Panniculitis is a group of diseases whose hallmark is inflammation

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

 of subcutaneous adipose tissue (the fatty layer under the skin - panniculus adiposus

Panniculus adiposus

The panniculus adiposus is the fatty layer of the subcutaneous tissues, superficial to a deeper vestigial layer of muscle, the panniculus carnosus.It includes structures that are considered fascia by some sources but not by others....

). Symptoms include tender skin nodules, and systemic signs such as weight loss

Weight loss

Weight loss, in the context of medicine, health or physical fitness, is a reduction of the total body mass, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon and other connective tissue...

 and fatigue

Fatigue (physical)

Fatigue is a state of awareness describing a range of afflictions, usually associated with physical and/or mental weakness, though varying from a general state of lethargy to a specific work-induced burning sensation within one's muscles...

.

Restated, an inflammatory disorder primarily localized in the subcutaneous fat is termed a "panniculitis," a group of disorders that may be challenging both for the clinician and the dermatopathologist.

Histological

It can occur in any fatty tissue (cutaneous or visceral) and is often diagnosed on the basis of a deep skin biopsy

Biopsy

A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...

, 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

Vasculitis

Vasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type 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
  Physical trauma
  Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
  
   or cold;
• Panniculitis with systemic disease can be caused...
  • by connective tissue
    Connective tissue
    "Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...
    
     disorders such as lupus erythematosus
    Lupus erythematosus
    Lupus erythematosus is a category for a collection of diseases with similar underlying problems with immunity . Symptoms of these diseases can affect many different body systems, including joints, skin, kidneys, blood cells, heart, and lungs...
    
     or scleroderma
    Scleroderma
    Systemic sclerosis or systemic scleroderma is a systemic autoimmune disease or systemic connective tissue disease that is a subtype of scleroderma.-Skin symptoms:...
    
    ;
  • by lymphoproliferative disease such as lymphoma
    Lymphoma
    Lymphoma is a cancer in the lymphatic cells of the immune system. Typically, lymphomas present as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and can be curable depending on the histology, type, and stage...
    
     or histiocytosis
    Histiocytosis
    In medicine, histiocytosis refers to an excessive number of histiocytes, , and is typically used to refer to a group of rare diseases which share this as a characteristic...
    
    ;
  • by pancreatitis
    Pancreatitis
    Pancreatitis is inflammation of the pancreas. It occurs when pancreatic enzymes that digest food are activated in the pancreas instead of the small intestine. It may be acute – beginning suddenly and lasting a few days, or chronic – occurring over many years...
    
     or pancreatic cancer
    Pancreatic cancer
    Pancreatic cancer refers to a malignant neoplasm of the pancreas. The most common type of pancreatic cancer, accounting for 95% of these tumors is adenocarcinoma, which arises within the exocrine component of the pancreas. A minority arises from the islet cells and is classified as a...
    
    ;
  • by sarcoidosis with cutaneous involvement (seen in up to 20 percent)
  • and by many other causes.

Associated conditions

Lipoatrophy

Lipoatrophy

Lipoatrophy is the term describing the localized loss of fat tissue. This may occur as a result of subcutanous injections of insulin in the treatment of diabetes, from the use of human growth hormone or from subcutanous injections of Copaxone used for the treatment of multiple sclerosis. In the...

 or lipodystrophy

Lipodystrophy

Lipodystrophy is a medical condition characterized by abnormal or degenerative conditions of the body's adipose tissue. A more specific term, lipoatrophy is used when describing the loss of fat from one area...

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

See also

• Erythema induratum
• Erythema nodosum
  Erythema nodosum
  Erythema nodosum is an inflammation of the fat cells under the skin characterized by tender red nodules or lumps that are usually seen on both shins...
  
  
• Panniculus adiposus
  Panniculus adiposus
  The panniculus adiposus is the fatty layer of the subcutaneous tissues, superficial to a deeper vestigial layer of muscle, the panniculus carnosus.It includes structures that are considered fascia by some sources but not by others....
  
  
• Panniculus carnosus
  Panniculus carnosus
  The panniculus carnosus is a part of the subcutaneous tissues in the study of animal anatomy. It is a layer of striated muscle deep to the panniculus adiposus. In humans the platysma muscle of the neck, palmaris brevis in the hand, and the dartos muscle in the scrotum are described as a discrete...
  
  
• Lipodermatosclerosis
  Lipodermatosclerosis
  Lipodermatosclerosis is a skin and connective tissue disease. It is a form of lower extremity panniculitis, an inflammation of the layer of fat under the epidermis.- Symptoms :Pain may be the first noticed symptom...
  
  
• List of cutaneous conditions