Predisposing factors include abnormal amount of subcutaneous fat, thick ankles and abnormally poor arterial supply. Abnormal arterial supply causes low-grade ischemia of ankle region. The ankle skin becomes sensitive to temperature changes. When weather is cold, ankle is cold, blue and often tender. In hot weather, ankle becomes hot, edematous, swollen and painful. Chilblains may be present. On palpation, small superficial and painful nodules are felt. They break down to form small and multiple ulcers. Fresh crops of nodules appear in periphery of ulcer and ultimately break down. In nodular stage, pain is present; while it subsides in ulcerative stage.
Erythema induratum
Nodular lichen myxedematosus
Nevus depigmentosus
Aromaticum rosatum
Lichen myxedematosus
Nevus lipomatosus superficialis
Ichthyosis bullosa of Siemens
Keratosis follicularis