In individual DMD patients, a single exon deletion was detected by the MLPA method for DMD exons, yet the results were verified by a generation sequencing test without the exon deletion. The patient’s family began to doubt the test results and even the doctor’s diagnosis. The clinician’s diagnosis is based on clinical manifestations, and all other tests, including genetic testing, are only “aids” to the diagnosis. These aids are good “weapons” for clinicians to diagnose diseases. However, there are limitations to the use of all these “weapons”. Clinicians must understand the performance of these “weapons”. MLPA combines DNA probe hybridization and PCR technology and has the following advantages: 1. High efficiency: 45 target sequence copy number changes can be detected in one reaction. 2.Specific: it can detect point mutations. 3, rapid: one experiment can be completed within 24 hours. 4.Simple: the operation of different kits is basically the same and easy to master. The MLPA technique has the following limitations: 1, requires precise measurement of DNA concentration, and the sample is easily contaminated. 2.It cannot be used for the detection of individual cells. 3, MLPA is used to detect deletion or duplication of genes and is not suitable for detecting unknown point mutation types. 4.It cannot detect balanced translocations of chromosomes.