Final answer:
Erythema nodosum is characterized by inflammation resulting in red nodules on the skin and is associated with various conditions such as contact dermatitis, tuberculin reactions, and autoimmune diseases.
Step-by-step explanation:
Erythema nodosum is a condition associated with inflammation in the subcutaneous fat cells of the hypodermis, which leads to the formation of red nodules or lumps on the skin, typically on the legs or face. Although sometimes resulting from a streptococcal infection, erythema nodosum can also be associated with other conditions. Such conditions include contact dermatitis, tuberculin reaction, and various autoimmune diseases such as diabetes mellitus type I, multiple sclerosis, and rheumatoid arthritis, as well as other skin disorders like eczema and acne.