Novel homozygous variants in ATCAY, MCOLN1, and SACS in complex neurological disorders

Neurological disorders comprise a large group of clinically and genetically heterogeneous disorders, many of which have a genetic cause. In addition to a detailed neurological examination, exome sequencing is being increasingly used as a complementary diagnostic tool to identify the underlying genetic cause in patients with unclear, supposedly genetically determined disorders.

To identify the genetic cause of a complex movement disorder in five consanguineous Pakistani families.

We included five consanguineous Pakistani families with complex recessively inherited movement disorders. Clinical investigation including videotaping was carried out in a total of 59 family members (4-21 per family) and MRI in six patients. Exome sequencing was performed in 4-5 family members per pedigree to explore the underlying genetic cause.

Patients presented a wide spectrum of neurological symptoms including ataxia and/or dystonia. We identified three novel homozygous, segregating variants in ATCAY (p.Pro200Profs*20), MCOLN1 (p.Ile184Thr), and SACS (p.Asn3040Lysfs*4) in three of the families. Thus, we were able to identify the likely cause of the disease in a considerable number of families (60%) with the relatively simple and nowadays widely available method of exome sequencing. Of note, close collaboration of neurologists and geneticists was instrumental for proper data interpretation.

We expand the phenotypic, genotypic, and ethnical spectrum of mutations in these genes. Our findings alert neurologists that rare genetic causes should be considered in complex phenotypes regardless of ethnicity.