Research Techniques Made Simple: Genome-Wide Homozygosity/Autozygosity Mapping Is a Powerful Tool for Identifying Candidate Genes in Autosomal Recessive Genetic Diseases

Homozygosity mapping (HM), also known as autozygosity mapping, was originally used to map genes underlying homozygous autosomal recessive Mendelian diseases in patients from closely genetically related populations, followed by Sanger sequencing. With the increase in use of next-generation sequencing approaches, such as whole-exome sequencing and whole-genome sequencing, together with advanced bio-informatics filtering approaches, HM is again emerging as a powerful method for the identification of genes involved in disease etiology. In addition to its usefulness for research, HM is effective in clinical genetic services, increasing the efficiency of molecular diagnostics. For autosomal recessive Mendelian disorders with extensive genetic heterogeneity, HM can reduce both cost and turnaround time of mutation detection in the context of next-generation sequencing and can obviate expensive screening, such as biochemical testing in the setting of metabolic genodermatoses or antigen mapping for epidermolysis bullosa. It is therefore important for dermatology clinicians and researchers to understand the processes, principal uses, and advantages and limitations of HM when ordering or performing genetic tests for patients affected by heritable skin disorders.