alopecia areata ( aa ) is a chronic inflammatory disease of the hair follicles and nails , its etiology is unknown , probably multifactorial with evident autoimmune and genetic components . the first clinical description of aa is attributed to celsus ( 14 - 37 b.c . ) and the designation aa was given by sauvages .
the importance of genetic factors in aa is underlined by the high frequency of a positive family history in affected individuals . in most reports , these range from 10% to 20% of cases .
a study in monozygotic and dizygotic pairs found a concordance rate of 55% for alopecia amongst monozygotic twins with no concordance among the dizygotic pairs . though it can affect any age group , demographical data on aa is still lacking .
two brothers aged 5 and 7 years presented to the outpatient department with complaints of asymptomatic patchy loss of scalp hair for the past 2 and 4 months respectively .
there was no similar complaint in any other family member , siblings and no history suggestive of systemic involvement , drug intake , trauma , pus filled lesions or any other skin eruptions .
mucocutaneous examination revealed multiple smooth patches of alopecia ranging from 2 cm  2 cm to 4 cm  6 cm over occipital and vertex area of elder child and multiple patches over occipital and temporal region measuring 2 cm  2 cm to 2 cm  4 cm of the younger one [ figure 1a and b ] .
( a ) multiple areas of nonscarring alopecia involving the occipital and vertex area in a 7-year - old child ( b ) multiple areas of nonscarring alopecia involving the occipital and temporal area in sibling 5-year - old surface of the patches was smooth with no apparent changes .
histopathological examination of the biopsy sample from the alopecia patch from the scalp confirmed the diagnosis , which showed inflammatory infiltrate in and around the bulbar region of hair follicle .
alopecia areata is t cell mediated autoimmune disease with genetic predisposition resulting in partial and total nonscarring alopecia .
scalp is the predominant site of involvement with the most common clinical pattern involving multiple areas of patchy hair loss .
most patients develop aa before the age 40 years with 11 - 20% of all cases occurring in children .
the ratio of male : female in aa in pediatric age group is 1:1 where as in adolescent and adult it is more common in female .
human leukocyte antigen ( hla)-dq3 and hla - dqb1fnx0103 alleles appear to be marker for genetic susceptibility to aa with the latter serving as a special genetic marker for more severe variants .
the diagnostic pathologic feature is peribulbar lymphocytic inflammation ( swarm of bees ) predominately cd4 + cells along with cd8 + t cells affecting anagen follicles or follicles in early catagen .
short , easily extractable broken hairs , known as exclamation mark hairs , are often seen at the margins of the bald patches during active phases of the disease .
the scalp is the first affected site in most cases , but any hair - bearing skin can be affected .
the term alopecia totalis is applied to total or almost total loss of scalp hair , and alopecia universalis is the loss of all body hair .
children with aa demonstrate an increased levels of activated t cells leading to various autoimmune diseases like vitiligo , thyroiditis , connective tissue disorders , lichen planus , type 1 diabetes , and pemphigus foliaceous .
geometric and superficial pits are typical of aa whereas deep and irregularly distributed pits are seen in psoriasis and atopic dermatitis . familial aggregation of aa has been studied and it has been found that estimated lifetime risk has been 7.1% in siblings , 7.8% in parents , 5.7% in offspring .
aa has been also reported after allogenic bone marrow transplantation from an affected , hla matched sibling .
menon and kiran reported a case of concomitant occurrence of aa in the sibling with emphasis on environmental precipitating factors .
evidence based management of aa in children is limited due to the lack of well controlled randomized studies .
reassurance should be given to patients with limited disease as spontaneous remission occurs in 80% of patients .
various treatment options tried in aa are topical , intralesional , and systemic corticosteroids , topical immunomodulators , and topical irritants like dithranol , psoralen plus ultraviolet a therapy , excimer laser therapy .
 alopecia areata ( aa ) is a t cell mediated autoimmune disease with multifactorial etiology resulting in partial and total nonscarring alopecia . 
 we hereby report a case of two brothers ( aged 7 and 5 years ) presenting with coincidental aa over scalp which is a rare presentation . 