Foreign modelling agent reactions

Last revised by Angel Donato on 22 Aug 2023

Foreign modelling agent reactions (FMAR), also known as iatrogenic allogenosis, the latter term is primarily found in the Spanish literature and has created some controversy. It is a reaction from solid or liquid substances injected for aesthetic reasons, especially in the calves, face, buttocks, and breasts. Foreign modelling agents or  "biopolymers" that may be used include liquid silicone, mineral oil, paraffin, liquid petroleum, animal fat, acrylic, and many more.

The adverse reactions to soft tissue filling substances are local and general: 

  • local
    • erythema, swelling, pain, pigmentation, fibrosis, infection, necrosis, ulceration etc.  
  • general
    • fever, chills, malaise
    • pulmonary embolism of silicone
    • systemic granulomatous sequelae
      • hepatitis
      • acute/chronic renal failure
      • erosive arthropathy
      • systemic sclerosis-like disease
    • death

Specimen analysis indicates chronic granulomatous inflammation with a foreign body reaction, with foamy histiocytes or multinucleated giant cells with phagocytized foreign material. Fibrotic areas may appear interspersed with the granulomatous response.

Grayscale ultrasound image show hyperechoic deposits in the dermis and subcutaneous tissue with a "snowstorm" pattern.

CT may be used to determine the dimensions and densities of substances in soft tissues and is an essential component of preoperative planning for surgery.

Signal characteristics vary according to the substance used:

  • T1: rounded hypo to isointense material
  • T2: rounded hyperintense material
  • T1 C+: heterogeneous enhancement by an inflammatory process

Treatments include:

  • incision and drainage of abscesses
  • surgical removal/debridement of necrotic tissue
  • surgical/ultrasound liposuction
  • medication: anti-inflammatory drugs, systemic steroids.

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Cases and figures

  • Case 1
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