Background: Histiocytosis encompass highly heterogeneous proliferative disorders of the
mononuclear phagocyte system. Recently they have been reclassified by the Histiocyte
Society (2016) and reviewed in WHO classifications of hematopoietic (2017) and skin
tumours (2018). These entities range from single-system and often self-limiting to
multisystem and life-threatening forms. Recently the frequent association of NonLangerhans Cell Histiocytosis with myeloid neoplasms has been highlighted.
Observation: We hereby describe three cases of histiocytosis who subsequently developed
acute myeloid leukemia. All of them were male, with a mean age of 53 years old. Patient
(pt.) 1 was diagnosed with Indeterminate cell histiocytosis, pt. 2 with diffuse
Reticulohistiocytosis and pt. 3 with a mixed histiocytosis. Pt.1 and pt.2 present with
generalized papulo-nodular skin eruption. Instead, pt.3 initially presents oral mucous
membrane lesions and one year later displayed bone and skin involvement. Leukemic
evolution occurred in pt.1 and pt.3 following chemotherapy while pt.2 developed acute
myeloid leukemia after two years of observational follow up. In pt.1 and pt.2, both the
conventional and molecular cytogenetics approaches detect clinically significant
chromosome abnormalities. Both pt.1 and pt.3 died few months after the diagnosis of
leukemia, whereas pt.2 is currently alive, in complete remission and good general conditions
after chemotherapy and allogenic stem cell transplantation.
Key message: Cutaneous histiocytosis are bone-marrow derived disorders which may be
considered to some extent as skin manifestation of dysmielopoiesis (i.e. result of an altered
genetic background). Therefore, in some cases, histiocytosis patients are at increased risk
of developing myeloid neoplasms such as myeloid leukemia and
myeloproliferative/myelodysplastic neoplasms. For such patients (especially adults with
generalized skin eruption) is highly recommended a tight follow up and constant
surveillance regarding clinical manifestation of leukemia (e.g. recurrent infection, anemia,
pancytopænia)
