Megaloblastic<unk> s Megaloblastic<unk> s represent a type of<unk>  characterized by certain morphologic abnormalities noted on a peripheral blood smear examination. These abnormalities include the presence of enlarged oval shaped red blood cells (macroovalocytes) and hypersegmented neutrophils (defined as a neutrophil with six or more lobes). Hypersegmented neutrophils may be seen in the absence of macroovalocytes as hypersegmentation of neutrophils is an early sign of megaloblastic<unk>  and may precede the appearance of macroovalocytes; they may also be seen in other<unk> s (e.g., iron deficiency<unk>  and thus are suggestive of megaloblastic<unk>  but not specific for it. An increased red cell distribution width (anisocytosis) also suggests megaloblastosis and is commonly seen in Vitamin B12 deficiency and folic acid deficiency. This type of<unk>  is caused by impaired DNA synthesis and repair, often from deficient thymidine production. Thiamine responsive megaloblastic<unk>  syndrome also causes megaloblastic<unk> . The red blood cells grow larger because they cannot produce DNA quickly enough to divide at the right time as they grow and thus grow too large before division. Additional causes of megaloblastic<unk>  include medications that interfere with DNA synthesis or with the absorption or metabolism of Vitamin B12 or folate such as methotrexate, sulfasalazine, metformin, anticonvulsant medications (e.g., valproic acid or phenytoin), certain antibiotics (e.g., trimethoprim/sulfamethoxazole), antiretroviral medications, cholestyramine, triamterene, and nitrous oxide. Non-Megaloblastic<unk> s Red cell membrane disorders producing codocytes Other disorders which cause macrocytosis without DNA replication problems (i.e., non-megaloblastic<unk> s), are disorders associated with increased red cell membrane surface area, such as pathologies of the liver and spleen which produce codocytes or "target cells" which have a central collection of hemoglobin surrounded by a pallor (a thin area) then followed by a thicker collection of hemoglobin at the rim of the cell. Alcohol Round macrocytes which are not codocytes are produced in chronic alcoholism (which produces a mild macrocytosis even in the absence of vitamin deficiency), apparently as a direct toxic effect of alcohol specifically on the bone marrow. Excessive alcohol consumption is one of the most common causes of macrocytosis and non-megaloblastic<unk> . Association with rapid red cell turnover and reticulocytosis Mild macrocytosis is a common finding associated with rapid blood restoration or production, since in general, "fresh" or newly produced red cells (reticulocytes) are larger than the mean (average) size, due to slow shrinkage of normal cells over a normal red cell circulating lifetime. Thus, chronic obstructive pulmonary disease (COPD), in which red cells are rapidly produced in response to low oxygen levels in the blood, often produces mild macrocytosis. The macrocytosis associated with COPD is also attributed to excess cell water secondary to carbon dioxide retention. Also, rapid blood replacement from the marrow after a traumatic blood loss, or rapid red blood cell turnover from rapid hemolysis (G6PD deficiency), also often produces mild macrocytosis in the associated<unk> .
Macrocytic anemia
Lycopenemia
Plasmacytosis
Reticulocytosis
Neutrophilia
Microcytic anemia
Microhematuria
Hepatosplenomegaly