[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Skin](https://durgical.com/en/general-pathology/areas/skin/) › Panniculitis # Panniculitis - Lesion Panniculitis is inflammation of the fat under the skin. It causes tender red lumps, often on the shins. Updated Nov 12, 2026 ## Key points - Erythema nodosum: tender red nodules on the shins, no ulceration, heal without scars; septal panniculitis with Miescher radial granulomas. - Causes of erythema nodosum: streptococcal infection, tuberculosis, sarcoidosis (Löfgren syndrome), inflammatory bowel disease, fungi (histoplasmosis, coccidioidomycosis), drugs (oral contraceptives, sulfonamides), pregnancy, leprosy (erythema nodosum leprosum). - Erythema induratum (nodular vasculitis): calves, ulcerates and scars; lobular panniculitis with vasculitis, caseation; hypersensitivity to Mycobacterium tuberculosis. - Other: lupus panniculitis, pancreatic fat necrosis (ghost adipocytes and calcium), cold panniculitis in infants, traumatic and factitial, alpha-1 antitrypsin deficiency. - Subcutaneous panniculitis-like T-cell lymphoma mimics lobular panniculitis. ## What it is Panniculitis is classified by where the inflammation sits in the subcutaneous fat: in the fibrous septa or in the fat lobules, and whether vasculitis is present. Erythema nodosum, the commonest form, is a septal panniculitis that is a reaction to infections, drugs, sarcoidosis, inflammatory bowel disease and pregnancy. Erythema induratum is a lobular panniculitis with vasculitis, classically linked to tuberculosis. ## Structure - Early erythema nodosum: widened, oedematous septa with neutrophils, lymphocytes and eosinophils. - Later: septal fibrosis, histiocytes and small radial granulomas (Miescher). - Lobular panniculitis: inflammation within lobules with fat necrosis and lipid-laden macrophages. ## Panniculitis by pattern | Disease | Pattern | Clues | | --- | --- | --- | | [Erythema nodosum](https://durgical.com/en/conditions/erythema-nodosum/) | Septal, no vasculitis | Shins, tender, no ulcer; Miescher granulomas | | [Erythema induratum](https://durgical.com/en/conditions/tuberculosis/) | Lobular with vasculitis | Calves, ulcerates; tuberculosis | | [Lupus panniculitis](https://durgical.com/en/conditions/systemic-lupus-erythematosus/) | Lobular, lymphocytic | Hyaline fat necrosis, lymphoid follicles | | [Pancreatic panniculitis](https://durgical.com/en/conditions/acute-pancreatitis/) | Lobular | Ghost adipocytes, saponification, calcium | | [Panniculitis-like T-cell lymphoma](https://durgical.com/en/conditions/non-hodgkin-lymphoma/) | Lobular | Atypical T cells rimming adipocytes | ## Clinical notes - Erythema nodosum prompts a search for streptococcal infection, tuberculosis and sarcoidosis (chest radiograph). - Erythema nodosum leprosum is a type 2 leprosy reaction, relevant in Colombia and Brazil. ## Memory aid Erythema nodosum stays on the fences (septa) and heals clean; erythema induratum invades the fields (lobules), burns vessels and scars. ## Test yourself Think of the answer, then tap the question to see it. ## What type of panniculitis is erythema nodosum? A septal panniculitis without vasculitis. ## Which infection is classically linked to erythema induratum? Tuberculosis (a hypersensitivity response to Mycobacterium tuberculosis antigens). ## What are three causes of erythema nodosum? Streptococcal infection, sarcoidosis and inflammatory bowel disease (also tuberculosis, fungi, drugs, pregnancy). [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/general-pathology/panniculitis/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Elsewhere in DurgiPedia - [Granulomatous inflammation: caseating vs non-caseating, the causes to know](https://durgical.com/en/general-pathology/granulomatous-inflammation-caseating-vs-non-caseating-the-causes-to-know/) - [Patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous](https://durgical.com/en/general-pathology/patterns-of-necrosis-coagulative-liquefactive-caseous-fat-fibrinoid-gangrenous/) - [Adipose tissue: white and brown fat](https://durgical.com/en/histology/adipose-tissue-white-and-brown-fat/) ## Connections ## Related 4 - [Skin pathology: terms and reaction patterns](https://durgical.com/en/general-pathology/skin-pathology-terms-and-reaction-patterns/) - [Acute pancreatitis: morphology and complications](https://durgical.com/en/general-pathology/acute-pancreatitis-morphology-and-complications/) - [Patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous](https://durgical.com/en/general-pathology/patterns-of-necrosis-coagulative-liquefactive-caseous-fat-fibrinoid-gangrenous/) - [Granulomatous inflammation: caseating vs non-caseating, the causes to know](https://durgical.com/en/general-pathology/granulomatous-inflammation-caseating-vs-non-caseating-the-causes-to-know/) ## Related conditions 7 - [Erythema nodosum](https://durgical.com/en/conditions/erythema-nodosum/) - [Tuberculosis](https://durgical.com/en/conditions/tuberculosis/) - [Sarcoidosis](https://durgical.com/en/conditions/sarcoidosis/) - [Acute pancreatitis](https://durgical.com/en/conditions/acute-pancreatitis/) - [Systemic lupus erythematosus](https://durgical.com/en/conditions/systemic-lupus-erythematosus/) - [Crohn disease](https://durgical.com/en/conditions/crohn-disease/) - [Ulcerative colitis](https://durgical.com/en/conditions/ulcerative-colitis/) [← All of general pathology](https://durgical.com/en/general-pathology/) Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Skin Conditions](https://medlineplus.gov/skinconditions.html) (MedlinePlus, US National Library of Medicine, 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/panniculitis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/panniculitis/