%0 Journal Article %A Aye Chan Maung %A Jenny YC Hsieh %A David Carmody %A Swee Du Soon %T Lessons of the month 3: Mosaic Klinefelter syndrome unveiled by acute vertebral fracture in a middle-aged man %D 2021 %R 10.7861/clinmed.2021-0348 %J Clinical Medicine %P e420-e422 %V 21 %N 4 %X Klinefelter syndrome (KS) is the most common sex chromosome disorder in males. It is the result of two or more X chromosomes in a phenotypic male. In addition to primary hypogonadism affecting male sexual development, it is associated with a series of comorbidities such as osteoporosis, psychiatric and cognitive disorders, metabolic syndromes, and autoimmune diseases. A broad spectrum of phenotypes has been described and many cases remain undiagnosed throughout their lifespan. In this case report, we describe a case of mosaic KS unmasked by acute vertebral fracture. %U https://www.rcpjournals.org/content/clinmedicine/21/4/e420.full.pdf