Decision to perform bone marrow biopsy in an adult with suspected systemic mastocytosis (SM) presenting WITH skin lesions

MPCM/UP: maculopapular cutaneous mastocytosis/urticaria pigmentosa; CBC: complete blood count.
* MPCM can be diagnosed based on the characteristic appearance +/- presence of Darier's sign, but if clinician is unsure or Darier's sign is not present and clinical suspicion is high, perform 3 mm punch biopsy to confirm. Skin biopsy findings are described in the topic on evaluation and diagnosis of mastocytosis in adults.
¶ Concerning abnormalities on the CBC with differential include eosinophilia, monocytosis, immature neutrophils, circulating mast cells, or other abnormalities that may require further evaluation of the bone marrow. These are discussed in detail in the topic on determining the subtype of systemic mastocytosis. The results of peripheral blood KIT analysis provides information about the presence of clonal disease and may impact the need for bone marrow biopsy. Refer to discussion of KIT mutational analysis in topic on evaluation and diagnosis of mastocytosis in adults.