Differential Diagnosis for Swelling and Itching of Right Hand and Foot in a 4-Year-Old Male

Single Most Likely Diagnosis

• Allergic Contact Dermatitis: This is a common condition in children, caused by an allergic reaction to substances like nickel, latex, or certain plants. The symptoms of swelling and itching, especially if localized to one hand and foot, could be indicative of an allergic reaction to something the child has come into contact with.

Other Likely Diagnoses

• Insect Bites or Stings: Children often experience bites or stings from insects like mosquitoes, bees, or ants, which can cause localized swelling and itching.
• Eczema (Atopic Dermatitis): A chronic condition characterized by dry, itchy skin, and is common in children. It can cause swelling and itching, particularly if the child has scratched the area.
• Impetigo: A contagious skin infection that can cause red sores, swelling, and itching, often on the face but can spread to other areas including hands and feet.
• Scabies: A skin infestation caused by the itch mite, leading to intense itching and swelling, especially in areas like between fingers and toes.

Do Not Miss Diagnoses

• Cellulitis: A bacterial skin infection that can cause swelling, redness, and pain. It's less common in children but can be serious if not treated promptly.
• Deep Vein Thrombosis (DVT): Although rare in children, DVT can cause swelling and pain in the affected limb. It's crucial to consider, especially if there's a history of recent immobilization or trauma.
• Kawasaki Disease: An acute illness that mainly affects children, characterized by fever, rash, swelling of hands and feet, and other symptoms. It's essential to diagnose early to prevent complications.

Rare Diagnoses

• Erythema Multiforme: A skin condition characterized by target lesions, which can be accompanied by swelling and itching. It's often triggered by infections or medications.
• Juvenile Idiopathic Arthritis: An autoimmune disease that can cause joint swelling and pain, potentially accompanied by skin symptoms.
• Lymphangitis: An infection of the lymphatic vessels, which can cause red streaks, swelling, and pain, usually following a skin infection.

Each of these diagnoses should be considered based on the child's full clinical presentation, including any additional symptoms, recent activities, and medical history. A thorough examination and possibly further testing may be necessary to determine the exact cause of the swelling and itching.