Differential Diagnosis for Itchy Rash on Chest and Lower Legs

• Single most likely diagnosis
  • Atopic Dermatitis (Eczema): This condition is characterized by itchy, inflamed skin that can lead to open wounds due to scratching. The distribution on the chest and lower legs is common, especially in adults.
• Other Likely diagnoses
  • Contact Dermatitis: An allergic or irritant reaction to substances coming into contact with the skin, leading to itchy rashes and potential open wounds from scratching.
  • Dry Skin (Xerosis): Especially common on the legs, dry skin can be very itchy and lead to scratching that results in open wounds.
  • Insect Bites: Repeated bites from insects like mosquitoes or bed bugs can cause itchy rashes and lead to scratching until the skin is broken.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Cutaneous T-Cell Lymphoma (Mycosis Fungoides): A rare type of skin cancer that can present with itchy skin lesions. Although rare, missing this diagnosis could have severe consequences.
  • Bullous Pemphigoid: An autoimmune disease that causes blistering of the skin, which can be itchy and lead to open sores. It's more common in older adults and can be serious if not treated.
• Rare diagnoses
  • Scabies: A parasitic infection caused by the scabies mite, leading to intense itching and rash, typically in areas like the fingers, wrists, and groin, but can spread to other areas.
  • Lichen Simplex Chronicus: A condition characterized by thickened skin due to chronic scratching, leading to itchy, leathery patches on the skin.
  • Dermatitis Herpetiformis: An autoimmune skin condition associated with celiac disease, characterized by intensely itchy blisters on the skin, typically on the elbows, knees, and buttocks.