Alopecia areata (AA) is a chronic inflammatory condition causing non-scarring type of hair loss that can affect any hair bearing area. It shows a spectrum of severity that ranges from patchy localized hair loss, which can eventually involve the entire scalp (a condition known as alopecia totalis), to the complete absence of hair everywhere on the body (a condition known as alopecia universalis). Unpredictable hair loss is the only noticeable symptom of this disease. However, characteristic nail changes may also associated with hair loss. Patients may recover spontaneously but the disease can follow a course of recurrent relapses or result in persistent hair loss. The age of onset of the disease can be sudden at any age, varying from birth to 80 years; however, the majority (60%) commence before 20 years of age. There is equal distribution of incidence across races and sexes. Alopecia areata may be associated with Down's syndrome and other autoimmune conditions, such as thyroid disease and vitiligo. The lifetime risk of developing the condition has been estimated at 1.7%, making it one of the most common human autoimmune diseases.
Diagnosis is usually made clinically, although a biopsy is diagnostic for this condition. Treatment of this condition aims to the re-growth of hair in affected individuals. Many treatments exist for AA including: intralesional corticosteroid injections, which are widely used in mild disease, topical anthralin, minoxidil, and topical sensitizers, such as squaric acid dibutlyester and diphenyl-cyclopropenone. However, none of these treatments alter the natural history of the disease. On the other hand, there is a high proportion of spontaneous recovery, with 34% to 50% of the patients recovering within 1 year; therefore, not all patients require treatment. Poor prognosis is linked to the presence of other immune diseases, family history of AA, young age at onset, nail dystrophy, extensive hair loss, and ophiasis (AA of the scalp margin). The unpredictable nature of the condition, with apparent improvement followed by deterioration can be causing great psychological distress. Hence, one of the most important aspects of management is counseling the patient and the family members of a young child about the nature and course of the condition as well as the available effective treatments with details of what they involve and their side effects.
Although the exact etiology of alopecia areata is not known, the pathophysiology of it is considered to be T-cell mediated autoimmunity in which the immune system mistakenly attacks the hair follicles that occurs mostly in genetically predisposed individuals. Approximately 20% of affected individuals have a family history of the disease, demonstrating that AA has a genetic component. Multiple loci have been associated with the AA disease which are chromosome 21 (increased incidence in Down's syndrome), major histocompatibility complex, and cytokine and immunoglobulin genes, indicating a polygenic basis. In addition, environmental factors could act as triggers for disease progression in genetically predisposed individuals.