From MedlinePlus Genetics
5q minus (5q-) syndrome is a type of bone marrow disorder called myelodysplastic syndrome (MDS). MDS comprises a group of conditions in which immature blood cells fail to develop normally, resulting in too many immature cells and too few normal mature blood cells. In 5q- syndrome, development of red blood cells is particularly affected, leading to a shortage of these cells (anemia). In addition, the red blood cells that are present are unusually large (macrocytic). Although many people with 5q- syndrome have no symptoms related to anemia, especially in the early stages of the condition, some affected individuals develop extreme tiredness (fatigue), weakness, and an abnormally pale appearance (pallor) as the condition worsens. Individuals with 5q- syndrome also have abnormal development of bone marrow cells called megakaryocytes, which produce platelets, the cells involved in blood clotting. A common finding in people with 5q- syndrome is abnormal cells described as hypolobated megakaryocytes. In addition, some individuals with 5q- syndrome have an excess of platelets, while others have normal numbers of platelets.

MDS is considered a slow-growing (chronic) blood cancer. It can progress to a fast-growing blood cancer called acute myeloid leukemia (AML). Progression to AML occurs less commonly in people with 5q- syndrome than in those with other forms of MDS.  https://medlineplus.gov/genetics/condition/5q-minus-syndrome