Stasis Dermatitis: This condition is a common cause of erythema on the lower extremities, particularly around the ankles. It occurs due to poor circulation, leading to fluid buildup and inflammation. The likelihood of stasis dermatitis is high due to its prevalence in individuals with venous insufficiency.

Cellulitis: A bacterial infection of the skin and subcutaneous tissues, often presenting with erythema, warmth, and swelling. It's a common condition that can affect any part of the body, including the lower extremities.
Eczema (Atopic Dermatitis): Can cause erythema and is often seen in individuals with a history of atopy. It may involve the ankles, especially if there's an allergic component or irritation from footwear.
Contact Dermatitis: An allergic or irritant reaction to substances coming into contact with the skin, such as certain metals in jewelry, dyes in socks, or chemicals in footwear materials.

Deep Vein Thrombosis (DVT): Although DVT typically presents with swelling and pain, erythema can be a part of the clinical picture. Missing this diagnosis can be fatal due to the risk of pulmonary embolism.
Necrotizing Fasciitis: A severe infection that can start with erythema but rapidly progresses to necrosis of the fascia and skin. Early recognition is crucial for survival.
Erythema Nodosum: An inflammatory condition characterized by tender erythematous nodules, often on the shins. While not usually fatal, it can be a sign of underlying systemic disease.

Erythromelalgia: A disorder characterized by burning pain, heat, and redness in the hands and feet. It can be primary or secondary to other conditions like myeloproliferative disorders.
Livedoid Vasculopathy: A rare condition involving inflammation of the blood vessels, leading to painful, ulcerative lesions on the lower extremities, often around the ankles.
Kawasaki Disease: Although more common in children, it can cause erythema of the extremities among other symptoms. It's a rare but important diagnosis due to its potential for cardiac complications.