In children with highly suspected SM, further diagnostic steps include histological and immunohistochemical examination of BM with staining for tryptase, CD117, CD25, CD2, and CD30, evaluation of BM smear using Wright-Giemsa or May-Grünwald-Giemsa stain, flow cytometry (same markers as above) and determination of KIT D816V mutation in BM according to the same standards as previously described in detail for adults [1,2,3,4,85]. Here, KIT is linked to systemic mastocytosis.