Skin: Erythema Nodosum, Pyoderma Gangrenosum

Erythema nodosum and pyoderma gangrenosum are important skin conditions linked to inflammatory bowel disease. Erythema nodosum often appears during active gut inflammation and usually settles when IBD is controlled. Pyoderma gangrenosum is rarer, very painful, and can progress quickly. It needs prompt, coordinated care with dermatology and gastroenterology. Recognizing both early helps prevent scarring, infection, and avoidable surgery. (academic.oup.com)

Key takeaways

• Erythema nodosum often tracks IBD activity and improves as gut inflammation is treated. (academic.oup.com)

• Pyoderma gangrenosum may not mirror gut activity, can follow minor trauma, and needs urgent specialist care. (link.springer.com)

• For pyoderma gangrenosum, avoid wide surgical debridement during the active phase. Use careful wound care. (dermnetnz.org)

• First-line systemic options for pyoderma gangrenosum include corticosteroids, ciclosporin, and anti‑TNF therapy, with RCT evidence for infliximab. (pubmed.ncbi.nlm.nih.gov)

• Routine NSAIDs can aggravate IBD in some people. Discuss safer pain options. (journals.lww.com)

What they are

• Erythema nodosum (EN) presents as tender, red to violet bumps under the skin, usually on the shins. It is the most common skin manifestation in IBD. Reported in up to 15% of people with Crohn’s and 3 to 10% with ulcerative colitis. (academic.oup.com)

• Pyoderma gangrenosum (PG) is a neutrophilic skin disease. It often starts as a pustule or red plaque, then breaks down into a deep, very painful ulcer with undermined purple borders. It affects about 0.4% to 2.6% of people with IBD. (academic.oup.com)

Why they happen and how they relate to gut disease

EN is a reactive process that commonly flares with intestinal inflammation. Controlling gut disease is the main treatment, and the nodules usually resolve as inflammation settles. (academic.oup.com)

PG can appear during active IBD, when IBD is quiet, or even precede diagnosis. Minor skin injury can trigger lesions, a phenomenon called pathergy. (link.springer.com)

Diagnosis at a glance

• EN is usually a clinical diagnosis. Doctors may check blood work, chest imaging, and throat or stool tests to look for other triggers. Biopsy is rarely needed. (dermnetnz.org)

• PG is a clinical diagnosis supported by biopsy to exclude infection and vasculitis. The 2018 Delphi criteria aid diagnosis. Cultures help rule out secondary infection. (dermnetnz.org)

First steps in management

• Involve dermatology early for both conditions. Coordinate care with the IBD team. (academic.oup.com)

• Review medicines and infections. Exclude mimics before starting strong immunosuppression. (dermnetnz.org)

Erythema nodosum: treatment options

• Treat the underlying IBD. Lesions usually fade over days to weeks as gut inflammation improves. (academic.oup.com)

• Supportive care can include rest, leg elevation, and compression if tolerated. Colchicine is sometimes used. (dermnetnz.org)

• Short courses of systemic corticosteroids may be considered for severe pain or swelling after infection is excluded. (dermnetnz.org)

• Routine NSAID use can worsen IBD in some patients, so pain control should favor alternatives, and any NSAID trial should be individualized. (journals.lww.com)

Pyoderma gangrenosum: treatment options

• Wound care: use non‑adhesive, moisture‑balancing dressings. Treat secondary infection if present. Compression can help leg edema. Avoid wide surgical debridement during the active inflammatory phase because of pathergy. Gentle, conservative removal of nonviable tissue may be considered by experienced teams. (dermnetnz.org)

• Topical therapy for small ulcers: high‑potency topical corticosteroids, topical tacrolimus, or intralesional steroid at the ulcer edge. (dermnetnz.org)

• Systemic therapy for moderate to severe disease:

• Corticosteroids, often started first for rapid control. (academic.oup.com)

• Ciclosporin, comparable to prednisolone in a head‑to‑head randomized trial. Choice depends on side effects and patient preference. (pubmed.ncbi.nlm.nih.gov)

• Anti‑TNF therapy, especially infliximab, with randomized trial evidence of early benefit. (pubmed.ncbi.nlm.nih.gov)

• Other options in selected cases include ustekinumab or dapsone, guided by specialist input. (academic.oup.com)

Special situations

• Peristomal PG can occur around an ostomy. It is often misdiagnosed as infection or irritation. Medical therapy plus meticulous stoma care is preferred. Stoma relocation alone does not solve active PG. Involve a stoma nurse early. (jamanetwork.com)

When to seek urgent care

• Rapidly expanding, very painful ulcers.

• Fever, spreading redness, or drainage suggesting infection.

• Severe leg pain or swelling with EN, especially if unable to walk.
  Prompt evaluation helps prevent scarring and complications. (msdmanuals.com)

EN vs PG at a glance

Sources: ECCO EIM guideline, DermNet, RCTs. (academic.oup.com)

FAQs

Can these skin problems happen when the gut is quiet

Erythema nodosum usually follows intestinal activity. Pyoderma gangrenosum can occur with active or inactive IBD, and may follow minor trauma. (academic.oup.com)

Should a PG ulcer be debrided or grafted

Avoid wide or aggressive debridement during active disease due to pathergy. Conservative debridement may be reasonable in expert hands, and grafting is considered after inflammation is controlled. (dermnetnz.org)

Do antibiotics cure PG

No. Bacteria in the wound are usually secondary. Treat infection when present, but immunosuppression and wound care are the main treatments. (dermnetnz.org)

Are NSAIDs safe for EN pain in someone with IBD

NSAIDs can trigger flares in some people with IBD. Discuss alternatives like acetaminophen or short supervised use with the care team. (journals.lww.com)