Myelodysplastic Syndrome (MDS) is marked by biological and clinical heterogeneity, characterized by dysplasia in the bone marrow and blood cells with the presence of cytopenias. MDS is recognized as a disease in elderly individuals. About 86% of MDS cases are diagnosed at age ≥ 60 and less than 10% of patients are younger than 50. Recurrent cytogenetic abnormalities are present in 40% to 60% of cases. Cytogenetic analysis plays an important role, whether in the diagnosis or classification of the disease. Recently, the new international molecular prognostic score system (IPSS-M) reinforces the valuable prognostic contribution of cytogenetics in MDS in both survival and leukemic evolution.

To report a chronic chloroform exposure as a trigger capable of inducing DNA damage.

Chronic exposure to a genotoxic agent has been linked to MDS chromosomal abnormality. Among these, chloroform, and an inorganic halide derivative of hydrocarbons can induce the DNA lesion. A 24-year-old male patient with a marked history of 10-year chloroform exposure sought medical attention for anemia, fainting, and unintentional weight loss. He was diagnosed with Myelodysplastic Syndrome and refractory anemia with excess blasts (RAEB II) with initial tests: Hb = 5 g/dL; neutrophils=320/mm3; platelets= 18 x 109/L. Bone marrow aspiration showed 15% myeloblasts, immunohistochemistry profile showed CD34+, CD117+ in blasts and cytogenetic analysis showed a very complex karyotype: 45,XY,del(6)(q22),-7,add(9) (q12),del(12)(p11.2),del(17)(p13),del(20)(q12),add(21(p13)[17]/46, XY[3]. Chemotherapy with azacitidine was performed as a bridge to bone marrow transplantation, but the patient evolved into sepsis, dying eight months after diagnosis.

The pathogenesis of MDS reflects the heterogeneity of the disease, thus, comprises multiple steps and includes factors that can be endogenous and/or exogenous. Therefore, this unusual case shows the extreme importance of investigating possible recurrent and/or occupational exposures in these patients combined with cytogenetics analyses.