Rolf Kostmann (1909-1982) was a Swedish pediatrician and army doctor. He was the first to describe an inherited form of chronic neutropenia in childhood. In 1956, Kostmann published his article "Infantile genetic agranulocytosis" in Acta Paediatrica. "Infantile agranulocytosis," as Rolf Kostmann named this hereditary syndrome, has been known for more than half a century, yet the underlying genetic mutations have remained unknown for many decades. Fifty years later, homozygous mutations in the gene encoding the mitochondrial protein HCLS1-associated X1 were found in affected members of the original Kostmann pedigree. Therefore, the eponym "Kostmann disease" best fits this specific mutation and mode of inheritance. The identification of genetic cause now allows the analysis of genotype-phenotype correlations. After the development of recombinant human granulocyte colony-stimulating factor (G-CSF), the prognosis and quality of life improved dramatically. Hematopoietic stem cell transplantation remains the only currently available treatment for refractory cases to G-CSF and patients who have transformed into leukemia.