LAUSR

The Kx antigen is the product of the XK gene on the X chromosome and the only known antigen in the XK blood group system. The Kx and Kell proteins are covalently linked on the red blood cells (RBC) membrane, and changes in the XK gene that abolish expression of Kx antigen are associated with very weak expression of Kell system antigens, known as the McLeod phenotype, found almost exclusively in males. The phenotype may be fortuitously detected when screening healthy blood donors. Importantly, XK null and missense mutations can cause the McLeod syndrome which is associated with acanthocytes, a late onset of neurological impairment, chorea-like disease, cardiomyopathy, and various degrees of muscular atrophy. Large deletions in the X chromosome can also cause McLeod syndrome, X-linked Chronic Granulomatous Disorder, and the contiguous gene deletion syndrome. Here, we report the molecular basis of the McLeod phenotype in a healthy male blood donor found by random screening for depressed Kell expression, a patient referred for a family history of a McLeod phenotype, and a patient referred for testing as part of a neurological workup.