Infective Panniculitis: 4 Key Types, Diagnosis & Treatment
Comprehensive guide to infective panniculitis: causes, symptoms, diagnosis, and treatment options for subcutaneous fat infections.
Infective panniculitis is a rare form of panniculitis characterised by inflammation of the subcutaneous fat due to microbial infection. It primarily affects individuals with immunodeficiency, such as those with HIV or on immunosuppressive therapy, though it can occur in immunocompetent people via direct inoculation or haematogenous spread.
What is panniculitis?
Panniculitis refers to inflammation of the subcutaneous adipose tissue, the fat layer beneath the skin. It manifests as tender, erythematous nodules or plaques, often on the lower extremities, but can appear anywhere on the body. While non-infective causes like trauma, drugs, or autoimmune diseases are common, infective panniculitis arises from bacterial, mycobacterial, fungal, or viral pathogens invading the subcutaneous layer.
The condition is distinguished by its lobular or septal inflammatory pattern on histopathology. Infective cases typically show a lobular panniculitis with suppuration, granulomas, or necrosis, depending on the organism. Early recognition is crucial, as untreated infections can lead to dissemination, especially in immunocompromised hosts.
Who gets infective panniculitis?
Infective panniculitis predominantly occurs in patients with weakened immune systems. Key risk factors include:
- Human immunodeficiency virus (HIV) infection
- Immunosuppressive drugs post-organ transplantation
- Chemotherapy or corticosteroid use
- Chronic diseases like diabetes or malignancy
- Direct trauma allowing microbial entry in immunocompetent individuals
In immunocompetent patients, it often results from local inoculation, such as injections or surgery, leading to single lesions. In contrast, disseminated forms in the immunocompromised present with multiple widespread nodules. Children and adults are affected, with mycobacterial cases more common in specific demographics exposed to atypical strains.
What causes infective panniculitis?
Infective panniculitis stems from direct inoculation of pathogens into subcutaneous tissue or haematogenous seeding from systemic infections. Pathogens include bacteria, mycobacteria, fungi, and rarely viruses or parasites.
Bacterial panniculitis
Common bacteria include Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, and anaerobes like Bacteroides. These cause suppurative lobular panniculitis, often post-trauma or in IV drug users. In systemic sepsis, subcutaneous seeding leads to multifocal lesions.
Mycobacterial panniculitis
Mycobacteria, especially atypical ones like Mycobacterium chelonae, M. haemophilum, M. avium complex, cause granulomatous panniculitis. Rapidly growing mycobacteria infect via trauma in healthy individuals or disseminate in AIDS patients. Tuberculosis (M. tuberculosis) rarely presents as panniculitis.
Fungal panniculitis
Fungi such as Cryptococcus neoformans, Histoplasma capsulatum, Coccidioides, or Sporothrix schenckii cause either disseminated disease in immunocompromised patients or subcutaneous mycoses from inoculation. Lesions range from nodules to ulcers.
Viral panniculitis
Rarely, viruses like herpes zoster, cytomegalovirus (CMV), or herpes simplex virus (HSV) trigger panniculitis, often in transplant recipients. Histology shows viral inclusions amid inflammation.
Clinical features
Infective panniculitis lacks pathognomonic signs; features depend on the organism and host immunity:
- Painful, tender, erythematous subcutaneous nodules or plaques, 1–10 cm
- Locations: legs (most common), arms, trunk, face
- Evolution: warm, indurated, may ulcerate, suppurate, or form abscesses
- Systemic: fever, chills, weight loss in disseminated cases
- Immunocompromised: multiple lesions, rapid progression
Unlike erythema nodosum (septal, tender shins), infective forms are often lobular with suppuration.
Diagnosis
Diagnosis combines clinical suspicion, imaging, and confirmatory biopsy. History of immunosuppression, travel, or trauma guides investigation.
- Imaging: Ultrasound shows hypoechoic nodules; MRI delineates depth and abscesses.
- Biopsy: Essential. Punch or incisional biopsy reveals lobular panniculitis, neutrophils, granulomas, or organisms. Special stains (Gram, Ziehl-Neelsen, GMS, PAS) and cultures (aerobic, anaerobic, mycobacterial, fungal) are mandatory.
- Microbiology: PCR or serology for atypical pathogens.
Differential includes non-infective panniculitis (e.g., erythema nodosum, lupus panniculitis), subcutaneous sarcoma, or metastatic disease.
Bacterial panniculitis
Histology: lobular/septal suppurative panniculitis with neutrophils, abscesses, fat necrosis. Gram stain identifies bacteria; cultures confirm.
Treatment: Drainage of abscesses plus targeted antibiotics. Empiric: amoxicillin-clavulanic acid or vancomycin. Duration: 2–6 weeks.
Mycobacterial panniculitis
Histology: granulomatous lobular panniculitis; acid-fast bacilli on Ziehl-Neelsen stain.
Treatment varies by species:
| Mycobacterium | Treatment | Surgery |
|---|---|---|
| M. chelonae, M. abscessus | Clarithromycin + amikacin/cefoxitin | Debridement/excision |
| M. marinum | Ethambutol + rifampicin or doxycycline | Debridement |
| M. ulcerans | Ethambutol + clarithromycin + rifampicin | Surgical excision |
Multi-drug therapy for 6–18 months; monitor resistance.
Fungal panniculitis
Histology: granulomatous or suppurative; GMS/PAS stains yeast/hyphae.
| Type | Clinical | Histology | Management |
|---|---|---|---|
| Disseminated | Multiple nodules | Lobular panniculitis | Itraconazole/amphotericin B (months) |
| Subcutaneous mycosis | Single nodule | Lobular panniculitis | Surgical excision |
Antifungals tailored to species; high mortality in disseminated disease.
Viral panniculitis
Histology: lobular inflammation with viral inclusions. PCR confirms. Treatment: antivirals (e.g., aciclovir for HSV, ganciclovir for CMV) plus immunosuppression reduction.
Management
Treatment targets the pathogen while supporting the host:
- Surgical: Incision/drainage, debridement, excision for localised disease.
- Medical: Antibiotics/antifungals/antimycobacterials based on culture.
- Supportive: Analgesics (NSAIDs), elevation, compression. Corticosteroids cautiously if non-infective inflammation suspected.
- Prognosis: Good with early ID in immunocompetent; poor in disseminated immunocompromised cases.
Frequently Asked Questions
What is the most common cause of infective panniculitis?
Bacterial infections like Staphylococcus aureus or streptococci are frequent, especially post-trauma.
Can infective panniculitis occur in healthy people?
Yes, via direct inoculation (e.g., injections, injuries), typically presenting as solitary lesions.
How is the diagnosis confirmed?
Deep biopsy with cultures and special stains; imaging aids but is not definitive.
What are the treatment options for mycobacterial panniculitis?
Combination antibiotics (e.g., clarithromycin, rifampicin) for months, often with surgery.
Is fungal panniculitis curable?
Yes, with prolonged antifungals like itraconazole; surgery for localised mycoses.
References
- Infection and panniculitis — PubMed. 2010-07-28. https://pubmed.ncbi.nlm.nih.gov/20666820/
- Infective panniculitis — DermNet NZ. Recent access. https://dermnetnz.org/topics/infective-panniculitis
- Panniculitis – Reviewing the basics — Dermatology Times. Recent access. https://www.dermatologytimes.com/view/panniculitis–reviewing-basics
- Idiopathic Nodular Panniculitis — NORD (National Organization for Rare Disorders). Recent access. https://rarediseases.org/rare-diseases/panniculitis-idiopathic-nodular/
- Panniculitis: Symptoms, types, and treatment — Medical News Today. Recent access. https://www.medicalnewstoday.com/articles/320672
Similar Articles
Read full bio of Sneha Tete
