4/25: PEM Case of the Week

-Dr. Yvonne Guinta, MD

A 2-year-old girl presents to the ED with complaint of fever and she is refusing to walk. Her father states that she has been sick for approximately 1 week. She was evaluated by her pediatrician 8 days ago and was started on Augmentin for otitis media. Two days ago, she had pain in her feet and ankles.

One day ago, a rash developed, which is unchanged today.

Vitals 39.1°C, HR is 102/min, RR is 20/min, and BP is 110/72

MSK: Her ankles and wrists are swollen and tender

Skin: She has a widespread rash over her entire body with 3- to 5-cm erythematous wheals that blanch.

What is the most likely diagnosis?

Differential includes:

Erythema multiforme

Henoch Schonlein Purpura

Serum Sickness-like reaction

Urticaria Multiforme

Serum Sickness-like reaction

This child has a serum sickness-like reaction.  This is an immune complex-mediated reaction.  In this case, the Augmentin is a likely trigger.  It can be difficult to differentiate between serum sickness, erythema multiforme and urticaria multiforme.  All three include a rash.  

• The rash of serum sickness and erythema multiforme is fixed.  The lesions of urticaria multiforme wax and wane.

• Serum sickness may be erythemaous and purpuric.

• Arthritis and arthralgias are more prominent in serum sickness than erythema multiforme or urticaria multiforme.  However, hand and foot edema is common in urticaria multiforme.

• Fever is a key feature in serum sickness but not in erythema multiforme or urticaria multiforme.

• HSP presents with a prominent purpuric rash and arthralgias.  (Remember that the arthralgias can present before any evidence of a rash so keep this in mind with any non-traumatic ankle pain).  No fever.

Thanks for reading,

Yvonne

For More info on Serum Sickness