TY - JOUR T1 - Lessons of the month 3: Mosaic Klinefelter syndrome unveiled by acute vertebral fracture in a middle-aged man JF - Clinical Medicine JO - Clin Med SP - e420 LP - e422 DO - 10.7861/clinmed.2021-0348 VL - 21 IS - 4 AU - Aye Chan Maung AU - Jenny YC Hsieh AU - David Carmody AU - Swee Du Soon Y1 - 2021/07/01 UR - http://www.rcpjournals.org/content/21/4/e420.abstract N2 - 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. ER -