One of the more confusing aspects of mastocytosis is that childhood mastocytosis often bears little resemblance to adult-onset mastocytosis and has a very different natural history. Cutaneous mastocytosis in children is the most common presentation of mastocytosis. True systemic mastocytosis (meeting WHO SM criteria) is quite rare in pediatric cases.
A recent paper describes the features of 105 children assessed at the NIH. They found that the children in this group either had a stable disease state or improved, with 30-65% getting better over time. None of the children received cytoreductive therapy.
They found that in this group, children with normal baseline tryptase levels had negative bone marrow biopsies. A single elevated tryptase level was not determined to correlate well with to a positive bone marrow, rather an elevated baseline tryptase was a good indicator of SM. No children without systemic mastocytosis had organ swelling.
Likewise, all children with systemic mastocytosis had both elevated baseline tryptase and swelling of internal organs. Bone marrow mast cell burden correlated well with tryptase value. The average tryptase for children with SM in this study was 111.5 ng/ml. Tryptase decreased over time in some SM children. The researchers recommended evaluation of serum tryptase every 6-12 months.
All children with organ swelling were found to have SM. Children with swelling of both liver and spleen were found to be positive for the D816V CKIT mutation. Swelling of both of these organs indicates that disease is more likely to persist into adulthood. Of total 19 children with SM, 16 were positive for the CKIT D816V mutation.
In children with UP, the average tryptase value was 5.9 ng/ml. Twelve children with UP had tryptase values of 11-20, and six had values over 20. Children with UP most often saw significant decreases in tryptase levels over time. Most UP children with skin and minor GI issues had normal tryptase values.
Children with DCM had much higher average tryptase values, with an average of 67. 85% of DCM children had tryptase over 20 ng/ml when diagnosed. None of them had swelling of organs.
Of 105 children assessed in this study, 3 had elevated monocytes; 22 had elevated white blood cells; and 12 had elevated platelets. All of these values returned to normal by the end of the study. Seven had increased clotting time (PTT). Of those with longer clotting times, four had lupus antibodies and one had Factor VII deficiency. All seven PTT values returned to normal. Two children with DCM and one with UP had iron deficiency anemia. One patient had significant elevation of alkaline phosphatase, which resolved. Researchers noted an inverse correlation between serum tryptase and IgE levels in this group.
Reference:
Carter et al. Assessment of clinical findings, tryptase levels, and bone marrow histopathology in the management of pediatric mastocytosis. J Allergy Clin Immunol 2015.