Pruritic Urticarial Papules and Plaques of Pregnancy (PUPPP): This condition is the most common dermatosis in pregnancy, characterized by itchy, bumpy rashes that often start in the abdominal striae and can spread to other areas, including the ankles. Its onset typically occurs in the third trimester.

Atopic Dermatitis (Eczema): Pregnancy can exacerbate atopic dermatitis, leading to itchy, bumpy rashes on various parts of the body, including the ankles.
Contact Dermatitis: An allergic reaction or irritant contact dermatitis could cause itchy, bumpy rashes on the ankles, especially if new products or substances have come into contact with the skin.
Insect Bites: Mosquito or other insect bites can cause itchy, bumpy reactions on the skin, which might be more pronounced during pregnancy due to increased sensitivity.

Pemphigoid Gestationis: A rare autoimmune skin disorder that occurs during pregnancy, characterized by itchy blisters. Although rare, it's critical to diagnose due to potential risks to the fetus and the need for specific treatment.
Deep Vein Thrombosis (DVT): While DVT typically presents with swelling, warmth, and pain rather than an itchy rash, in some cases, it can cause skin changes. Given the risk of pulmonary embolism, it's essential to consider DVT, especially in pregnant women who are at higher risk.

Impetigo Herpetiformis: A rare dermatosis of pregnancy that resembles pustular psoriasis, characterized by itchy, bumpy pustules. It's associated with significant maternal and fetal risks if not properly managed.
Prurigo of Pregnancy: A condition characterized by extremely itchy nodules that can appear anywhere on the body, including the ankles. It's less common than PUPPP but can be very distressing for the patient.