Primary Microcephaly and Schizophrenia: Genetics, Diagnostics and Current Therapeutics

Intellectual disabilities (ID) are among the most common genetic disabilities worldwide. Over the last two decades, ID has especially drawn special scientific interest being the key to understanding normal brain development, growth, and functioning. Here, we discuss two intellectual disabilities to better understand the emerging trends in disease diagnosis as well as the therapies available for their management. Primary microcephaly (MCPH) is a monogenic genetic disorder with twenty-eight loci (MCPH1-MCPH28) mapped so far with all the causative genes being elucidated as well. The role of these genes in disease prognosis along with their association with various MCPH-linked phenotypes plays an important role in the molecular diagnosis of the disease. As there is no cure/treatment yet available to enlarge a congenitally small brain, management modalities in use include physical, speech and occupational therapies as well as psychological and genetic counselling to not only reduce the incidence of the disorder but also to help families cope better. The second intellectual disability being discussed here is schizophrenia which is a multifactorial disorder owing to its complex and extremely heterogeneous etiology. Although various environmental factors play an important role, the genetic factors have been identified to play the most pivotal role in disease presentation as to date, 19 loci (SCZD1-SCZD19) have been linked to schizophrenia. However, underlying genes for only six of these loci have been mapped along with 10 other genes that are either linked to schizophrenia or show susceptibility to it. Diagnosis of schizophrenia needs careful consideration and various tests and tools currently employed for complete diagnosis have been discussed here. The management options for schizophrenia include pharmacological, non-pharmacological and intracranial therapies. These disorders shed light on the important role omics technologies have played not only in better understanding of the disease prognosis but also assisting in disease diagnosis and treatment modalities too. 

Keywords: Cortical development, Dopamine pathways, Genetic heterogeneity, Genotype-phenotype associations, Occipitofrontal head circumference (OFC), Primary microcephaly (MCPH), Schizophrenia.