Pyoderma Gangrenosum vs Erythema Nodosum: Know the Differences

Pyoderma Gangrenosum vs Erythema Nodosum

Pyoderma Gangrenosum vs Erythema Nodosum: Pyoderma Gangrenosum and Erythema Nodosum are distinct inflammatory skin conditions often associated with underlying systemic diseases. Pyoderma Gangrenosum is characterized by painful ulcers that spread quickly. Usually, these ulcers begin as pustules or nodules and grow into huge, uneven ulcers, usually on the legs. Erythema Nodosum, on the other hand, manifests as red, sensitive nodules on the shins that do not ulcerate. Erythema Nodosum is connected to infections, autoimmune illnesses, and drugs, whereas Pyoderma Gangrenosum is linked to ailments like rheumatoid arthritis and inflammatory bowel disease. For the right course of treatment, an accurate diagnosis is essential. 

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Difference between Pyoderma Gangrenosum and Erythema Nodosum 

Pyoderma Gangrenosum are painful ulcers associated with inflammation, usually on the legs. Tender red nodules, usually on the shins, associated with autoimmune disorders or infections are called Erythema Nodosum. Treatments differ; immunosuppression may be necessary for Pyoderma Gangrenosum, whilst rest and medicine are usually sufficient for Erythema Nodosum. The table below provides the differences between Pyoderma Gangrenosum and Erythema Nodosum.


Pyoderma Gangrenosum

Erythema Nodosum


Painful ulcers with undermined borders

Tender, red nodules on shins


Rapidly progressing, can lead to large ulcers

Lesions do not ulcerate or progress


Commonly on legs, but can occur anywhere

Typically on shins, but can occur elsewhere

Systemic associations

Associated with inflammatory bowel disease, rheumatoid arthritis, and hematologic disorders

Associated with infections (e.g., streptococcal infections, tuberculosis), autoimmune diseases (e.g., sarcoidosis, inflammatory bowel disease), and medications


Management focuses on underlying condition, often involves immunosuppressive therapy

Addressing underlying cause, rest, and symptomatic relief; may include nonsteroidal anti-inflammatory drugs (NSAIDs) or corticosteroids


Variable depending on underlying condition

Generally resolves with treatment of underlying cause; may recur

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What is Pyoderma Gangrenosum?

Pyoderma Gangrenosum is a rare inflammatory skin condition that causes painful ulcers that spread quickly. Usually starting as little pustules or nodules, these ulcers rapidly grow into big, unevenly shaped lesions with weak margins. Though they usually appear on the legs, they can appear elsewhere on the body. Pyoderma Gangrenosum is frequently linked to underlying systemic conditions such as rheumatoid arthritis, inflammatory bowel illness, or hematologic abnormalities. The clinical presentation is used to make the diagnosis, and other potential causes of skin ulcers are ruled out. The course of treatment often entails treating the underlying ailment, which may need immunosuppressive medication.

Causes of Pyoderma Gangrenosum

  • Immune System Dysfunction: Pyoderma Gangrenosum is classified as an autoimmune disease, meaning that tissue damage and inflammation result from the immune system unintentionally attacking its tissues.
  • Genetic Predisposition: Although it is uncommon, Pyoderma Gangrenosum may be inherited. There may be a genetic component to certain cases, as several reports of cases occurring in families have indicated.
  • Underlying Systemic Diseases: Pyoderma Gangrenosum may be associated with inflammatory bowel disease (such as Crohn's disease or ulcerative colitis), rheumatoid arthritis, autoimmune hepatitis, and hematologic disorders such as myeloproliferative disorders.
  • Trauma or Injury: Surgical wounds, slashes, or burns are examples of trauma locations where Pyoderma Gangrenosum may occasionally develop. It's crucial to remember, though, that Pyoderma Gangrenosum can also develop on its own without any prior trauma.
  • Infection: Although not the primary cause, infections may intensify or precipitate lesions of Pyoderma Gangrenosum. Sometimes the onset of Pyoderma Gangrenosum is preceded by viral or bacterial infections.

Symptoms of Pyoderma Gangrenosum

  • Ulceration: The formation of skin ulcers is the primary sign of Pyoderma Gangrenosum. Usually, these ulcers start as tiny, painful papules or pustules that spread quickly to become painful, deep ulcers with weak borders. The edges of the ulcers may be characterized by a distinctive purple or blue tint.
  • Pain: People who have Pyoderma Gangrenosum ulcers frequently report excruciating pain that feels like a burning or stinging sensation. If there is a lot of pressure or motion where the ulcers reside, the pain could be excruciating and incapacitating.
  • Rapid Progression: Pyoderma Gangrenosum lesions can grow larger and more deeply throughout a short amount of time, often in just a few hours or days. 
  • Undermined Borders: The skin surrounding Pyoderma Gangrenosum ulcers usually looks to be eroded or undermined, giving the ulcers a distinctive punched-out appearance.
  • Size and Shape: Pyoderma Gangrenosum ulcers can vary in size and shape, ranging from small, round lesions to larger, irregularly shaped ulcers. Though they most frequently affect the legs, they can affect any area of the body and manifest as a single lesion or many lesions.

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What is Erythema Nodosum?

Erythema Nodosum is a skin inflammatory condition that causes red, painful nodules or bumps on the shins. It is thought to be a kind of panniculitis, which is characterized by skin inflammation in the fatty layer. Erythema Nodosum may manifest as a single ailment or as a sign of a more serious systemic illness. Erythema Nodosum nodules might appear "bruised" and are typically red or reddish-purple. They feel warm to the touch and are frequently firm. These lesions may cause pain or discomfort, especially when pressure is applied, and are frequently tender to the touch. 

Causes of Erythema Nodosum

  • Infections: Viral, fungal, bacterial, or parasitic infections can cause Erythema Nodosum. A prominent cause of infection is streptococcal infections, such as strep throat. Histoplasmosis, coccidioidomycosis, TB, and infectious mononucleosis are a few more infectious reasons that could exist.
  • Systemic Disorders: Inflammatory bowel disease (IBD) and autoimmune diseases are two examples of underlying systemic conditions that are frequently linked to Erythema Nodosum. Erythema Nodosum is frequently associated with conditions such as sarcoidosis, Behçet's disease, Crohn's disease, and ulcerative colitis.
  • Medication: It has been noted that Erythema Nodosum can occur as a side effect of some drugs. These might include oral contraceptives, nonsteroidal anti-inflammatory medications (NSAIDs), antibiotics (such as penicillins and sulfonamides), and certain anticonvulsants.\
  • Pregnancy: While the precise etiology of Erythema Nodosum is unknown, it can happen during pregnancy. It can be connected to the immune system or hormone changes that occur during pregnancy.
  • Malignancies: Erythema Nodosum can occasionally coexist with various malignancies, including solid tumors, lymphomas, and leukemia. This relationship is very uncommon, though.
  • Environmental Factors: In susceptible individuals, exposure to specific environmental conditions, such as cold temperatures, may cause or worsen Erythema Nodosum.

Symptoms of Erythema Nodosum

  • Red, Tender Nodules: The emergence of red, painful nodules or bumps under the skin, usually on the shins but occasionally on other parts of the body like the thighs, arms, or trunk, is the classic symptom of Erythema Nodosum.
  • Warmth and Tenderness: The afflicted areas may be uncomfortable or tender to the touch, particularly under pressure.
  • Swelling: In the regions impacted by the nodules, swelling may also be present.
  • Skin Discoloration: A reddish or purple tint may appear on the skin surrounding the nodules.
  • Joint Pain: In certain instances, joint pain, especially in the ankles, knees, wrists, and elbows, may also arise.

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Similarities between Pyoderma Gangrenosum and Erythema Nodosum

  • Inflammatory Nature: Skin disorders that cause inflammation include Erythema Nodosum and Pyoderma Gangrenosum. They cause skin inflammation, which manifests as symptoms.
  • Related Conditions: There may be underlying systemic diseases connected to both conditions. Rheumatoid arthritis, various autoimmune diseases, and inflammatory bowel diseases are frequently linked to Pyoderma Gangrenosum. such as sarcoidosis, inflammatory bowel disease, infections, and some drugs can also be linked to Erythema Nodosum.
  • Potential Overlap: Patients may experience Erythema Nodosum and Pyoderma Gangrenosum concurrently or one after the other. This implies that certain people have predisposing factors or a common underlying mechanism.
  • Diagnosis: Based on clinical appearance and occasionally bolstered by skin biopsy, Pyoderma Gangrenosum and Erythema Nodosum are both diagnosed. However, making a diagnosis frequently entails eliminating alternative possible explanations for comparable skin symptoms.

In summary, Erythema Nodosum and Pyoderma Gangrenosum are inflammatory skin disorders, but they differ in terms of their underlying causes, clinical presentations, and rates of progression. To properly manage and treat those who are impacted, healthcare professionals must be able to distinguish between the two.

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What are Pyoderma Gangrenosum and Erythema Nodosum?

While both Pyoderma Gangrenosum (PG) and Erythema Nodosum (EN) are inflammatory skin disorders, there are clear distinctions between the two in terms of appearance and underlying causes.

How do the skin lesions appear in Pyoderma Gangrenosum and Erythema Nodosum?

The characteristic presentation of skin lesions in Pyoderma Gangrenosum is deep, painful ulcers with weakened margins. Conversely, Erythema Nodosum appears as red, sensitive pimples or nodules beneath the skin, usually on the shins.

What causes Pyoderma Gangrenosum and Erythema Nodosum?

Pyoderma Gangrenosum is frequently linked to underlying systemic illnesses such as rheumatoid arthritis, ulcerative colitis, Crohn's disease, and other autoimmune disorders. Additionally, systemic conditions such as sarcoidosis, infections, inflammatory bowel disease, or specific drugs may be linked to Erythema Nodosum.

Which condition is more painful, Erythema Nodosum or Pyoderma Gangrenosum?

Erythema Nodosum nodules can be tender to the touch but usually cause less pain than Pyoderma Gangrenosum ulcers, which are often excruciatingly painful.

What are the differences between Pyoderma Gangrenosum and Erythema Nodosum?

Erythema Nodosum appears as red, tender nodules or pimples under the skin, while Pyoderma Gangrenosum causes deep, painful ulcers with weakened edges.