PKLR and histiocytic sarcoma: Finally, since, independently from the coexistence of the heterozygous PK mutation, all the family members with HS have been followed for 6 years since the diagnosis and have exhibited similar clinical phenotype and OGE pattern, it can be assumed that the PKLR deficient variant does not modulate the clinical expression of HS, and that ektacytometry is as a valuable clinical tool for the diagnosis of HS.