G004 Genetic counselling in Huntington disease: think at an additional genetic condition!

<h3>Background</h3> Huntington Disease (HD) is an autosomal dominant (AD) disease with a risk of 50% to the offspring. Most of genetic counselling includes diagnosis, predictive, prenatal and preimplantation genetic testing of this isolated condition. <h3>Aims</h3> with the access to new DNA technologies, additional genetic rare diseases are shown in HD patients and/or in their family members with more complexity of genetic counselling. A careful clinical and neurological examination, extended family history, metabolic analysis, chromosomal microarray analysis, DNA Shallow Whole Genome Sequencing, single gene, multigene panel and Next Generation Sequencing are used for a precise diagnosis in HD families. <h3>Results</h3> Five HD families are described with at least one additional genetic condition: Malignant hyperthermia susceptibility (OMIM 145600, AD) with a pathogenic variant of RYR1 and an infantile-onset Pompe disease (OMIM 232300, AR) has occured. Autosomal recessive (AR) spastic paraplegia 5A (OMIM 270800, AR) caused by compound heterozygous variant in the CYP7 B1 gene. Episodic Ataxia type 2 (OMIM 108500, AD) with pathogenic variant of CACNA1A, Intellectual development disorder-6 due to GRIN2B pathogenic variant (OMIM 613970, AD). Microdeletion in 15q11.2 which could explain some intellectual or psychiatric difficulties. <h3>Conclusion</h3> occurence of rare and very rare diseases with HD is underestimated. Attention should be paid to find an additional genetic condition which could explain unusual HD symptoms. In these cases, complexity of genetic counselling has to be recognised and psychosocial support should be recommended.