Differential Diagnosis for Palmar Maculopapular Rash and Fever

The patient's presentation of a palmar maculopapular rash and fever, with fever spikes every 2-3 days and palmar erythema coinciding with fever, suggests a systemic condition with a periodic fever pattern. Here's a categorized differential diagnosis:

• Single most likely diagnosis
  • Still's Disease (Adult-Onset Juvenile Rheumatoid Arthritis): Characterized by high fevers, salmon-colored rash, and joint pain. The rash often appears during fever spikes and can be maculopapular, making it a strong candidate given the patient's symptoms.
• Other Likely diagnoses
  • Infective Endocarditis: Although more commonly associated with systemic symptoms like heart murmurs, embolic phenomena, and Janeway lesions, some cases can present with fever and rash, including on the palms.
  • Systemic Lupus Erythematosus (SLE): SLE can cause a wide range of skin manifestations, including a maculopapular rash, and is often accompanied by systemic symptoms like fever. However, the periodic nature of the fever and the specific localization to the palms might be less typical.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Meningococcemia: This condition can present with fever, rash (which can be maculopapular and evolve into petechiae or purpura), and can have a rapid progression. The rash can sometimes appear on the palms. Given its high mortality rate if untreated, it's crucial not to miss this diagnosis.
  • Rocky Mountain Spotted Fever (RMSF): Characterized by fever, headache, and a rash that can appear on the palms and soles. The rash typically evolves from maculopapular to petechial. RMSF is a tick-borne illness that requires prompt treatment to prevent serious complications.
• Rare diagnoses
  • Sweet Syndrome (Acute Febrile Neutrophilic Dermatosis): Presents with fever, an elevated number of neutrophils, and tender, erythematous, well-demarcated papules and plaques that can appear on the palms. It's a rare condition but should be considered in the differential diagnosis of fever and rash.
  • Erythema Marginatum: Associated with acute rheumatic fever, it's a rare condition characterized by a maculopapular rash that can appear on the trunk and limbs, including the palms, and is accompanied by fever and other symptoms of rheumatic fever.

Each of these diagnoses has distinct features, but the periodic fever pattern and the specific involvement of the palms with erythema during fever spikes are key clues that guide the differential diagnosis.