Skin: Erythema Nodosum, Pyoderma Gangrenosum

Erythema nodosum and pyoderma gangrenosum are two important skin conditions that can occur with inflammatory bowel disease (IBD). They cause painful nodules or ulcers that can limit walking, sleep, and daily activities. These skin changes sometimes track with gut inflammation and sometimes act more independently. Recognizing their typical appearance and understanding treatment options helps the care team protect both skin and overall IBD control.

Key takeaways

• Erythema nodosum (EN) causes tender red or purple lumps, usually on the shins, and is the most common IBD‑related skin problem. (academic.oup.com)

• EN often appears during active Crohn’s disease or ulcerative colitis and usually improves once the intestinal flare is controlled. (academic.oup.com)

• Pyoderma gangrenosum (PG) causes very painful ulcers with purple edges, often on the legs or around a stoma, and is less common but more disabling. (academic.oup.com)

• PG may not always follow gut activity and usually needs early specialist care, including wound care and systemic medicines such as steroids or biologics. (academic.oup.com)

• For both EN and PG, treatment focuses on controlling IBD, ruling out infection, easing pain, and using skin‑directed therapies when needed. (academic.oup.com)

• Rapidly spreading ulcers, signs of infection, or severe pain are red flags that should prompt urgent medical attention. (academic.oup.com)

How these skin conditions fit into IBD

Erythema nodosum and pyoderma gangrenosum are considered “reactive” cutaneous extraintestinal manifestations (EIMs). That means the same overactive immune system that drives IBD also inflames the skin, even though the skin lesions do not contain bowel tissue. (academic.oup.com)

Skin EIMs are common in IBD. Overall, about 15 to 20 percent of people with IBD develop some form of skin involvement, and EN and PG are among the best recognized. (academic.oup.com)

• Erythema nodosum is the most frequent cutaneous EIM, affecting roughly 3 to 15 percent of people with Crohn’s disease or ulcerative colitis. (academic.oup.com)

• Pyoderma gangrenosum is less common, affecting well under 3 percent, but is often more severe and painful. (academic.oup.com)

Both can appear before, during, or after an IBD diagnosis, and in some people they are an early clue that leads to testing for IBD. (pubmed.ncbi.nlm.nih.gov)

Erythema nodosum in IBD

What erythema nodosum looks and feels like

Erythema nodosum is an inflammation of the fat layer under the skin. It causes: (dermnetnz.org)

• Painful, firm, red or violet bumps or plaques

• Usually 1 to 5 cm in size

• Most often on the fronts of the shins, sometimes on thighs or forearms

• Warm and tender to the touch

• Color changes over time from bright red to bruised‑looking, then yellow‑green as they heal

Systemic symptoms like fatigue, low‑grade fever, and ankle joint pain are common. (dermnetnz.org)

Link with IBD activity

In IBD, EN is strongly associated with active intestinal inflammation. It often appears or worsens with flares and tends to fade as gut disease comes under control. (academic.oup.com)

Other potential triggers should still be checked, including: infections, medicines, pregnancy, and other inflammatory conditions such as sarcoidosis. (dermnetnz.org)

Diagnosis

Diagnosis is usually based on the typical appearance and distribution of the nodules plus the IBD history. Skin biopsy is not always required but may be used if the picture is unclear or another diagnosis is possible. (academic.oup.com)

Clinicians also review recent infections, new medications, and blood tests to look for other causes.

Treatment and self‑care

Management focuses on both the underlying IBD and local symptom relief. (academic.oup.com)

Common elements include:

• Optimize IBD control

• Adjusting IBD therapy to control the flare often leads to gradual clearing of EN. (academic.oup.com)

• Supportive measures

• Relative rest and leg elevation

• Compression stockings or wraps when appropriate

• Cool packs or gentle emollients to ease discomfort (dermatologyadvisor.com)

• Pain control

• Acetaminophen is often preferred for people with IBD.

• Nonsteroidal anti‑inflammatory drugs (NSAIDs) can be effective for EN pain, but many gastroenterology guidelines advise limiting long‑term or high‑dose NSAIDs in IBD because of possible gut irritation, especially in active disease. (pubmed.ncbi.nlm.nih.gov)

• Skin‑directed and systemic therapies for more severe EN

• Topical corticosteroid creams over painful nodules

• Short courses of systemic corticosteroids when lesions are very painful or widespread

• Other options in selected cases, such as potassium iodide or dapsone, usually under dermatology guidance (academic.oup.com)

EN usually resolves over several weeks, often without scarring, though temporary skin color changes can persist for some time. (dermnetnz.org)

Pyoderma gangrenosum in IBD

What pyoderma gangrenosum looks and feels like

Pyoderma gangrenosum is a neutrophilic dermatosis, a condition in which certain white blood cells overreact in the skin and create intense inflammation. It typically presents as: (academic.oup.com)

• A small pustule or red bump that quickly breaks down

• Expansion into a deep, extremely painful ulcer

• Undermined edges with a purple or dark rim

• A base that looks purulent but is usually sterile on culture

Lesions often occur on the lower legs or around ostomies (peristomal PG), but they can appear almost anywhere. Mild trauma, such as a needle stick or friction from clothing, can trigger new lesions, a feature called pathergy. (academic.oup.com)

Relationship to gut disease

PG is the second most common reactive skin EIM in IBD and is particularly linked with ulcerative colitis, though it also occurs in Crohn’s disease. (academic.oup.com)

Unlike EN, PG does not always track with gut activity. Some people develop PG while their bowel disease is relatively quiet, while others see it worsen during flares. (pubmed.ncbi.nlm.nih.gov)

Diagnosis

There is no single test for PG. Diagnosis relies on: (academic.oup.com)

• Clinical appearance and rapid ulcer progression

• Excluding infection, vascular disease, and other causes of ulcers

• Often a skin biopsy to rule out alternatives and support the diagnosis

Because misdiagnosis is common, early referral to a dermatologist familiar with PG is recommended.

Treatment approach

PG is painful and potentially destructive, so management is usually aggressive and multidisciplinary, often involving dermatology, gastroenterology, wound care, and sometimes surgery teams. (academic.oup.com)

Key components:

• Supportive wound and pain care

• Non‑adherent dressings, moist wound environment, and protection from trauma

• Adequate pain management, which may require more than simple over‑the‑counter options (academic.oup.com)

• Topical and local therapy for mild or localized PG

• Super‑potent topical corticosteroid ointments or creams

• Topical calcineurin inhibitors such as tacrolimus

• Occasional intralesional steroid injections in carefully selected settings, often around stomas (academic.oup.com)

• Systemic therapy for moderate to severe PG

• Systemic corticosteroids are often used early to control inflammation

• Calcineurin inhibitors such as cyclosporine are established options in severe disease

• Biologic therapy, particularly anti‑TNF agents like infliximab or adalimumab, has shown high response and healing rates in IBD‑associated PG and is now a cornerstone of treatment in many guidelines (academic.oup.com)

• Other agents used in refractory cases can include ustekinumab, mycophenolate mofetil, and sometimes JAK inhibitors such as tofacitinib. (academic.oup.com)

• IBD control

• Because systemic agents for PG often overlap with advanced IBD therapies, treatment plans are usually coordinated so that one regimen addresses both gut and skin disease whenever possible. (academic.oup.com)

Surgery is generally avoided directly through active PG ulcers because trauma can worsen the condition, but surgical revision or closure of a stoma can help some people with persistent peristomal PG. (academic.oup.com)

Erythema nodosum vs pyoderma gangrenosum at a glance

(academic.oup.com)

Practical tips for managing skin EIMs

• Early reporting and photos
  New nodules or ulcers should be documented and brought to the attention of the IBD team promptly. Photos over time can help track response to treatment.

• Coordinate care
  Dermatology involvement is recommended for EN that is atypical or persistent and almost always for PG. Joint planning between dermatology and gastroenterology helps align systemic treatments. (academic.oup.com)

• Medication review
  Potential triggers such as certain antibiotics, oral contraceptives, or other drugs should be reviewed when EN appears. (dermnetnz.org)

• Mental health and quality of life
  Visible skin disease and chronic ulcers can be distressing and limiting. Psychological support, pain services, and social work can be valuable parts of care. (pubmed.ncbi.nlm.nih.gov)

When it may be urgent

People with IBD and known or suspected EN or PG should seek urgent medical evaluation if they develop:

• Rapidly enlarging or spreading ulcers

• High fever, chills, or feeling very unwell

• Spreading redness, foul odor, or drainage that suggests infection

• Severe uncontrolled pain or difficulty walking or using the affected limb (academic.oup.com)

FAQs

Can erythema nodosum or pyoderma gangrenosum appear before IBD is diagnosed?

Yes. In some people, EN or PG appears months or years before bowel symptoms are recognized, and their evaluation leads to an eventual IBD diagnosis. (pubmed.ncbi.nlm.nih.gov)

Do these skin conditions mean IBD is getting worse?

Erythema nodosum often signals active gut inflammation, so it can be a marker that IBD needs reassessment. Pyoderma gangrenosum does not always parallel gut activity, but its presence usually prompts a careful review of overall disease control and treatment options. (academic.oup.com)

Do EN or PG increase the risk of skin cancer?

They do not by themselves appear to raise skin cancer risk. However, some treatments used for IBD and for these skin EIMs, such as thiopurines or long‑term immunosuppression, can modestly increase certain skin cancer risks, so routine sun protection and dermatologic skin checks are often advised. (academic.oup.com)

Will pyoderma gangrenosum ulcers ever heal?

With modern immunosuppressive and biologic therapies, many people with IBD‑associated PG achieve complete or near‑complete healing, although this can take weeks to months and often leaves scars. Early recognition, coordinated specialist care, and good wound management improve the chances of healing. (academic.oup.com)