Involvement of Fat

Involvement of Fat                     See DX Path for details of the conditions below


Look at this topic from an aetiological point of view rather than that of a septal or lobular histology.
Clinically Panniculitis presents as painful red or purple nodules particularly on the shins in erythema nodosum,

However there is also the indurated thick white skin on the medial ankle in lipodermatosclerosis, sometimes seen in chronic stasis.

Panniculitis can also ulcerate particularly pancreatic panniculitis and erythema induratum or nodular vasculitis where the ulcers are often on the calf.

Many deep fungal or mycobacterial infections will involve the fat layer. Send tissue for culture when biopsying.

 Lupus panniculitis is a rare variant of lupus erythematosus which gives painful indurated red swellings not just on the legs but also the arms and buttocks.

 Subcutaneous T cell lymphoma is rare but both T cell and B cell lymphomas can present on the legs. These are discussed in more detail below.

 When you initially look at a slide you see a normal epidermis with a relatively clear dermis and all the inflammation is in the subcutaneous fat. You look to see if there is any vasculitis and whether the inflammation is septal or lobular or both. You then check the inflammatory cell type and any associated fibrosis.

Septal Panniculitis  Erythema nodosum  Subacute nodular migratory panniculitis Morphea/scleroderma panniculitis  Alpha-1 antitrypsin deficiency panniculitis

Panniculitis with lots of lymphocytes or plasma cells Morphea/scleroderma panniculitis Lupus erythematosus panniculitis Panniculitis of dermatomyositis Subcutaneous panniculitis-like T-cell lymphoma Cutaneous γ/δ T-cell lymphoma

  View the video below on Panniculitis