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A 6-month-old male with solitary mastocytoma


An otherwise healthy 6-month-old boy has a 1-cm area of recurrent blistering with surrounding erythema on his right cheek that developed shortly after birth.

The case

An otherwise healthy 6-month-old boy has a 1-cm area of recurrent blistering with surrounding erythema on his right cheek that developed shortly after birth.

Diagnosis: Solitary mastocytoma with blistering

Solitary bullous eruption with surrounding erythema

Solitary bullous eruption with surrounding erythema

Clinical findings

Mastocytosis is a condition that involves an accumulation of mast cells in 1 or more organ systems such as the skin, liver, bone marrow, or small intestine.1 Cutaneous mastocytosis (CM) is usually found in very young children and predominantly involves dermal infiltrates of mast cells.2 The condition can be divided into maculopapular CM, diffuse CM, and solitary CM. The prognosis of solitary CM is excellent, with most patients experiencing spontaneous resolution before puberty. However, in patients with disease onset after age 2 years, solitary CM may continue into adulthood.3 Children with solitary lesions, multiple skin lesions, or diffuse mastocytosis confined to the skin (rare in infants) all have a good prognosis. Diffuse cutaneous disease with systemic involvement is much less common in infants and is often persistent. It is rarely associated with myeloproliferative disease.4


The incidence of CM is estimated to be around 5 to 10 new cases in 1 million individuals, or 1 in every 1000 to 8000 dermatology outpatients, but it may be as often as 1 in 200 first-time patients at pediatric dermatology clinics.5 It is estimated that 10% to 15% of all pediatric cases of CM are solitary CM. Although the condition typically affects infants, particularly in the first 3 months of life, there have been reported cases of adult onset.3

Most cases of mastocytosis are due to a gain-of-function mutation in the c-KIT gene, which encodes a receptor tyrosine kinase that regulates cell growth and division in addition to regulating the production of mast cells. Most of these somatic mutations occur spontaneously and are therefore not heritable.3 However, there have been some case reports of familial cases.6

Differential diagnosis

When the patient’s skin lesion is stroked or rubbed, mast cell degranulation occurs and forms a wheal known as Darier sign. Blisters result from buildup of tryptase between the epidermis and dermis.3 Although not usually necessary, diagnosis can be confirmed by a skin biopsy, which would show a dense infiltrate of mast cells.6 Additionally, during an attack, tryptase and histamine levels may be increased. An absence of systemic systems should be noted to rule out systemic mastocytosis, which could show more extensive blistering in a larger surface area, a high serum total tryptase level, gastrointestinal disturbances, osteolysis, organomegaly, ascites, or cytopenias.6

Treatment and management

Patients should avoid triggers of mast cell degranulation. Common triggers include heat, friction, alcohol, narcotics, sunlight, nonsteroidal anti-inflammatory drugs, anesthetics, bee stings, and more. When symptoms are triggered, they can be managed with antihistamines, sodium cromoglycate, acetylsalicylic acid, or ketotifen. Topical steroids may be used to manage lesion progression, and topical antibiotics can be used to prevent infection in blisters.2

Patient outcome

When the area with recurrent blistering was rubbed, the infant developed a blister with surrounding urticarial erythema, typical of a positive Darier sign. The patient was given an oral antihistamine for symptomatic treatment, and a discussion was had with his parents about ways to avoid rubbing the area. Over the next 3 to 4 months, the blistering stopped and the redness with rubbing improved dramatically. The patient’s parents were counseled that continued regression of the lesion and improvement in symptoms should be expected.


  1. Cleveland Clinic. Mastocytosis. Updated November 18, 2015. Accessed July 28, 2020. https://my.clevelandclinic.org/health/articles/5908-mastocytosis#:~:text=Mastocytosis%20is%20a%20condition%20that,of%20the%20body%20are%20affected
  2. Koga H, Kokubo T, Akaishi M, Iida K, Korematsu S. Neonatal onset diffuse cutaneous mastocytosis: a case report and review of the literature. Pediatr Dermatol. 2011;28(5):542-546. doi:10.1111/j.1525-1470.2010.01212.x
  3. Leung AKC, Lam JM, Leong KF. Childhood solitary cutaneous mastocytoma: clinical manifestations, diagnosis, evaluation, and management. Curr Pediatr Rev. 2019;15(1):42-46. doi:10.2174/1573396315666181120163952
  4. Azaña JM, Torrelo A, Matito A. Update on mastocytosis (part 2): categories, prognosis, and treatment. Actas Dermosifiliogr. 2016;107:15-22. doi: 10.1016/j.adengl.2015.11.002
  5. Horny H-P, Sotlar K, Valent P, Hartmann K. Mastocytosis: a disease of the hematopoietic stem cell. Dtsch Arztebl Int. 2008;105(40):686-692. doi:10.3238/arztebl.2008.0686
  6. Azaña JM, Torrelo A, Matito A. Update on mastocytosis (part 1): pathophysiology, clinical features, and diagnosis. Actas Dermosifiliogr. 2016;107(1):5-14. doi:10.1016/j.ad.2015.09.007
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