الفهرس 
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Abstract
Alopecia areata is a common type of hair loss. The pathophysiology of AA is considered to be T-cell mediated autoimmunity that occurs mostly in genetically predisposed individuals. In addition to disturbance of immune function, complex interactions between predisposing genetic and environmental factors act as triggers for disease progression. Perifollicular nerves and vasculature, viruses, trace element alterations, endocrine disorders, and thyroid dysfunction have been also hypothesized.
Folic acid has received particular attention in recent years as this vitamin has been shown to have an unexpected and crucial effect on the immune response.
Folic acid has been reported to exhibit different immunological activities such as its deficiency inhibits the activity of CD8+T cells and reduces the proliferative responses of lymphocytes and natural killer cell activity. Additionally, folate receptor 4 (FR4) is both a marker of Treg cells and is immunologically functional in the maintenance of Treg cells. In the absence of folic acid, naive Tcells can differentiate into Treg cells, but differentiated Treg cells fail to survive owing to the decreased expression of anti-apoptotic molecules (Bcl -2).
The relationship between folate deficiency and hair loss has been examined in several studies, some of which suggest that folate deficiency affect the cells of the hair follicles in two ways. First, the decline in cell metabolism means that these cells cannot keep up the rate of hair production. Hair follicle cell division and growth are reduced especially when the cells are not adequately suffused with oxygen and nutrients. Not only the hair strands but also the scalp is affected. Other cells such as papilla and oil-secreting cells will also be affected. This leads to a fall in the production of new hairs, graying hair as well as a sharp rise in the number of hair strands falling off.
Secondly, the anemia caused by folic acid deficiency is closely related to the one caused by iron deficiency. This means that the cells will turn to alternative sources of energy when the nutrients and oxygen for the production of ATP are diminished. One of these alternative energy sources is testosterone. With increased production of testosterone is an associated rise in its conversion to DHT which is known to cause androgen-related hair loss. Therefore, folic acid deficiency starts a series of interrelated adverse effects which all leads to hair loss.
Lack of folate is highly involved with the methylation process and MTHFR genes. Gene alterations with DNA methylation at the MTHFR gene C677T and other genes involved with the methylation process were linked with autoimmune hair loss.
The development of AA may also be associated with high levels of homocysteine or some of its metabolites. Homocysteine appears to exert diverse effects on immune function in the circulation and within the tissue microenvironment possibly contributing to age-related immune dysfunction and disease pathology.
In the present study, the aim was to evaluate the levels and clinical significance of RBCs folate in patients with alopecia areata. The patients were selected from Dermatology, Venereology and Andrology Outpatient Clinic of Zagazig University Hospitals during the period from November 2015 till April 2016. The thirty four AA patients involved in this study and thirty four age and sex matched healthy controls were checked for their RBCs folate level (to determine if folate deficiency contribute to development of AA).
The thirty four AA patients involved in the present study had mean age of (27.24 ± 14.48) years. They included 21 males (61.8 %) and 13 females (38.2%).
Analysis of family history of the studied cases has revealed that family history of AA was positive in 3 cases (8.8%) and negative in 31 cases (91.2%).
This study showed that patients with AA had mean RBCs folate level of (210± 53.4)µg/dl, while controls had mean level of (306.85± 32.78) µg/dl, with significant difference between patients and controls as p. Value was < 0.001.
Also we found that RBCs folate level did not show any significant variations with respect to the sex, number of the lesions or the grade of severity either mild, moderate or severe types.