Panniculitis (plural: panniculitides 1) is a non-specific histopathological term referring to inflammation of adipose tissue. It most commonly affects subcutaneous fat, although internal forms, e.g., mesenteric panniculitis, are well-known 1,2.
Clinical presentation
Most panniculitides present similarly with multiple reddened nodules, characteristically on the lower extremities. Therefore determining specific causation requires histological study 2.
Pathology
Panniculitis is traditionally subdivided into two main forms based upon whether it predominantly involves the septa or lobules of the adipose tissue.
- septal panniculitis
- lobular panniculitis
Although in practice, most forms demonstrate the involvement of both lobules and septa 2. The further subdivision is predicated on whether vasculitis is present; most are non-vasculitic.
A few cutaneous lymphomas mimic panniculitis clinically and histopathologically. However, they are not truly inflammatory, rather malignant diseases in nature.
Etiology
Septal panniculitis
- non-vasculitic
- erythema nodosum
- iatrogenic: post treatment with biologic agents
- lipodermatosclerosis
- radiation
- morphea profunda
- necrobiosis lipoidica profunda
- vasculitic
Lobular panniculitis
- non-vasculitic
- pancreas-related panniculitis
- alpha-1-antitrypsin deficiency
- SLE-related
- dermatomyositis-related
- Sweet syndrome: subcutis type
- eosinophilic panniculitis
- factitial panniculitis
- cold panniculitis
- iatrogenic: steroid injections
- ischemic (lipomembranous)
- sclerema neonatorum
- neonatal subcutaneous fat necrosis
- vasculitic
- erythema induratum
- Rosai-Dorfman disease
- infectious panniculitis