Introduction. Erythrocytosis is a common reason for a hematology consultation. Most of the patients are over 50 years of age. The diagnostic approach is already well established, but determining the etiology of erythrocytosis in the young adult may be a real diagnostic challenge. Hereditary causes are often first suspected, but the real etiologic panorama of erythrocytosis in this population is still poorly understood.

Methods. This Canadian single-center retrospective observational study was conducted in a Québec university hospital over a period of 20 years (1995 - 2015). Data were collected by a single investigator in a standardized database. From a computer-generated query over a chosen period of time, all patients between 16 and 35 years of age with high levels of hemoglobin or hematocrit were selected (hemoglobin > 185 g/L and/or hematocrit > 0.52 in men; hemoglobin > 165 g/L and/or hematocrit > 0.48 in women). Files were analyzed after approval from the scientific and ethical committees.

Results. 426 patients fulfilled the above criteria (on a total of 113 453 complete blood counts conducted in the same age range during the analysis period), but only 56 benefitted from further investigations. Only those cases were included in the study. The male-to-female ratio was 5 : 3. Among them, 59% were smokers, 11% had a high alcohol intake and 27% were using drugs on a regular basis. Obesity was present in 43% of patients (morbid obesity in nearly one third of cases). More than half of the patients had one visit or less with a specialist for investigation of their erythrocytosis. Among those who had a medical follow-up, the median length is 42 months. Erythropoietin was measured in 23% of cases and the JAK2 mutation was screened in 18% of cases. The diagnosis of an acquired polycythemia was made in 41% of cases: hypoxemia (n= 13), renal disorders (n = 6) and drug-induced (n= 4). No case of myeloproliferative syndrome was identified. Two cases were associated with congenital polycythemia (high oxygen affinity hemoglobinopathy). Diagnosis of relative polycythemia was made in slightly over 10% of cases (n= 7). In 24 patients, no conclusive cause could be identified. One third of those patients (n= 8) were hospitalised for mental health decompensation or self-induced intoxication when high hemoglobin levels were detected. When JAK2 mutation testing was not available, the complete blood count was further analyzed and it did not provide any evidence for myeloproliferative syndrome. One in five patients received treatment for their polycythemia, whatever the cause: aspirin (n= 7) and phlebotomy (n= 5). There has been no reported patient death associated with polycythemia or its treatment. Only two major complications occurred: thrombosis (n =1) and bleeding (n= 1).

Conclusion. This is the first study to specifically analyze erythrocytosis in young adults. Despite the retrospective design, it demonstrates patient management often inconsistent with the actual recommendations and a lack of follow-up after initial investigations. Congenital polycythemia deserves to be systematically evoked in this age range, but represents only a small part of cases. Acquired polycythemia dominates the etiologies whereas myeloproliferative syndromes were not depicted in this study. Harmonisation of patient care for young adults with erythrocytosis is therefore highly desirable.


No relevant conflicts of interest to declare.

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