Panniculitis is a collective term for conditions involving inflammation of the fat layer under the skin (panniculus adiposus), which lies between the skin and muscles and helps keep the body warm. The inflammation causes tender nodules that often look like small bruises, typically on the shins, but they can also appear on the arms or other areas with fatty tissue.

Symptoms vary, but common features include sore, tender nodules with red, purple, or darker discoloration. The pain can be bothersome enough to affect daily life and may cause psychological discomfort due to visible changes. Other symptoms can include fever, fatigue, joint and muscle pain, and in some cases nausea or vomiting. The condition can lead to complications such as sores, cracks, thinning or thickening of the skin, and in severe cases, open wounds with a risk of infection.

Panniculitis is rare but can affect all age groups – from infants to adults. Some types occur more frequently in specific age groups, for example in young children after exposure to cold (cold panniculitis). The causes vary: infections (such as bacteria, fungi, HIV, tuberculosis), cold, trauma, medications, autoimmune diseases like lupus or Crohn’s disease, and underlying disorders such as inflammatory bowel disease or pancreatic disease. Some types are associated with inflammation of blood vessels or tissue necrosis.