Panniculitis Following Subcutaneous Injections

 

Factors affecting the type and severity of the panniculitis:

(1) volume of material

(2) number of injections

(3) sites of injection (thickness of fat layer, presence of fascia or underlying bone)

(4) duration of injections

(5) sterility of material and injection technique, with risk of cellulitis

(6) chemical irritability of material injected

(7) host response, including allergic reaction

 

Mechanism:

(1) accidental medical (intramuscular, intradermal or intravascular injection that reaches the subcutaneous fat)

(2) drug abuse

(3) psychiatric (factitious)

(4) criminal behavior, involving fraud or a prisoner (may be factitious)

(5) occupational

 

Materials injected:

(1) pharmaceuticals or illicit drugs

(2) plant material

(3) chemicals

(4) feces

 

Clinical history:

(1) history of injections (see also Chapter 32), especially by an inexperienced health care provider

(2) observation or past history of behavior

(3) some form of secondary gain, including legal action

(4) inconsistencies in story

(5) accessibility of needles and syringes

 

Physical findings

(1) distribution

(1a) exposed skin in occupational exposures, especially hands and forearms

(1b) absence in sites not reachable by patient

(2) stages of evolution (inflamed vs resolving vs scarred)

(3) urticaria

(4) tender, erythematous nodules

(5) ulcerations

 

Histologic features:

(1) material injected, especially if polarizable (may include plant material, meat fibers, crystals)

(2) granulomas with foreign body type giant cells

(3) necrosis and fat necrosis

(4) neutrophilic and/or eosinophilic infiltrate

(5) calcium deposits

(6) fibrosis

 

Differential diagnosis:

(1) traumatic panniculitis

(2) infectious cellulitis (may be secondary to self-injections)

(3) lipogranuloma and paraffinoma

(4) other forms of panniculitis