What is ARMC9? What happens when ARMC9 has a defect?
ARMC9 is a gene present in our genome. We have two copies of ARMC9, one that comes from paternal side (father) and other comes from maternal side (mother). ARMC9 has an important role in development of brain and eye. Presence of mutation (change or defect)  in both the copies of ARMC9 (coming from father and mother both) causes Joubert Syndrome 30 (JS30). The child has intellectual disability, developmental delay, eye defect (mostly ptosis), polydactyly (extra finger) due to presence of defect in ARMC9 gene.

How to detect Joubert Syndrome 30 related to mutation in ARMC9 gene?
Child with delayed development, intellectual disability, ptosis, polydactyly should be observed carefully under expert clinical geneticist. The brain – MRI of affected individuals shows “molar tooth sign”, which is a classical indication of Joubert syndrome. Further diagnosis is confirmed by performing genetic testing in an affected individual, that enables the detection of pathogenic variants (disease causing changes) in ARMC9 gene.

For identifying genetic changes in ARMC9 gene, one can opt for direct sequencing of ARMC9 gene by Sanger sequencing or by whole exome sequencing. The genetic test can be performed on blood or saliva sample from affected individual (sometimes parents also for confirmation).