Down syndrome (DS) is a genetic disorder caused by the presence of a third copy of chromosome 21.It is usually associated with physical growth delays, mild to moderate intellectual disability, and characteristic facial features .Children with DS are at an elevated risk of leukemia, especially myeloid leukemia. On the other hand, children with DS are at a 20-fold increased risk for acute lymphoblastic leukemia (ALL).In our case, we presented a patient with DS who was diagnosed with ALL.

19-year-old male was admitted to the emergency department due to abdominal pain.On his physical examination,splenomegaly was detected.In laboratory examinations; kidney and liver function tests were normal,lactate dehydrogenase:372 U/L,uric acid: 5.4 mg/dl,white blood cell:25000 × 106/L,lymphocyte: 15780 × 106/L, neutrophil:1140 × 106/L,hemoglobin:10 gr/dl, thrombocyte:12000 × 106/L,coagulation tests were normal and in peripheral blood smear evaluation,90% blast cells were detected.

Peripheral blood flow cytometry evaluation was compatible with B-ALL(TdT,CD19,CD10,CD34,cCD79a,CD58,CD9,CD38,CD123,CD20,CD81,CD22 positivity in atypical cells).Bone marrow biopsy was hypercellular.There was diffuse blastic cell infiltration,which stained extensively with TDT,CD79a.Chromosomal analysis is 47XY,+21 and t(12,21) (p13.2;q22.12) (ETV6/RUNX1) (FISH) and 14q32.33 (IGH) FISH were positive,t(9;22) P190 -p210,t(4;11), t(1;19),11q23 were negative.The risk classification was standard risk.

AUGMENTED BFM induction chemotherapy protocol was started.Pancreatitis was developed after peg-asparaginase and chemotherapy-related hepatotoxicity(grade 1) was developed.Central nervous system prophylaxis(intrathecal methotrexate) was applied.The control bone marrow biopsy performed after induction was normocellular,the blast rate was <5%.BFM standard risk first consolidation chemotherapy protocol was started.He died of septic shock on the eighteenth day of the first consolidation treatment.

Cases of DS-ALL cases are at greater risk for serious side effects from chemotherapeutics,mortality and recurrence than non DS-ALL.Because children with DS have a higher incidence of treatment-related toxicity,survival rates are lower than non-DS children.During ALL induction chemotherapy life-threatening side effects are tumor lysis syndrome,thrombosis,bleeding and infection.In the UKALL 2003 study,DS associated with a significantly increased risk of death from sepsis during chemotherapy.