Joint Hypermobility as a Potential Indicator of Marfan Syndrome and Ehlers-Danlos Syndrome.

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder associated with the mutation of the FBN1 gene. Ehlers-Danlos syndrome (EDS) is a group of inherited connective tissue disorders with similar clinical features to MFS that often requires genetic testing to confirm a diagnosis of an EDS subtype. MFS is diagnosed using the Ghent Nosology criteria, which screens for cardiovascular, musculoskeletal, integumentary, ocular, and pulmonary abnormalities. Though genetic testing has recently been increasingly emphasized in diagnosing MFS, it is not currently a mandatory component of the Ghent Nosology. We present the case of a nine-year-old male who presented with joint hypermobility of the shoulders, knees, and thumbs, and a family history of joint hypermobility in his 15-year-old brother. Genetic testing ruled out MFS, and the patient subsequently underwent testing for EDS, which further ruled out classical and hypermobile EDS. This case highlights the importance of supplementing the Ghent Nosology criteria with genetic testing in diagnosing MFS because it can aid in generating a differential diagnosis and optimizing diagnostic accuracy.