Paediatric mastocytosis
- NIAID/NIH, Bethesda, MD, USA
- Correspondence to:
Dr M C Carter, NIH/NIAID/LAD, Building 10, Room 11-C206, 10 Center Dr. MSC 1881, Bethesda, MD 20892-1881, USA;
mcarter{at}niaid.nih.gov
An unusual disease in infants and children
Mastocytosis in infants and children is an unusual disease characterised by an excess of mast cells in body tissues. The phenotypic expression of the disease is dependent on the pattern of localisation of the mast cells to specific organs and the release of mast cell mediators. The skin is the most common organ involved in children and may be the only manifestation of the disease. Mastocytosis can present from birth1 to adulthood, with adult onset disease generally being more severe. The cutaneous form was recognised over 100 years ago, but the term mastocytosis, based on the offending cell, was initiated in 1936 by Sezary and Chauvillon.2
AETIOLOGY AND PATHOGENESIS
Mast cells are most abundant in connective tissues, with a predilection for peripheral nerves, and blood and lymphatic vessels. It is at these sites, under the influence of cytokines (interleukins 3, 4, 5, 6, 9, 10, and 15)3–9 and the principal mast cell growth factor, stem cell factor (SCF), that mast cells differentiate from a CD34+ pluripotent haematopoietic stem cell.10 This pluripotential cell expresses the receptor for SCF, KIT (CD117), but does not yet express the high affinity IgE receptor, FcεRI.11 SCF is present in a soluble and membrane bound form and is produced by fibroblasts, endothelial cells, and bone marrow stromal cells. This growth factor orchestrates the complete cycle of the mast cell from proliferation to differentiation.12 Mastocytosis in some instances appears to be the clinical expression of disregulation of the production and function of mast cells caused by distinct activating somatic mutations in c-KIT (table 1).13 KIT is a type III transmembrane tyrosine kinase with an extracellular domain that binds mast cell growth factor, also known as SCF. Additionally, KIT is expressed by and is essential for …
