Differential Diagnosis for New Onset Erythematous Rash and Fatigue

Given the symptoms of a new onset erythematous rash on both cheeks and the bridge of the nose, along with fatigue, and a history of Hashimoto thyroiditis being treated with Synthroid, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Lupus: The "butterfly" rash on the cheeks and nose is a classic symptom of Systemic Lupus Erythematosus (SLE), especially in someone with a history of autoimmune disease like Hashimoto thyroiditis. The fatigue also aligns with lupus, which can cause widespread inflammation and affect multiple body systems.

• Other Likely Diagnoses

  • Rosacea: This condition can cause a similar erythematous rash on the face, including the cheeks and nose, and can be exacerbated by various factors including sun exposure, stress, and certain medications.
  • Seborrheic Dermatitis: A common skin condition that can cause a red, itchy rash on the face, including areas like the nose and cheeks. It's more common in individuals with autoimmune diseases.
  • Photosensitivity Reaction: Given the location of the rash, a photosensitivity reaction, possibly due to medication or an underlying condition, could be considered, especially if the patient has increased sun exposure.

• Do Not Miss Diagnoses

  • Sarcoidosis: Although less common, sarcoidosis can present with skin manifestations, including a rash on the face, and can also cause fatigue. It's an autoimmune disease that can affect multiple organs, making early diagnosis crucial.
  • Dermatomyositis: An inflammatory disease characterized by skin rash and muscle weakness. The rash can appear on the face, including the cheeks and nose, and is often accompanied by other symptoms like fatigue.

• Rare Diagnoses

  • Erythema Multiforme: A skin condition characterized by target lesions, which can appear on the face among other areas. It's often triggered by infections or medications.
  • Granuloma Faciale: A rare skin condition that causes a persistent, erythematous plaque, typically on the face. It's more common in middle-aged men but can occur in anyone.
  • Sjögren's Syndrome: An autoimmune disorder that can cause skin rashes, among other symptoms like dry eyes and mouth. It often coexists with other autoimmune diseases like lupus or rheumatoid arthritis.

Each of these conditions has a different set of diagnostic criteria and potential treatments, emphasizing the importance of a thorough medical evaluation to determine the underlying cause of the symptoms.