A 9-month-old male infant is brought to the clinic for evaluation of a rash involving the hands, feet, and ankles. The lesions seem to be quite pruritic. A similar rash occurred several weeks ago and resolved without treatment. Photographs of the rash are shown below.

No burrows are seen on examination and potassium hydroxide prep and bacterial cultures are negative. The child is otherwise well. No family members have similar rashes. 

What is the most appropriate next step in management?

A. Oral antibiotics
B. Topical permethrin 5%
C. High potency topical corticosteroids
D. Oral antihistamines and emollients
E. Oral acyclovir

Rationale:

Multiple etiologies can present as a pustulo-vesicular eruption in young children. Our patient's presentation is most consistent with infantile acropustulosis which is characterized by repeat waves of pruritic pustules on the palms, soles, and dorsal feet. These episodes typically begin in early infancy, recur every few weeks, and often resolve by 2 to 3 years of age. The etiology of infantile acropustulosis is unclear - some propose it is a hypersensitivity reaction to prior scabies infection. However, infantile acropustulosis often persists despite appropriate scabies treatment and lacks hallmark findings such as burrows or mite identification on scraping. 

Correct answer: C. High potency topical corticosteroids

High potency topical corticosteroids are the treatment of choice for infantile acropustulosis as they provide effective symptomatic relief during flares. While the condition is self-limited, flares can be distressing and may recur for many months.

Incorrect answer choices:

A. Oral antibiotics. Although pustules are present, this is not representative of a bacterial infection as the lesions are sterile and cultures are negative. 

B. Topical permethrin 5%. Scabies is a reasonable consideration due to the acral distribution and pruritus. However, the absence of burrows or mite identification in addition to the history of spontaneous resolution favors infantile acropustulosis. 

D. Oral antihistamines and emollients may offer adjunctive symptomatic relief but are insufficient alone for controlling flares. They do not adequately suppress the underlying inflammatory process and are best used in combination with topical corticosteroids.

E. Oral acyclovir. Herpes simplex virus infection in neonates typically presents with grouped vesicles on an erythematous base and does not present as pruritic recurring crops of vesico-pustules on acral surfaces. Additionally, our patient is afebrile and thriving which makes HSV much less likely. 

Additional reading at Color Atlas & Synopsis of Pediatric Dermatology Section 1: Cutaneous findings in the newborn