Rash in Infants and Young Children

History of present illness focuses on the time course of illness, particularly the relationship between the rash and other symptoms.

Review of systems focuses on symptoms of causative disorders, including gastrointestinal symptoms (suggesting immunoglobulin A–associated vasculitis [formerly called Henoch-Schönlein purpura] or hemolytic-uremic syndrome), joint symptoms (suggesting immunoglobulin A–associated vasculitis or Lyme disease), headache or neurologic symptoms (suggesting meningitis or Lyme disease).

Past medical history should note any drugs recently used, particularly antibiotics and anticonvulsants. Family history of atopy is noted.

Examination begins with a review of vital signs, particularly to check for fever. Initial observation assesses the infant or child for signs of lethargy, irritability, or distress. A full physical examination is done, with particular attention to the characteristics of the skin lesions, including the presence of blistering, vesicles, petechiae, purpura, or urticaria and mucosal involvement. Children are evaluated for meningeal signs (neck stiffness, Kernig and Brudzinski signs), although these signs are often absent in children < 2 years.

The following findings are of particular concern:

• Blistering or skin sloughing

• Diarrhea and/or abdominal pain

• Fever and inconsolability or extreme irritability

• Mucosal inflammation

• Petechiae and/or purpura

• Urticaria with respiratory distress

Well-appearing children without systemic symptoms or signs are unlikely to have a dangerous disorder. The appearance of the rash typically narrows the differential diagnosis. The associated symptoms and signs help identify patients with a serious disorder and often suggest the diagnosis ( see Table: Some Causes of Rash in Infants and Children).

Bullae and/or sloughing suggest staphylococcal scalded skin syndrome or Stevens-Johnson syndrome and are considered dermatologic emergencies. Conjunctival inflammation may occur in Kawasaki disease, measles, staphylococcal scalded skin syndrome, and Stevens-Johnson syndrome. Any child presenting with fever and petechiae or purpura must be evaluated carefully for the possibility of meningococcemia. Bloody diarrhea with pallor and petechiae should raise concern about the possibility of hemolytic uremic syndrome. Fever for > 5 days with evidence of mucosal inflammation and rash should prompt consideration of and further evaluation for Kawasaki disease.

For most children, the history and physical examination are sufficient for diagnosis. Testing is targeted at potential life threats; it includes Gram stain and cultures of blood and cerebrospinal fluid for meningococcemia; complete blood count, renal function tests, and stool tests for hemolytic uremic syndrome).