Differential Diagnosis for Hydralazine Rash

• Single most likely diagnosis
  • Lupus-like syndrome: This is a well-documented side effect of hydralazine, especially in patients taking high doses or with a history of systemic lupus erythematosus (SLE). The rash, along with other symptoms like arthralgias and fever, can mimic SLE.
• Other Likely diagnoses
  • Drug-induced vasculitis: Hydralazine can cause a vasculitic reaction, leading to a rash that may appear as purpura, petechiae, or livedo reticularis.
  • Serum sickness-like reaction: Some patients may develop a serum sickness-like reaction to hydralazine, characterized by a rash, fever, and arthralgias.
  • Allergic contact dermatitis: Although less common, an allergic reaction to hydralazine can cause a localized or generalized rash.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Stevens-Johnson syndrome (SJS) or Toxic Epidermal Necrolysis (TEN): These are severe, life-threatening skin reactions that can be triggered by medications, including hydralazine. Early recognition and withdrawal of the offending drug are crucial.
  • Erythema multiforme: A skin condition characterized by target lesions, which can be a sign of a severe drug reaction.
• Rare diagnoses
  • Dermatomyositis: A rare autoimmune condition that can be drug-induced, including by hydralazine, characterized by skin rash and muscle weakness.
  • Lichenoid drug eruption: A rare skin reaction that can be caused by hydralazine, characterized by lichenoid papules and plaques.
  • Pemphigus: A rare autoimmune blistering disease that can be triggered by certain medications, including hydralazine.