P28 Marfan syndrome? Think again

Abstract Background A 21 year old male was referred to the adult hypermobility clinic from the local rheumatologist with a suspected diagnosis of Marfan syndrome, based on his body habitus although he had presented to his GP with painful toes. Methods He had a background of autism,learning difficulties and was wearing glasses due to amblyopia. He had a history of dental crowding with two previous teeth extractions. There was no family history of note. On examination, his arm span was not greater than his height, there was no arachnodactyly, his palate was normal, but he had gum hypertrophy. His skin texture was normal, with no abnormal scarring or bruising, but there was presence of striae. His Beighton score was 4/9 and he had flat feet. There was reduced muscle mass and hypotonia, which was felt to be the cause of his hypermobility, rather than increased ligamentous laxity. There was evidence of gynaecomastia and lack of facial hair. The working diagnosis was Klinefelter syndrome due to his tall stature, gynaecomastia and absence of secondary male characteristics. Subsequently, the patient was referred to endocrinology and for genetic testing. Results The endocrinology team recognised the clinical features of male hypogonadism with small phallus (Tanner stage 2/3) and small testes, confirmed also by ultrasound. The patient reported absence of early morning erections. Blood tests confirmed hypergonadotropic hypogonadism (high luteinizing hormone, low testosterone) and the patient was commenced on testosterone therapy. His bone mineral density values lied within the expected range for age. Karyotype analysis confirmed the presence of 48,XXYY which is a chromosomal condition characterized by the presence of an extra X and Y chromosome in males. In terms of management, he attended our Outpatient Hypermobility Exercise Programme and was given advice on footwear. He was provided with extensive written information about this condition by the Rare Chromosome Disorder Support Group, Unique. Conclusion Our case report illustrates the importance of considering 48,XXYY syndrome in patients with typical body habitus and joint hypermobility. Marfanoid habitus is associated with connective tissue diseases, like hypermobile Ehlers-Danlos syndrome and Marfan syndrome, but also described in homocystinuria and Klinefelter syndrome. 48,XXYY was considered previously as a variant of Klinefelter syndrome, but now it is regarded as a separate syndrome with overlapping features