Persistent solitary lesion in an 8-month-old boy


The mother of a healthy 8-month-old boy pops into your office for an urgent visit seeking advice on a golden brown bump on her son’s lower back, visible since 2 months of age. This morning when he awoke, it appeared angry, red, and swollen although the swelling seems to be improving. What’s your diagnosis?

The Case

The mother of a healthy 8-month-old boy pops into your office for an urgent visit seeking advice on a golden brown bump on her son’s lower back, visible since 2 months of age. This morning when he awoke, it appeared angry, red, and swollen although the swelling seems to be improving. What’s your diagnosis?


Solitary mastocytoma



Solitary mastocytomas are the second most common form of childhood-onset cutaneous mastocytosis, accounting for approximately 10% to 15% of cases.1They often develop before 1 year of age, with most presenting within the first 3 months of life. Adult involvement is rare, but has been reported in recent literature.2

Molecular pathogenesis

Mastocytomas, classified as myeloproliferative neoplasms, are believed to be caused by increased local concentrations of soluble mast cell growth factor, which stimulates local mast cell and melanocyte proliferation and increases local production of melanin pigment responsible for the hyperpigmented appearance of the cutaneous lesion.3 Several genetic mutations have been implicated in the pathogenesis, including impaired mast cell apoptosis as evidenced by up-regulation of the apoptosis-preventing protein BCL-2 and activating mutations of the proto-oncogene c-kit.4,5 Additionally, elevations in interleukin-6 levels have been observed and correlated with disease severity in cutaneous mastocytosis.6

Diagnosis and treatment

Mastocytomas range in size from 1 cm to 4 cm and may present as single or several (referred to as urticarial pigmentosa) erythematous and golden-to-brown subtly elevated plaques, often with a leathery or peau d’orange texture. When a lesion is stroked, the release of histamine results in urticaria formation with the development of local erythema and edema. This change is referred to as the Darier sign, which is explainable on the basis of mast cell degranulation induced by physical stimulation.

Blistering may occur particularly in young infants when mastocytomas develop in areas subject to recurrent trauma, such as in the diaper area or around skin creases. Clinical examination is usually sufficient to make a diagnosis. However, a skin biopsy for histologic confirmation may be necessary in equivocal cases.

Most mastocytomas are not symptomatic. However, lesions causing intense pruritus may be treated with potent topical corticosteroids. Intralesional corticosteroids also may be helpful in reducing lesion size and associated symptoms. Surgical excision is usually reserved for intractable cases.

Although significant systemic disease is rare, mastocytomas may be associated with flares of asthma or extracutaneous symptoms, including pruritus, flushing, headaches, and gastrointestinal complaints. Symptoms usually respond to oral antihistamines and, when necessary, oral cromolyn sodium and/or phototherapy.

Differential diagnosis

The characteristic skin lesions and Darier sign differentiate solitary mastocytomas from a broad differential diagnosis that includes pigmented nevi, xanthoma, juvenile xanthogranuloma, neurofibroma, hemangioma, granuloma annulare, Spitz nevus, pseudolymphomas, and arthropod bites.


Mastocytomas are benign and generally involute spontaneously either completely or partially by adulthood. However, prognosis is related to age at presentation, with children manifesting skin lesions within the first 2 years of life most likely to undergo spontaneous resolution.7 Parents can be reassured that persistent symptoms or progression to systemic mastocytosis is rare.



1. Briley LD, Phillips CM. Cutaneous mastocytosis: a review focusing on the pediatric population. Clin Pediatr (Phila). 2008;47(8):757-761.

2. Pandhi D, Singal A, Aggarwal S. Adult onset, hypopigmented solitary mastocytoma: report of two cases. Indian J Dermatol, Venereol Leprol. 2008;74(1):41-43.

3. Akay BN, Kittler H, Sanli H, Harmankaya K, Anadolu R. Dermatoscopic findings of cutaneous mastocytosis. Dermatology. 2009;218(3):226-230.

4. Hartmann K, Artuc M, Baldus SE, et al. Expression of Bcl-2 and Bcl-xL in cutaneous and bone marrow lesions of mastocytosis. Am J Pathol. 2003;163(3):819-826.

5. Noack F, Escribano L, Sotlar K, et al. Evolution of urticaria pigmentosa into indolent systemic mastocytosis: abnormal immunophenotype of mast cells without evidence of c-kit mutation ASP-816-VAL. Leuk Lymphoma. 2003;44(2):313-319.

6. Brockow K, Akin C, Huber M, Metcalfe DD. IL-6 levels predict disease variant and extent of organ involvement in patients with mastocytosis. Clin Immunol. 2005;115(2):216-223.

7. Uzzaman A, Maric I, Noel P, Kettelhut BV, Metcalfe DD, Carter MC..Pediatric-onset mastocytosis: a long term clinical follow-up and correlation with bone marrow histopathology. Pediatr Blood Cancer. 2009;53(4), 629-634. 

MR SEMENOV is a 4th-year medical student at Johns Hopkins University School of Medicine, Baltimore, Maryland. DR COHEN, section editor for Dermatology: What’s Your Dx?, is director, Pediatric Dermatology and Cutaneous Laser Center, and associate professor of pediatrics and dermatology, Johns Hopkins University School of Medicine, Baltimore. The author and section editor have nothing to disclose regarding affiliations with or financial interests in any organization that may have an interest in any part of this article. Vignettes are based on real cases that have been modified to allow the author and editor to focus on key teaching points. Images also may be edited or substituted for teaching purposes.

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