Children with rare diseases of neutrophil granulocytes: from therapeutic orphans to pioneers of individualized medicine.

Neutrophil granulocytes are the most abundant immune cells in the blood yet the pathways orchestrating their differentiation and biological function remain incompletely understood. Studying (ultra-) rare patients with monogenetic defects of neutrophil granulocytes may open new horizons to understand basic principles of hematopoiesis and innate immunity. Here, recent insights into genetic factors controlling myelopoiesis and their more general role in biology will be presented in a clinical perspective. Advances in supportive care, first and foremost the use of recombinant human granulocyte-colony stimulating factor, has made a substantial difference for the quality of life and life expectancy of patients with congenital neutropenia (CN). Up to date, the only definitive cure can be provided by transplantation of allogeneic hematopoietic stem cells. The elucidation of the underlying molecular factors contributing to defective differentiation and function of neutrophil granulocytes nurtures new ideas of targeted individualized therapies.