Introduction
People with Down syndrome often present with abnormalities in blood cells, including red blood cells (which carry oxygen throughout the body), white blood cells (which fight infection), and platelets (which help stop bleeding). Some of these changes may be associated with other medical complications, but in many cases abnormalities are identified without an obvious underlying cause and resolve spontaneously over time. This is particularly common in newborns with Down syndrome, although some changes may persist throughout a person's life. Evaluation and treatment by a haematologist or oncologist may be necessary.
What Are the Most Common Blood Cell Abnormalities in Down Syndrome?
The most commonly diagnosed blood cell abnormalities in individuals with Down syndrome include: polycythaemia, macrocytosis, thrombocytopaenia, thrombocytosis, leucopaenia, leukaemoid reaction, and transient myeloproliferative disorder (TMD).
Polycythaemia (Elevated Red Blood Cell Count)
Polycythaemia refers to an elevated number of red blood cells and is commonly seen in newborns with Down syndrome. In some affected infants, the elevated red cell count is associated with certain forms of congenital heart defects; however, the vast majority of infants with Down syndrome who have polycythaemia do not have associated cardiac defects. The condition typically resolves within the first few months of life, particularly when no underlying medical condition is present. Generally, polycythaemia does not cause serious problems, although treatment may occasionally be necessary if the red cell count is so high that the blood becomes excessively viscous.
Macrocytosis (Enlarged Red Blood Cells)
Macrocytosis refers to red blood cells that are larger than normal. It is very common in newborns with Down syndrome and persists throughout life in approximately two thirds of individuals. It is not expected to cause any adverse medical effects.
Thrombocytopaenia (Low Platelet Count)
Thrombocytopaenia is a reduction in the number of platelets in the blood and is a common diagnosis in children with Down syndrome. A low platelet count may place an individual at risk of bleeding. Patients with severely reduced platelet counts may require platelet transfusions.
Thrombocytosis (Elevated Platelet Count)
Thrombocytosis refers to an elevated platelet count. It is rare in newborns with Down syndrome and, when it does occur, it typically causes no medical problems and resolves spontaneously within the first few weeks of life.
Leucopaenia (Low White Blood Cell Count)
Leucopaenia is a reduction in white blood cell count, which tends to fall below normal limits in approximately one third of people with Down syndrome. There is some concern that this may increase susceptibility to infection, although this association has not yet been clearly established in medical research.
Leukaemoid Reaction (Markedly Elevated White Blood Cell Count)
A leukaemoid reaction is a significant elevation in the white blood cell count. It can occur in infants with Down syndrome during the first few months of life. The condition usually resolves spontaneously, though in some cases it may be associated with a more serious underlying medical condition.
Transient Myeloproliferative Disorder (TMD)
Transient myeloproliferative disorder is a condition that occurs almost exclusively in newborns with Down syndrome and results from the rapid proliferation of abnormal white blood cells. It is estimated that 10–20% of infants with Down syndrome are diagnosed with TMD. The abnormal cells may resolve without treatment or may require intervention, with the decision based on the presence of specific harmful features in the individual child.
Treatments that have been used include leukapheresis (filtering abnormal cells from the blood) and chemotherapy (anti-cancer drugs). In the majority of cases, the prognosis for TMD is favourable, with complete resolution of the condition without any treatment. However, a small number of patients do not improve and go on to develop leukaemia, which may emerge years after apparent recovery from TMD. Given the potential for malignant progression, children diagnosed with TMD must be closely monitored for years following the resolution of signs and symptoms.
Oncological Conditions in Down Syndrome
Individuals with Down syndrome are at increased risk of developing pre-cancerous conditions such as myelodysplastic syndrome (MDS), potentially malignant conditions such as transient myeloproliferative disorder, and cancerous conditions such as leukaemia.
Myelodysplastic Syndrome (MDS)
Myelodysplastic syndrome is a pre-cancerous condition originating in the bone marrow. It is suspected when bone marrow blood cells begin to show abnormal changes, including a low platelet count, enlarged red blood cells, anaemia (a reduced red blood cell count and haemoglobin level), or an abnormal white blood cell count. If untreated, MDS may progress to leukaemia over a period of months to years. Assessment and management should be discussed with a haematologist or oncologist.
Leukaemia
Leukaemia is a cancer of the blood cells that develops when abnormal immature cells — known as "blast cells" — outnumber normal bone marrow cells and spread into the bloodstream. Blast cells may also spread to the brain, spinal cord, and other organs. Any patient diagnosed with leukaemia should be evaluated by a haematologist or oncologist to determine the specific subtype and appropriate treatment.
Cancer Treatment in People with Down Syndrome
People with Down syndrome tend to be more sensitive to certain chemotherapy agents, and some side effects may be more pronounced in this population compared to others. As such, closer monitoring is required when administering specific types of chemotherapy.
Other Cancers in Down Syndrome
People with Down syndrome may be at increased risk of developing germ cell tumours — a rare type of cancer that may arise in the ovaries or testes, or in other locations such as the brain, chest, or abdomen. There is also growing concern that retinoblastoma (a rare cancer that develops in the cells of the retina) may be diagnosed at higher rates among individuals with Down syndrome. Currently, however, leukaemia remains the most prevalent form of cancer in this population.
Source: Information in this section has been reproduced under an exclusive agreement with the National Down Syndrome Society (NDSS). Available at: www.ndss.org
