Macrocytosis is the enlargement of red blood cells with near-constant hemoglobin concentration, and is defined by a mean corpuscular volume (MCV) of greater than 100 femtolitres (the precise criterion varies between laboratories). The enlarged erythrocytes are called macrocytes or megalocytes (both words have roots meaning "big cell"). As a symptom its cause may be relatively benign and need no treatment or it may indicate a serious underlying illness. Causes
In humans, most commonly (especially when the increase in size is mild, and just above normal range) the cause is bone marrow dysplasia secondary to alcohol use disorder. Poor absorption of vitamin B12 in the digestive tract can also cause macrocytosis. Gastrointestinal diseases that may cause macrocytosis include celiac disease (severe sensitivity to gluten from wheat and other grains that causes intestinal damage) and Crohns disease (inflammatory bowel disease that can affect any part of the gastrointestinal tract). Other causes may include:

megaloblastosis (vitamin B12 or folate deficiency) because slowly dividing erythrocytes accumulate cytoplasmic components, resulting in larger-than-normal cells. hypothyroidism
chronic obstructive pulmonary disease (COPD)
aplastic anemia
reticulocytosis (commonly from hemolysis or a recent history of blood loss). liver disease because of an increase in circulating phospholipids and cholesterol, which bind on erythrocytes and induce membrane expansion
myeloproliferative disease
myelodysplastic syndrome which most commonly presents with macrocytic anemia
chronic exposure to benzene
pregnancy (most common, and requires no treatment as the person affected will return to normal post-partum)
Certain anti-inflammatory drugs, e.g. salazopyrin, azathioprine. Complications
No complications arise from macrocytosis itself and a prognosis will be determined from its cause. See also
Macrocytic anemia

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Meatal stenosis, making it more difficult or even impossible to urinate, may also occur.On the non-genital skin, the disease may manifest as porcelain-white spots with small visible plugs inside the orifices of hair follicles or sweat glands on the surface. Thinning of the skin may also occur. Psychological effect
Distress due to the discomfort and pain of lichen sclerosus is normal, as are concerns with self-esteem and sex. Counseling can help.According to the National Vulvodynia Association, which also supports women with lichen sclerosus, vulvo-vaginal conditions can cause feelings of isolation, hopelessness, low self-image, and much more. Some women are unable to continue working or have sexual relations and may be limited in other physical activities. Depression, anxiety, and even anger are all normal responses to the ongoing pain LS patients experience. Pathophysiology
Although it is not clear what causes LS, several theories have been postulated. Lichen sclerosus is not contagious; it cannot be caught from another person.Several risk factors have been proposed, including autoimmune diseases, infections and genetic predisposition. There is evidence that LS can be associated with thyroid disease. Genetic
Lichen sclerosus may have a genetic component. A high correlation of lichen sclerosus has been reported between twins and between family members. Autoimmunity
Autoimmunity is a process in which the body fails to recognize itself and therefore attacks its own cells and tissue. Specific antibodies have been found in LS. Furthermore, there seems to be a higher prevalence of other autoimmune diseases such as diabetes mellitus type 1, vitiligo, alopecia areata, and thyroid disease.