Panniculitis: 10 Clinical Types, Causes And Treatment
Inflammation of subcutaneous fat causing tender nodules: causes, diagnosis, and treatment options explored.
Panniculitis refers to a diverse group of conditions characterised by inflammation of the subcutaneous fat (panniculus adiposus). Despite varied aetiologies, most forms share a similar clinical presentation of tender, erythematous or bruised subcutaneous nodules, most often on the lower legs. Associated symptoms such as fever, malaise, and arthralgia are common. Diagnosis relies on clinical features combined with skin biopsy, which reveals characteristic histopathological patterns depending on the underlying cause. The most prevalent type is
erythema nodosum
. This article explores the clinical features, classification, causes, investigations, and management of panniculitis.Who gets panniculitis?
Panniculitis can affect individuals of any age but is more common in adults, particularly women for certain subtypes like erythema nodosum. It occurs worldwide without strong racial predilection. Predisposing factors include:
- Young to middle-aged adults (20–45 years for erythema nodosum)
- Female predominance in septal panniculitides
- Children and infants for cold-related forms
- Immunocompromised states for infectious causes
- Systemic diseases such as infections, autoimmune disorders, or malignancies
Risk increases with triggers like streptococcal infections, oral contraceptives, or pregnancy for erythema nodosum.
Clinical features of panniculitis
The hallmark of panniculitis is the appearance of tender, erythematous to violaceous subcutaneous nodules or plaques, typically 1–5 cm in diameter. These are most commonly located on the shins (pretibial), but can involve thighs, buttocks, arms, trunk, face, or rarely deeper sites like mesentery or lungs. Lesions evolve over days to weeks: starting tender and warm, peaking with bruising, then resolving with or without atrophy (lipodystrophy). Overlying skin may show erythema, pigmentation, ulceration, or discharge in necrotising forms.
Systemic features often accompany lesions:
- Fever and chills
- Malaise and fatigue
- Arthralgia or arthritis (migratory polyarthritis)
- Myalgia
- Abdominal pain or nausea (in Weber-Christian disease)
- Weight loss in chronic cases
Severe variants may ulcerate with oily discharge or lead to panniculitis-associated morbidity like orbital involvement or systemic inflammation.
Types of panniculitis
Panniculitis is classified histopathologically into septal (inflammation at septa between fat lobules) and lobular (lobule-centric), primarily or mostly lymphocytic, neutrophilic, or granulomatous. This guides aetiology:
| Type | Key Features | Common Causes |
|---|---|---|
| Septal panniculitis | Early inflammation at fibrous septa; less fat necrosis | Erythema nodosum, scleroderma, lupus |
| Lobular panniculitis | Primarily lobular; fat necrosis common | Infections, alpha-1 antitrypsin deficiency, factitial |
| Septal & lobular | Mixed pattern | Post-steroid, pancreatic |
Major clinical types include:
- Erythema nodosum: Tender nodules on shins; self-limiting.
- Erythema induratum (Bazin’s disease): Ulcerating nodules on calves; TB-associated.
- Cytophagic histiocytic panniculitis: Histiocytes phagocytosing fat; lymphoma link.
- Alpha-1 antitrypsin deficiency panniculitis: Ulcerative with oily discharge.
- Cold panniculitis: In infants from cold exposure (popsicle panniculitis).
- Pancreatic panniculitis: Necrotising; pancreatitis link.
- Lupus panniculitis (lupus profundus): Atrophic; autoimmune.
- Infective panniculitis: Bacterial, fungal, mycobacterial.
- Factitial panniculitis: Self-induced injections.
- Idiopathic nodular panniculitis (Weber-Christian): Recurrent fever, malaise.
Causes of panniculitis
Aetiologies are multifactorial:
Infections (20–30% septal, common lobular)
- Streptococcal (most common for EN)
- Tuberculosis (erythema induratum)
- Yersinia, Campylobacter, Mycoplasma
- Fungal (e.g., histoplasmosis), atypical mycobacteria
Drugs/reactions
- Oral contraceptives, sulfonamides, minocycline
- Withdrawal of corticosteroids
Systemic disease
- Sarcoidosis (lobar granulomatous)
- IBD (EN common)
- Behçet’s syndrome
Autoimmune/connective tissue
- SLE, rheumatoid arthritis, dermatomyositis
Malignancy-associated
- Lymphoma (subcutaneous panniculitis-like T-cell lymphoma)
- Leukaemia, solid tumours
Other
- Trauma, alpha-1 antitrypsin deficiency, pancreatitis
- Idiopathic (most EN cases)
In 30–50% of erythema nodosum, no cause is identified.
Diagnosis of panniculitis
Diagnosis combines history, exam, and deep punch biopsy (4–6 mm, including fat). Biopsy differentiates types:
- Erythema nodosum: Septal panniculitis without vasculitis; Miescher radial granulomas.
- Lobular neutrophilic: Early infection/alpha-1; ‘ghost cells’ in pancreatic.
- Granulomatous: TB, sarcoid; caseation in TB.
Investigations based on suspicion:
- Throat swab, ASOT (streptococcus)
- Chest X-ray (TB, sarcoid)
- Alpha-1 antitrypsin levels
- ANA, RF for autoimmune
- Cultures from lesions
- Amylase/lipase for pancreatic
Histopathology is definitive.
Treatment of panniculitis
Treatment targets the cause; supportive for idiopathic:
- Conservative: Rest, NSAIDs (indomethacin 50–100 mg TDS), compression stockings for EN (resolves 3–6 weeks).
- Specific:
- Infection: Antibiotics/antituberculars.
- Alpha-1: Augmentation therapy, dapsone.
- Autoimmune: Steroids (prednisone 0.5–1 mg/kg), hydroxychloroquine, methotrexate.
- Pancreatic: Treat pancreatitis.
- Refractory: Thalidomide, ciclosporin, IVIG, rituximab.
Severe cases may require hospitalisation for pain/fever.
What is the differential diagnosis for panniculitis?
- Nodular vasculitis
- Erythema contusiformis (bruising)
- Polyarteritis nodosa
- Lipodermatosclerosis
- Calciphylaxis (ESRD)
- Granuloma annulare (subcutaneous)
- Insect bites
- Lymphoma cutis
Biopsy distinguishes.
Frequently asked questions about panniculitis
What causes the tender lumps in panniculitis?
Inflammation of subcutaneous fat from infections, drugs, or autoimmune triggers leads to nodule formation.
Does panniculitis go away on its own?
Many cases, like erythema nodosum, resolve spontaneously in 3–6 weeks with supportive care.
Is a biopsy always needed for panniculitis?
Yes, to classify type and identify cause via histopathology.
Can panniculitis be associated with serious diseases?
Yes, links to TB, lymphoma, IBD, and alpha-1 antitrypsin deficiency require investigation.
What is the best treatment for erythema nodosum?
NSAIDs, leg elevation, and treat underlying cause if identified.
References
- Panniculitis: Symptoms, types, and treatment — Medical News Today. 2023-10-12. https://www.medicalnewstoday.com/articles/320672
- Idiopathic Nodular Panniculitis — NORD (rarediseases.org). 2024-01-15. https://rarediseases.org/rare-diseases/panniculitis-idiopathic-nodular/
- Panniculitis – Erythema Nodosum — Perri Dermatology. 2023-05-20. https://perridermatology.com/dr-perris-blog/panniculitis-erythema-nodosum/
- Panniculitis — Merck Manuals (Professional). 2025-02-10. https://www.merckmanuals.com/professional/dermatologic-disorders/hypersensitivity-and-reactive-skin-disorders/panniculitis
- Dermatopathology Evaluation of Panniculitis — StatPearls, NCBI Bookshelf (NIH). 2024-07-05. https://www.ncbi.nlm.nih.gov/books/NBK606121/
- Panniculitis — DermNet NZ. 2025-11-18. https://dermnetnz.org/topics/panniculitis
- Getting Under Your Skin: Alpha-1 Related Panniculitis — AlphaNet. 2023-08-14. https://www.alphanet.org/community/from-our-medical-team/getting-under-your-skin-alpha-1-related-panniculitis/
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