Differential Diagnosis for the Described Rash

• Single most likely diagnosis
  • Erythema multiforme: This condition is characterized by target lesions, which are often seen on the palms and soles. The description of sharply demarcated lesions with dark red centers on the dorsal and plantar aspects of the feet, along with involvement of the palmar aspect of the hands, aligns closely with erythema multiforme, particularly its major form which can be triggered by infections or medications.
• Other Likely diagnoses
  • Secondary syphilis: This condition can cause a variety of skin manifestations, including rashes on the palms and soles. However, the rash in secondary syphilis is typically more diffuse and may not always present with the targeted appearance described.
  • Fixed drug eruption: This condition can cause well-demarcated lesions that can appear on the hands and feet, but they are usually solitary or few in number and recur at the same site with re-exposure to the offending drug.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Stevens-Johnson syndrome (SJS) and Toxic Epidermal Necrolysis (TEN): These are severe skin conditions usually triggered by medications. They can present with target lesions and involvement of the mucous membranes, and are medical emergencies due to their high morbidity and mortality.
  • Rocky Mountain spotted fever: This tick-borne illness can cause a rash on the palms and soles, but it is typically accompanied by fever, headache, and other systemic symptoms. The rash may start as small, flat, pink, non-itchy spots but can develop into a more severe form.
• Rare diagnoses
  • Kawasaki disease: Although more common in children, Kawasaki disease can cause a rash, fever, and other systemic symptoms. The rash can vary in appearance but may include target-like lesions.
  • Pemphigus or other autoimmune bullous diseases: These conditions can cause blistering skin lesions that might, in some cases, resemble target lesions, though they are less likely to present with the specific pattern described.