duchenne muscular dystrophy ( dmd ) and its less severe allelic form becker muscular dystrophy ( bmd ) are x - linked recessive devastating neuromuscular disorder that affects 1 in 3,500 males births and is caused by mutations in the dystrophin gene . the frequency and distribution of deletion in dystrophin gene in dmd population from northeast india is reported in the present work . a total of 69 patients were enrolled in this prospective study with clinically suspected dmd , attending the neurology clinic at gauhati medical college hospital , guwahati , assam between october 2009 and september 2011 . the diagnosis of dmd was based on the clinical findings of progressive and characteristic pattern of proximal muscle weakness , calf pseudohypertrophy , positive gower 's sign , valley sign , electromyography ( emg ) , an elevated serum creatine kinase ( ck ) activity , and the transmission of the pattern as an x - linked trait . screening of deletions of the dystrophin gene were performed according to chamberlain et al . and beggs et al . , using two multiplex pcr assays allowing the amplification of total 17 exons : the chamberlain reaction using primers for exons 4 , 8 , 12 , 17 , 19 , 44 , 45 , 48 , 51 and the beggs reaction performed with primers for the promoter and exons 1 , 3 , 6 , 13 , 43 , 47 , 50 , and 52 . the pcr products were separated on 2% nusieve + 1% agarose minigels and the bands were visualized by staining with ethidium bromide . baseline patient characteristics were reported using the median or mean  sd for continuous variables according to their distribution . the families were divided in two groups according to the propositus multipex pcr analysis ( 13 deleted families and 6 non - deleted ) . wallis test for non - gaussian distributed continuous variables and chi - square analysis for categorical variables . screening of deletions of the dystrophin gene were performed according to chamberlain et al . and beggs et al . , using two multiplex pcr assays allowing the amplification of total 17 exons : the chamberlain reaction using primers for exons 4 , 8 , 12 , 17 , 19 , 44 , 45 , 48 , 51 and the beggs reaction performed with primers for the promoter and exons 1 , 3 , 6 , 13 , 43 , 47 , 50 , and 52 . the pcr products were separated on 2% nusieve + 1% agarose minigels and the bands were visualized by staining with ethidium bromide . baseline patient characteristics were reported using the median or mean  sd for continuous variables according to their distribution . the families were divided in two groups according to the propositus multipex pcr analysis ( 13 deleted families and 6 non - deleted ) . wallis test for non - gaussian distributed continuous variables and chi - square analysis for categorical variables . out of 69 patients of dmd , 40 ( 58% ) were from the hindu community and 29 ( 42% ) from the muslim community , with age ranging from 2 - 9 years . the mean age of onset was 1.72 + 0.69 years ( range 0.8 - 3 years ) and the mean age at presentation was 6.24 + 176 ( range 2 - 9 years ) . all boys presented with progressive proximal muscle weakness particularly of the lower limbs and the majority ( 75.3% ) complained of calf muscle pseudohypertrophy . a total of 49 ( 71% ) cases showed intragenic deletions , the localization of these deletions are shown in figure 1 . majority of the deletions ( 42/49 , 85.7% ) were located at distal hot spot region that encompasses exons 44 - 55 and 14.3% of the deletions were located at the proximal hot spot region ( exons 2 - 19 ) . representing the gene , the localization , and the frequencies of deletions in 49 patients a total of 130 exons ( 108 in isolated cases , 22 in familial cases ) were deleted in 49 patients , and the average number of exons deleted per patients was 2.9 . single exon was deleted in 19 patients ( 38.7% ) , and in 30 patients ( 61.3% ) multiple exonic deletions were seen . most frequent single exon deleted were 45 and 47 , the most common exons involved in multiple deletions were 48 ( 36.7% ) , 47 ( 40.8% ) , and 50 ( 42.8% ) . the most frequent exon deletion in overall deletions were 50 ( 14.38% ) , followed by 48 ( 13.6% ) , 49 ( 12% ) , and 47 ( 10% ) . largest deletions were present in 6 patients extending from exon 44 to 52 in 5 patients and from exon 8 to 43 in 1 patient . on comparison between the familial and isolated cases of dmd , deletions were found in 72% of isolated cases and 68.4% in familial cases . out of 19 cases with family history , single exon deletion was seen in 7 and multiple exon deletion ( upto 3 ) in 6 cases . a previous study reported approximately 3% higher detection rate in familial cases as compared to sporadic cases . contrary to this , our study have shown approximately 4% reduction in deletion rate in familial cases ( p = 0.0084 ) . it is difficult to draw a definite conclusion as our series had a small sample size . multiplex pcr methods allow detection of approximately 98% of deletions , which accounts for 65% of all mutations . locations of deletions in the dystrophin gene are apparently nonrandom with a preponderance found in two   hot spot regions at the 5 terminus and in the distal half of the central rod domain around exons 44 - 53 . the proportion of deletions in different populations of india shows a wide variation in the distribution . the reported frequency of deletion in various parts of india range from 62.1% to 74% using multiplex pcr , with which our data conforms . no particular reasons have been persuasively attributed to explain population - based differences in mutations of the dystrophin gene , it is presumed to be due to accumulation of differences in intronic sequences and their distribution over a time period as a consequence of genetic drift . such sequences unique to the population may favour intragenic deletions due to mismatch at the locus . in our study , 71% of patients showed deletions . in these patients , detection of dmd was done by deletion analysis using multplex pcr , hence eliminating the need to do muscle biopsy for diagnosis . as this disease has no effective therapy , early diagnosis of patient can be helpful for carrier detection and genetic counseling . with genetic counseling ,
duchenne muscular dystrophy ( dmd ) is an x - linked recessive disorder that affects 1 in 3,500 males and is caused by mutations in the dystrophin gene . in this paper , we have reported dna analysis of dmd patients by multiplex polymerase chain reaction ( pcr ) from various states of northeast india . of the 69 clinically suspected patients of dmd , deletion was detected by multiplex pcr in 49 ( 71% ) patients . 
 majority of the deletions ( 42/49 , 85.7% ) were located at distal hot spot region that encompasses exons 44 - 55 and 14.3% of the deletions were located at the proximal hot spot region ( exons 2 - 19 ) . in this study population , 
 the deletion rate was 71% and was more frequent in the distal end exon .