A 4-year-old boy presents to your clinic for evaluation of the following lesions. They have been present since birth and are sometimes pruritic.

Which of the following statements is/are true regarding this condition?

A. NSAIDs, opioids, iodinated contrast, and venomous stings may exacerbate

B. Most likely associated with systemic features such as fever, night sweats, diarrhea, flushing, bronchospasm

C. Blistering can be elicited with rubbing or scratching

D. Important for surgical teams to be aware of the diagnosis

E. Serum tryptase levels are not helpful in diagnosis or monitoring 

Rationale: Correct diagnosis identification is critical to answering this question. Pictured above are several reddish-brown papules and patches on a young child which is most consistent with maculopapular cutaneous mastocytosis also known as urticaria pigmentosa. It is the most common form of mastocytosis observed in children. C-kit mutations have been associated with this condition. The abundant mass cells can be triggered by various factors and release their contents (such as histamine, cytokines, heparin, proteases) leading to symptoms such as pruritus. Most patients have only cutaneous findings/symptoms and tend to have an excellent prognosis. Treatment is geared at avoiding triggers and managing symptoms such as pruritus with anti-histamines; it is also important to provide patients with epinephrine pen autoinjection due to risk of anaphylaxis. 

Correct answers: A, C, D

A. NSAIDs, opioids, iodinated contrast, and venomous stings may exacerbate

Various medications and stings (including jellyfish) can trigger mast cell stimulation. It is important for patients and families to be aware of these potential triggers and to avoid these medications. Heat and stress are other common triggers.

C. Blistering can be elicited with rubbing or scratching

The Darier sign is elected in urticaria pigmentosa by rubbing or scratching one of the lesions, resulting in urticarial or even bullous reactions. It is important to avoid eliciting this in numerous lesions to avoid a systemic response such as anaphylaxis.

D. Important for surgical teams to be aware of the diagnosis

Certain anesthetics and medications as noted above can trigger mast cell activation. Surgical teams, particularly anesthesiologists, should be aware of the diagnosis for surgical planning. 

Incorrect answers:

B. Most likely associated with systemic features such as fever, night sweats, diarrhea, flushing, bronchospasm

Most children with urticaria pigmentosa do not have systemic symptoms. The presence of systemic symptoms warrants further workup by a hematologist/oncologist as systemic involvement of the mastocytosis is possible. This may include CBC, CMP, imaging studies, serum tryptase, or bone marrow biopsy. 

E. Serum tryptase levels are not helpful in diagnosis or monitoring

Checking tryptase levels can help screen for systemic involvement as levels > 20ng/mL can be suggestive of systemic involvement. Having a baseline tryptase level can also be helpful for comparison if the disease course changes as there is a value to compare against when checking a new tryptase level. 

Additional reading at Weinberg's Color Atlas of Pediatric Dermatology Section 20: Disorders of the Dermis (Infiltrates, Atrophies, and Nodules)