A Next Generation Sequencing custom gene panel as first line diagnostic tool for atypical cases of syndromic obesity: Application in a case of Alström syndrome

Abstract

Obesity phenotype can be manifested as an isolated trait or accompanied by multisystem disorders as part of a syndromic picture. In both situations, same molecular pathways may be involved to different degrees. This evidence is stronger in syndromic obesity, in which phenotypes of different syndromes may overlap. In these cases, genetic testing can unequivocally provide a final diagnosis. Here we describe a patient who met the diagnostic criteria for Alström syndrome only during adolescence. Genetic testing was requested at 25 years of age for a final confirmation of the diagnosis. The genetic diagnosis of Alström syndrome was obtained through a Next Generation Sequencing genetic test approach using a custom-designed gene panel of 47 genes associated with syndromic and non-syndromic obesity. Genetic analysis revealed a novel homozygous frameshift variant p.(Arg1550Lysfs*10) on exon 8 of the ALMS1 gene. This case shows the need for a revision of the diagnostic criteria guidelines, as a consequence of the recent advent of massive parallel sequencing technology. Indications for genetic testing reported in these currently accepted diagnostic criteria for Alström syndrome, were drafted when sequencing was expensive and time consuming. Nowadays, Next Generation Sequencing testing could be considered as first line diagnostic tool not only for Alström syndrome but, more generally, for all those atypical or not clearly distinguishable cases of syndromic obesity, thus avoiding delayed diagnosis and treatments. Early diagnosis permits a better follow-up and pre-symptomatic interventions.

Keywords: ALMS1; Alström syndrome; NGS; Obesity.