Your HS Is More Than a Lesion Count: The Six Things That Actually Matter

Two people both have an IHS4 scoreIHS4 Score: A validated, dynamic tool for measuring current inflammatory disease activity in Acne Inversa (unlike the mainly structural, static Hurley stage). The score is calculated from the number of inflammatory nodules, plus 2 points per abscess, plus 4 points per draining sinus tract; scores up to 3 are mild, 4–10 moderate, 11 or more severe. This allows objective tracking of treatment response over time.IHS4 ScoreA validated, dynamic tool for measuring current inflammatory disease activity in Acne Inversa (unlike the mainly structural, static Hurley stage). The score is calculated from the number of inflammatory nodules, plus 2 points per abscess, plus 4 points per draining sinus tract; scores up to 3 are mild, 4–10 moderate, 11 or more severe. This allows objective tracking of treatment response over time.Read more in the glossary of 6. One sleeps badly, can barely sit comfortably, has daily drainage, and has stopped exercising. The other has well-controlled pain and works normally. The number is identical. The disease burden isn’t.

That isn’t a flaw in the IHS4 score — the companion article on Hurley stages and IHS4 explains that IHS4 is deliberately, and well-validatedly, a measure of current inflammatory activity: nodulesNodule: A firm, palpable lump deep in tissue. Nodules can be painful and may progress to abscesses. They are among the typical early signs of Acne Inversa.NoduleA firm, palpable lump deep in tissue. Nodules can be painful and may progress to abscesses. They are among the typical early signs of Acne Inversa.Read more in the glossary, abscessesAbscess: An inflamed cavity or swelling containing pus or fluid. In hidradenitis suppurativa, abscesses can form as part of the inflammatory disease process and do not automatically mean that a bacterial infection is present. Secondary bacterial infection can occur and may require separate medical assessment. In Acne Inversa, abscesses occur mainly in the armpits, groin, and other skin folds.AbscessAn inflamed cavity or swelling containing pus or fluid. In hidradenitis suppurativa, abscesses can form as part of the inflammatory disease process and do not automatically mean that a bacterial infection is present. Secondary bacterial infection can occur and may require separate medical assessment. In Acne Inversa, abscesses occur mainly in the armpits, groin, and other skin folds.Read more in the glossary and draining tunnelsDraining Tunnel: A sinus tract or fistula actively leaking fluid (serous, purulent, or blood-tinged) to the surface. Draining tunnels carry the heaviest weight in modern HS severity scores because they signal long-standing, structurally damaged disease.Draining TunnelA sinus tract or fistula actively leaking fluid (serous, purulent, or blood-tinged) to the surface. Draining tunnels carry the heaviest weight in modern HS severity scores because they signal long-standing, structurally damaged disease.Read more in the glossary. The mistake is confusing one number with the whole disease. That is exactly the problem an international consensus process called HISTORIC set out to address — with a result broader than just “a better score.”

This article explains which six domains that consensus identified as important, why one of them proved more contested than the others, and what this practically means for how you track your own HS and how you talk about it at appointments.

For information only. This article explains an international consensus process on outcome measurement in HS research. It does not diagnose anything and does not replace an individual clinical assessment of your severity.

Key takeaways

• A single severity score like IHS4 measures one specific thing well — current inflammatory activity — but not your whole disease.
• An international consensus process (HISTORIC) used a Delphi process to set five jointly-agreed core domains: pain, physical signs, HS-specific quality of life, global assessment and disease course.
• A sixth domain — symptoms beyond pain — was especially strongly prioritised by patients and recommended for the core list.
• The new European guideline (2026) explicitly refers to this broader framework.
• Knowing which question a number answers makes an appointment more targeted than just going by the score.

Who HISTORIC is and what the consensus process set out

HISTORIC (the HIdradenitis SuppuraTiva cORe outcomes set International Collaboration) is an international group of patients, dermatologists, surgeons, and industry and regulatory representatives. Their aim was to use a Delphi process — several anonymous online survey rounds plus in-person consensus meetings on two continents — to agree on what every clinical HS trial should, at minimum, measure and report.

The background: before this consensus, HS trials used a wide range of different measurement instruments. That made comparing results across studies substantially harder and encouraged selective outcome reporting — a study could focus on whichever measures happened to look best, rather than a shared, agreed set.

The outcome of the process: five domains that patients and healthcare professionals agreed on together, plus a sixth domain that was especially strongly supported by patients specifically.

The six domains

1. Pain. For many people with HS, the single most burdensome symptom. Follow-up work within HISTORIC has focused specifically on how pain should be measured consistently — for example, over what recall window (pain in the last 24 hours, say) and whether maximum or average pain is captured, since earlier studies varied widely on this.

2. Physical signs. What an examination can see or measure directly — nodules, abscesses, draining tunnelsSinus Tract: A tunnel-like channel under the skin that forms between abscesses or nodules. Sinus tracts indicate more advanced disease and can chronically drain fluid. They are associated with Hurley Stages II and III.Sinus TractA tunnel-like channel under the skin that forms between abscesses or nodules. Sinus tracts indicate more advanced disease and can chronically drain fluid. They are associated with Hurley Stages II and III.Read more in the glossary. IHS4 is one example of an instrument that covers this domain.

3. HS-specific quality of life. A dedicated validated instrument was developed for this, the HiSQOLHiSQoL (Hidradenitis Suppurativa Quality of Life): A 17-item HS-specific quality-of-life questionnaire validated in the late 2010s. More sensitive to HS-specific concerns (drainage, odour, intimacy) than the general DLQI.HiSQoL (Hidradenitis Suppurativa Quality of Life)A 17-item HS-specific quality-of-life questionnaire validated in the late 2010s. More sensitive to HS-specific concerns (drainage, odour, intimacy) than the general DLQI.Read more in the glossary (Hidradenitis Suppurativa Quality of Life score), which captures how the condition affects daily activities, clothing choices, intimacy, mood and social situations.

4. Global assessment. An overall judgement — from a clinician, or from you — of how the disease is doing overall, which doesn’t fully replace any of the other domains but adds context to them.

5. Disease course. How the condition develops over time — stable, worsening or improving — independent of any single current value.

6. Symptoms beyond pain. Anything you feel or notice that isn’t already covered by pain or physical signs. This domain was especially strongly supported by the patients involved, less strongly by healthcare professionals during the consensus process, and is therefore described as a recommended rather than a fully uncontested part of the core set. Two concrete examples many people with HS describe as burdensome in their own right, and that this blog already covers in detail: drainage and odour and sleep and fatigue.

Why the sixth domain was more contested

That patients and healthcare professionals agreed to different degrees on this domain is itself revealing. It reflects a real, often unspoken difference in perspective: an examination is good at capturing what’s visible — lesions, tunnels, scars. What drainage means for daily life, how much fatigue limits the ability to function normally, or how socially burdensome worries about odour can be, is much harder to capture in a short examination — but no less real to live with.

That isn’t a criticism of clinicians. It’s a reason to raise these symptoms explicitly in an appointment, rather than trusting they’ll automatically be accounted for when the conversation is about lesions.

What the new guideline says about this

The new European S2k guideline (Part 1, 2026) explicitly refers to this broader framework for severity and outcome measurement, rather than reducing severity to a single score alone. That’s consistent with the general direction of this guideline update: a more comprehensive, multidimensional view of the disease that goes beyond a lesion count alone — the same underlying idea that also drives its expanded chapter on comorbiditiesComorbidity: An additional condition existing alongside the primary disease. Acne Inversa is frequently associated with comorbidities including metabolic syndrome, inflammatory bowel disease, spondyloarthritis, and depression.ComorbidityAn additional condition existing alongside the primary disease. Acne Inversa is frequently associated with comorbidities including metabolic syndrome, inflammatory bowel disease, spondyloarthritis, and depression.Read more in the glossary and screening.

What this practically means for you

You don’t need to know the consensus process in detail to benefit from it. Two practical consequences:

For your own tracking. If you only count lesions or note a single pain score, you may be missing half the picture. Drainage, sleep quality, fatigue, and how the condition affects specific daily activities are just as much part of your disease as the number of nodules.

For your appointments. If a visit focuses exclusively on lesion count or IHS4, it’s legitimate to explicitly add what else has changed — for example: “The score may have improved, but my fatigue and drainage are still a real burden.” That isn’t a contradiction of the finding; it’s additional, equally relevant information.

What the evidence does not show

Current evidence does not show that:

• a single score — IHS4, Hurley, or any other — on its own captures a person’s entire disease burden;
• all six domains are already measured consistently with validated instruments in routine care — for some, especially symptoms beyond pain, standardisation isn’t finished yet;
• an improvement in one domain automatically means improvement in another.

The bottom line

An IHS4 score of 6 is real, useful information — but it answers one specific question, not every question that matters about your disease. The international HISTORIC consensus set out six domains that together give a fuller picture: pain, physical signs, quality of life, global assessment, disease course — and the symptoms beyond pain that patients themselves raise most strongly. None of these domains replaces the others. Together, they describe something a single number never could.