Differential Diagnosis for Diffuse Lacy Blanching Pink Rash in a 10-Year-Old Girl

• Single Most Likely Diagnosis
  • Erythema infectiosum (Fifth disease): This is the most likely diagnosis due to the characteristic "slapped cheek" appearance and lacy, reticular rash that often follows. It's a common illness in children, caused by parvovirus B19.
• Other Likely Diagnoses
  • Viral exanthem: Various viral infections can cause similar rashes, and the presentation can be non-specific. Viruses such as enteroviruses, adenoviruses, and others could be responsible.
  • Allergic reactions: Allergic contact dermatitis or drug reactions could potentially cause a similar rash, although the lacy pattern might be less common.
  • Kawasaki disease: Although more commonly associated with fever, lymphadenopathy, and desquamation, the rash in Kawasaki disease can sometimes appear as a lacy, erythematous rash.
• Do Not Miss Diagnoses
  • Meningococcemia: This is a life-threatening condition caused by Neisseria meningitidis. While the rash is typically petechial or purpuric, early stages might appear as a non-specific erythematous rash. It's crucial to consider this diagnosis due to its high mortality rate if untreated.
  • Rocky Mountain spotted fever: Caused by Rickettsia rickettsii, this tick-borne illness can present with a rash that might initially appear as a lacy, erythematous pattern before evolving into the characteristic petechial rash.
  • Juvenile idiopathic arthritis (JIA): Systemic JIA can present with a rash, fever, and other systemic symptoms. The rash can be variable but might appear as a lacy, evanescent rash.
• Rare Diagnoses
  • Lupus erythematosus: Systemic lupus erythematosus (SLE) can present with a variety of skin manifestations, including a malar rash that might appear lacy. However, SLE is rare in children and would typically be accompanied by other systemic symptoms.
  • Dermatomyositis: This autoimmune condition can cause a characteristic heliotrope rash and Gottron's papules, but it might also present with a more non-specific, lacy rash in some cases.