Mechanical causes – local pressure or repetitive blunt trauma
Physical causes – skin exposure to cold (eg, Popsicle or ice cube), heat, or electricity (eg, site of electrode, electrostimulation, or electroacupuncture needles)
Chemical causes – syringe or needle injection of disparate materials such as:
- Organic materials including acids, alkalis, milk, or microbiologically contaminated substances such as saliva, urine, or feces
- Cosmetic materials including bovine collagen, polymethyl methacrylate microspheres, and polydimethylsiloxane, and, less commonly, paraffin (mineral oil) and vegetable oils (cottonseed, sesame, or camphor oil)
- Therapeutic agents including vitamin K, povidone, meperidine, pentazocine, gold salts, vaccines (eg, tetanus antitoxoid), glatiramer acetate (treatment for multiple sclerosis), and cytotoxic chemotherapies (eg, anthracyclines, vinca alkaloids, or taxanes)
The atypical distribution of the lesions will often suggest an exogenous origin. However, the wide range of possible causes and lack of reliable patient history make the diagnosis of FP difficult, sometimes requiring multiple admissions before the cause of the lesions is discovered.
The inflammation is self-limited with minimal systemic symptoms unless there is concurrent infection. In these cases, the patient may develop abscesses and lymphangitic spread if not treated. In cases of deliberate self-injury, the subcutaneous inflammation may appear resistant to treatment or chronically recurring. However, when the affected areas are covered with bandages or protective casts, there is pronounced and rapid improvement.
Related topics: panniculitis, cold panniculitis, factitial dermatitis, factitial ulcer
M79.3 – Panniculitis, unspecified
238884009 – Factitial panniculitis
- Alpha-1 antitrypsin deficiency-associated panniculitis – Family history of emphysema and/or liver disease, decreased α-1 antitrypsin levels, and atypical pulmonary function test results.
- Erythema induratum (nodular vasculitis) – Distinct histologic features and may be associated with Mycobacterium tuberculosis infection.
- Erythema nodosum – Classically found on the anterior shins and associated with an underlying disease (eg, sarcoidosis or inflammatory bowel disease).
- Lupus erythematosus profundus (lupus panniculitis) – Distinct histologic features, resolved lesions have areas of scarring and atrophy, and antinuclear antibody (ANA) positive in 70% of cases.
- Pancreatic panniculitis – Elevated serum amylase and lipase levels, focal calcification and "ghost adipocytes" on histology, and patient is severely ill.
- Polyarteritis nodosa – Purpura, livedo reticularis, and Raynaud phenomenon; biopsy reveals small- to medium-vessel vasculitis; classically perinuclear antineutrophil cytoplasmic antibody (p-ANCA [myeloperoxidase]) positive.
- Poststeroidal panniculitis (see panniculitis) – Following rapid withdrawal of oral corticosteroids.
- Pyoderma gangrenosum – Usually purulent and exhibits pathergy.
- Subcutaneous panniculitis-like T-cell lymphoma – B symptoms (eg, fever, night sweats, and weight loss) and atypical cells on biopsy.
- Superficial thrombophlebitis – Forms along the course of a vein in the lower leg and biopsy reveals large subcutaneous vein with central thrombosis.
- Suppurative / chronic skin infections (eg, methicillin-resistant Staphylococcus aureus [MRSA], nocardiosis, actinomycosis, atypical mycobacterial infection, and Old World or New World leishmaniasis) – Ulcerative lesions; tissue cultures and biopsy required to distinguish between skin infections.
- Systemic sclerosis – Physical examination findings and serology (anti-Scl-70, anticentromere, and anti-RNA polymerase I or II antibodies).
- Weber-Christian disease – Recurrent fever and malaise.
- Medium-vessel vasculitides, such as granulomatosis with polyangiitis, may present with erythematous nodules with or without livedo reticularis / racemosa.