systematic review (PMID: 41229081) confirms outcomes vary significantly by surgical technique, with wide excision offering the best results
• A 2025 study on post-surgical recurrence identified obesity, anatomical location, and inadequate excision margins as key recurrence predictors

Symptoms (Classic HS)

What You Should Do Now

1. See a Dermatologist with HS expertise - not just a general surgeon
2. Ask about biologic therapy - Adalimumab (Humira) is the only FDA-approved biologic for HS. It suppresses the underlying TNF-alpha-driven inflammation and can significantly reduce flare frequency
3. Ask about wide radical excision - if surgery is planned again, ensure it is true wide excision with adequate margins, not just I&D
4. Lifestyle modifications - weight loss (if applicable), smoking cessation, loose-fitting clothing, chlorhexidine washes, avoiding friction
5. Long-term antibiotics - the clindamycin + rifampin combination (300 mg each, twice daily) has good evidence for suppressing HS

Important: HS after 19+ years of active disease carries a small but real risk of squamous cell carcinoma developing in chronic sinus tracts. This is another reason to get proper specialist care.

Revised Differential Diagnosis (Biopsy Negative for HS)

1. Recurrent / Infected Epidermoid Cyst (Most Likely if Male)

• Characteristic: Smooth, firm nodule with a central punctum (small dark dot)
• When infected: becomes painful, red, swollen
• Biopsy of just the pus/fluid would be "negative" for HS
• Cure requires complete excision of the entire cyst capsule - not just drainage

2. Pilonidal Sinus Disease (If in Natal Cleft / Buttock Area)

• Affects young adults, more common in males, hirsute/obese individuals
• Location: classically the natal cleft (between buttocks) - but can extend to nearby areas
• Recurs after I&D if the midline pits and full sinus tracts aren't excised
• Sabiston Surgery: "The cavity should be thoroughly curetted, removing all the embedded hair... hair removal by trimming, shaving, waxing, or laser depilation has been shown to be effective in decreasing recurrence rates."

3. Cutaneous Crohn's Disease / Perianal Fistula (If Near Anal Area)

• Crohn's disease can cause skin manifestations with painful recurring nodules and draining fistulae in the groin/perianal region
• "Knife-cut" deep ulcers are characteristic
• Biopsy would show granulomas (not HS features)
• Would need colonoscopy to rule out

4. Endometriosis of the Groin/Inguinal Area (If Female)

• Cyclical pain (worse with menstruation)
• A swelling that grows and shrinks with the menstrual cycle
• Recurrence after incomplete excision
• Biopsy negative for HS
• Fischer's Surgery: "Extra pelvic endometriosis presents as a painful mass with symptoms that wax and wane with the menstrual cycle... inguinal involvement is likely to be spontaneous."

5. Actinomycosis

What You Should Do

Could you tell me: what is the exact location (groin, armpit, buttock crease) and are you male or female? This will help narrow it down much further.

The Most Likely Diagnosis: Inguinal / Extrapelvic Endometriosis

What Is Inguinal Endometriosis?

• A painful, firm, tender lump in the groin
• Pain and swelling that waxes and wanes with the menstrual cycle - the lesion responds to estrogen just like the uterine lining, swelling and bleeding internally around your period
• Apparent "resolution" between cycles, then return - explaining your 4-5 month pattern
• Each surgery removes the visible mass but if pelvic endometriosis deposits are not also treated (requiring laparoscopy), new lesions regrow from the same hormonal source

Why the Biopsies May Have Been "Negative"

Why Do You Keep Having to Get Surgery?

• Each previous surgery likely drained or removed only the surface lesion in the groin
• The root cause - endometrial deposits in the pelvis (on ovaries, fallopian tubes, uterosacral ligaments, or peritoneum) - was never addressed
• These pelvic deposits continue producing estrogen-driven signals that cause re-implantation and regrowth in the inguinal area
• Without postoperative hormonal therapy, recurrence after surgery alone is 20-40% within 5 years

What You Need to Do - Specific Action Plan

1. See a Gynecologist specializing in Endometriosis - not a general surgeon. This is now a gynecological problem, not a purely surgical skin problem.
2. Request a Pelvic MRI - this can visualize endometriotic deposits in the inguinal canal, round ligament, and pelvis. Look specifically for T2-hypointense fibrotic tissue with hemorrhagic foci (the characteristic MRI appearance of endometriosis).
3. Request a Pelvic Ultrasound - can detect ovarian endometriomas ("chocolate cysts") which often accompany inguinal endometriosis.
4. Track your symptoms vs. menstrual cycle - does the lump get worse, bigger, or more painful in the days before or during your period? If yes, this strongly points to endometriosis.
5. Next surgery (if needed) must be done differently:
   • Complete excision with 1 cm clear margins (not just I&D)
   • Simultaneous diagnostic laparoscopy to find and treat pelvic endometriosis deposits
   • Postoperative hormonal suppression (GnRH agonists like Lupron, progestins, or the combined pill) to prevent regrowth
6. Biopsy re-examination: Ask your doctor to re-examine the previous biopsy specimens specifically for ectopic endometrial glands and stroma if tissue was preserved.

One key question for yourself: Does the lump or pain get noticeably worse around your period (menstruation)? This single symptom - called "catamenial" (cycle-related) pain - is the most important clue pointing directly to endometriosis, and it's the question likely never asked during your 4 surgeries.

Disclaimer: This is educational information. Please consult a gynecologist with endometriosis expertise for proper evaluation and diagnosis.