Panniculitis

Panniculitis is a group of diseases whose hallmark is inflammation of subcutaneous fatty and muscle tissue. Symptoms include tender skin nodules, and systemic signs such as weight loss and fatigue.

Histological
It can occur in any fatty tissue (cutaneous or visceral) and is often diagnosed on the basis of a deep skin biopsy, and can be further classified by histological characteristics based on the location of the inflammatory cells (within fatty lobules or in the septa which separate them) and on the presence or absence of vasculitis.

There are thus four main histological subtypes:
 * 1) lobular panniculitis without vasculitis (acute panniculitis, previously termed Weber-Christian disease, systemic nodular panniculitis)
 * 2) lobular panniculitis with vasculitis
 * 3) septal panniculitis without vasculitis
 * 4) septal panniculitis with vasculitis

Symptomatic
Panniculitis can also be classified based on the presence or absence of systemic symptoms:
 * Panniculitis without systemic disease can be a result of trauma or cold ;
 * Panniculitis with systemic disease can be caused...
 * by connective tissue disorders such as lupus erythematosus or scleroderma;
 * by lymphoproliferative disease such as lymphoma or histiocytosis;
 * by pancreatitis or pancreatic cancer;
 * and by many other causes.

Associated conditions
Lipoatrophy (the loss of subcutaneous tissue) can occur in any of these conditions.