241Wolfram Syndrome (Wolfram症候群)
242Worster-Drought Syndrome (WDS)
243WWOX Syndrome (Genetic Disorder)
244Xeroderma Pigmentosum (XP) (著色性乾皮症)
245X-linked Agammaglobulinemia (XLA) (X-連鎖無丙種球蛋白血症)
246X-linked Hypophosphatemic Rickets (XLH) (性聯遺傳型低磷酸鹽佝僂症)
247X-linked Myotubular Myopathy (XLMTM) (肌小管病變)
248X-linked Retinoschisis (XLRS) (Genetic Disorder)
249X-linked Thrombocytopenia (XLT) (Genetic Disorder)