Mastocytosis in children

Mast cell disease in children is strictly cutaneous in 90% of cases, with the remaining 10% having systemic disease.  In cutaneous disease, urticaria pigmentosa is found about 80% of the time; mastocytoma, 11%; diffuse cutaneous mastocytosis, 9%.  Prognosis for children with these diseases is generally good.  Pediatric mast cell disease usually improves markedly or resolves completely before puberty. 

In 85% of patients, skin lesions formed before the age of 2.  Diffuse cutaneous mastocytosis is found exclusively in children less than a year old.  In 13% of cases, another family member also had mastocytosis. 

Disease was benign in 80% of children.  All children with systemic mastocytosis presented initially with this disease and did not progress from another diagnosis.  There is no known disease course in which children progress from indolent SM to more aggressive disease.  15-30% cases of childhood SM continue into adulthood, with the rest resolving fully.

As in adults, symptoms vary greatly.  Systemic symptoms are often seen in children with cutaneous disease, although not with solitary mastocytomas.  The most common symptoms are itching, flushing, blisters and GI symptoms.  Children with severe, blistering rashes are at highest risk for anaphylaxis.    

Children are diagnosed in much the same way as adults, with biopsy of lesions and testing for markers, including receptors seen on neoplastic mast cells, the D816V CKIT mutation and serum tryptase levels.  Treatment is also similar, with antihistamines, leukotriene antogonists, mast cell stabilizers and topical steroids.  Chemotherapy is not indicated in cutaneous disease or indolent SM.

In cutaneous disease, mutations were found in codon 816 (the location of the CKIT gene) 42% of the time, with mutations outside of this outside found 44% of the time.  Furthermore, many of these mutations affected the CKIT receptor differently than in adults.  This finding reinforces the idea that childhood mastocytosis is different from adult mastocytosis.