Extra Intestinal Manifestations – The Skin

Disclaimer: This information is based on my own research into this particular extra intestinal manifestation of IBD as well as some personal experience and should not be used as medical advice or a diagnostic tool. The suggested investigations and prevalence are part of the IBD protocols set out by NICE; but do vary between CCGs and then thus individual NHS Trusts and specific hospitals.  If you seek advice regarding the things you experience within your own disease, please contact your IBD team for medical advice.

This new series looks at the effects IBD can have beyond the gut. As a whole, extra intestinal manifestations of IBD occur when the disease is not controlled well enough with conventional medications. However, the side effects of particular medications can produce new symptoms which would mirror or mimic these extra intestinal manifestations (EIMs). For all of the information provided in this series, I have gathered resources and broken them down, putting them into patient speak. Each post comes with a disclaimer too (see the end of the post) so if you have concerns, you should see your specialist in all instances. 

The Skin

After arthritis, skin disorders represent the next most common extra intestinal complication of IBD. These affect about 5% of people with inflammatory bowel disease.  It is reported that 22-75% of CD patients and 5-11% of UC patients have skin manifestations, and the proportion will further increase with the extension of the disease. Around 10% of these manifestations are present at the time of IBD diagnosis. However, a great variety of skin lesions may develop during the course of the disease.

The most common skin lesions associated with IBD are Erythema Nodosum (EN), Pyoderma Gangrenosum (PG), and aphthous stomatitis (oral ulceration). As the underlining inflammation of the digestive system goes untreated, or even sub optimally treated, skin issue can develop within this period. However, not all cases of EN or PG will be directly linked from a flare up of IBD; they can occur independently from this; within time of diagnosis, after surgery or even while on particular medications.

This post will look at Erythema Nodosum and Pyoderma Gangernosum.

Who is affected?

Based on their pathophysiological association with the underlying disease (CD or UC), skin manifestations are classified into four categories:

(1) Specific skin manifestations: skin lesion and IBD that have the same microscopic changes. Specific manifestations are basically the same disease as the intestinal disorder just presenting outside of the gastrointestinal tract.

(2) Reactive skin manifestations: Skin lesions and IBD that do not share the same microscopic findings. These are thought to occur as a result of altered immune response to common bacteria on the skin and in the gut. Hence, these are believed to share common mechanisms.

(3) Skin manifestations secondary to malnutrition or malabsorption: skin lesions that occur secondary to deficits in vitamins and trace elements.

(4) Skin manifestations secondary to treatment: these manifestations are a result of immune-mediated adverse reactions to IBD treatment and are direct consequence of the therapies adopted. It is a relatively new phenomenon, which can occur with any type of anti-TNF treatment and is not associated with the underlying IBD activity. Other examples are:

  • Sulfasalazine:  may produce an allergy-type skin rash in some people. The reaction is attributed to the sulfa component of this agent.
  • Steroids: also may cause skin problems when used on a long-term basis. These include stria or stretch marks, thinning of the skin, aggravation of acne, facial puffiness, ankle swelling, and slow wound healing.

EN, the most common cutaneous manifestation of IBD, affects about 3–10% of UC and 4–15% of CD patients. After EN (3–8%), PG represents the second most common cutaneous manifestation of IBD (1–3%), but PG is also the most severe and debilitating. PG is more common in UC (5–12%) than CD (1–2%) and like EN, some studies have shown a female predisposition.


Erythema Nodosum:

  • Painful non-ulcerated nodules on lower extremity
  • Characterised by raised, tender, red, or violet subcutaneous nodules of 1-5 cm in diameter
  • Often associated with systemic symptoms of fevers, chills, arthralgias, or arthritis.
  • Can also be seen in sarcoid, drugs, rheumatologic disease, streptococcal/viral infection
  • Skin lesion reflect that of bowel activity

Pyoderma Gangrenosum:

  • Painful ulceration with purple borders; induced by trauma
  • It can occur anywhere on the body but the common sites are the legs and peristomal sites.
  • Lesions often begin as pustules that rapidly ulcerate and form crater-like holes overlying pus-filled fistulous tracts.
  • May not reflect that of bowel activity


The diagnosis is usually made by a doctor recognising the rounded lumps on the skin on the typical sites. Occasionally it is necessary for a skin biopsy to be done to confirm. This involves the removal of a small sample of skin under local anesthetic, which is then processed by the laboratory and then examined under the microscope. Additional investigations, usually blood tests and a chest x-ray, may be required to determine the underlying cause of EN.

No test can confirm a diagnosis of PG. But a variety of tests will be done to rule out other conditions that may have similar signs or symptoms. These may include blood tests, a skin biopsy and other tests.Your doctor may refer you to a specialist in skin conditions for individual treatment.

Erythema Nodosum

The name literally means “red bumps.” These tender red nodules, which usually appear over the shins or ankles and sometimes on the arms, occur most in people with ulcerative colitis (2%-4%), although they may also affect those with Crohn’s disease of the colon (1%-2%). EN generally appears in conjunction with a flare-up of IBD, but it also may occur just before a flare-up. It tends to improve when the bowel disease is brought under control.

Since EN lesions mirror bowel disease activity and flare up, treatments targeting underlying IBD disease and flare up always leads to the remission of EN. However, in situations where lesions occur during an inactive phase of the disease, low doses of oral steroids can lead to rapid remission of EN  in most cases. Other effective alternatives include NSAIDs, potassium iodide, Colchicine, Dapsone, and immunosuppressants, such as Cyclosporine or Thalidomide. In unmanageable cases, Infliximab has been used with successful results. In general, EN patients have a shorter time to remission (approximately 5 weeks) than do PG patients. However, some patients may experience  new lumps of EN occurring over several weeks, but most patients with EN make a full recovery within a few weeks or months.

Pyoderma Gangernosum

This condition is marked by pus in the skin associated with deep ulcerations.  Beginning as small blisters, these lesions eventually join together to form into deep,chronic ulcers. The disorder is somewhat more common among people with ulcerative colitis (5%) than those with Crohn’s disease (1%).

PG was first described in 1930 by Brunsting as necrotic ulcers containing purulent material (usually sterile on culture) with expanding borders of erythema. The non-infectious pustules and nodules eventually expand outward and develop into painful deep ulcers with undermined wound edges. The ulcer has sharply circumscribed and demarcated borders with a necrotic yellowish base. The ulcers can be single or multiple, unilateral or bilateral, and can range in size from several centimeters to the surface of an entire limb.

PG usually occurs on the extensor surface of the legs, but can appear anywhere on the skin, most noticeably on the abdominal wall adjacent to a post surgical stoma. Peristomal PG lesions occur from 2 weeks to 3 years after ostomy creation and they typically rapidly evolve from small, red pustules to deep ulcers within hours to days.

Compared to EN, PG often takes a more prolonged course and approximately 35% of patients will experience relapse of PG. Diagnosis of PG is usually clinical, but skin biopsy may be necessary for confirmation. PG is classified as a type of neutrophilic dermatosis characterised as skin lesions for which histologic examination reveals intense epidermal, dermal, or hypodermal infiltrates composed primarily of neutrophils with no evidence of infection.

When compared to EN, PG lesions tend to be more severe and resistant to therapy, thus needing more aggressive therapy. About 30% of patients with PG do not experience improvement of their lesions with treatment of the underlying IBD. In general, treatment of PG includes a combination of wound care, topical medications, antibiotics for secondary infections, and treatment targeted at the underlying colitis. Although no individual therapy is universally effective, treatment of PG usually involves a regimen of systemic, topical, and/or intra-lesional medications.

My experience

My diagnosis before Crohn’s Disease was that of Cellulitis, because I presented with some swelling on my elbows and skins. These developed suddenly over a couple of days, leaving me in pain when moving them. They did not get better with antibiotic treatment, and coupled with my vomiting, diarrhea and weight loss, I was then diagnosis with Crohns Disease, along with these lovely raised and red bumps – EN.

My EN would respond to my medication treatments for my IBD but they would become the manifestation that signaled a strong and deep upcoming flare up. In the last seven years, I’ve had three episodes of EN, each time they took weeks to resolve, but only once my bowel was controlled my medication.

Next time… we explore when and how IBD can affect the joints.

Do you have any questions or queries? Or just want to share your own experiences? You can leave me a reply here or leave comments via my social media accounts – on Twitter, find my blog page on Facebook and over on Instagram

Further Reading:

Crohns Colitis Foundation, Dr Kim of UCSD School of Medicine – Extraintestinal Manifestations of IBD 

Crohn’s Colitis Foundation – Skin Complications of IBD

DiscoveryMedicine – Dermatologic Manifestations of Inflammatory Bowel Disease: A Review

NCBI – Frointers in Physiology – Skin Manifestations of Inflammatory Bowel Disease (2012)

NCBI – Pyoderma Gangrenosum Among Patients with Inflammatory Bowel Disease: A Descriptive Cohort Study (October 2014)

British Association of Dermatologists – Erythema Nodosum (doc)

InflammatoryBowelDisease.net – Weird IBD Symptoms: Erythema Nodosum

VeryWellHealth – How Erythema Nodosum is Connected to IBD

Disclaimer: This information is based on my own research into this particular extra intestinal manifestation of IBD as well as some personal experience and should not be used as medical advice. The suggested investigations and prevalence are part of the IBD protocols set out by NICE; but do vary between individual NHS Trusts and specific hospitals.  If you seek advice regarding the things you experience within your own disease,  please contact your IBD team for medical advice.

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