Differential Diagnosis

The patient's symptoms of small patches of pink skin that itch, are not spreading, but will not go away, along with a significant other having similar symptoms and the presence of cats and dogs in the home, suggest several potential diagnoses. These can be categorized as follows:

• Single Most Likely Diagnosis
  • Eczema (Atopic Dermatitis): This is a common condition characterized by itchy, inflamed skin. The fact that the patches are not spreading and the presence of pets (which could contribute to allergies) supports this diagnosis. Eczema can be chronic and is often seen in individuals with a family history of allergies or asthma.
• Other Likely Diagnoses
  • Contact Dermatitis: This condition is caused by an allergic reaction or irritation to substances that come into contact with the skin, such as pet dander, soaps, or certain metals. Given the patient's exposure to cats and dogs, this is a plausible diagnosis.
  • Seborrheic Dermatitis: Characterized by a red, itchy rash, typically on the scalp, but can also appear on oily areas of the body. It's common and could be exacerbated by stress or environmental factors, including the presence of pets.
  • Flea Bites: Given the presence of cats and dogs, flea bites could cause itchy, pink patches, especially if the fleas are jumping from the pets to the humans.
• Do Not Miss Diagnoses
  • Scabies: A highly contagious skin infestation by the mite Sarcoptes scabiei. The fact that the significant other also has symptoms raises the possibility of scabies, which would require immediate treatment to prevent further spread.
  • Ringworm (Tinea Corporis): A fungal infection that can cause circular, itchy patches. It's contagious and can be spread by contact with infected animals, making it a critical diagnosis not to miss, especially with pets in the home.
• Rare Diagnoses
  • Pityriasis Rosea: An uncommon skin condition that causes a rash, often starting with a single, large spot (herald patch) followed by smaller spots. It's usually self-limiting but could be considered if other diagnoses are ruled out.
  • Cutaneous T-Cell Lymphoma (Mycosis Fungoides): A rare type of skin cancer that can cause patches of skin to become red, scaly, and itchy. It's much less likely but should be considered if the condition does not respond to typical treatments for the above diagnoses.

Each of these diagnoses has different implications for treatment and management, emphasizing the importance of a thorough diagnostic workup.