The McLeod syndrome is a rare X-linked recessive disorder characterized by blood 
group, neuromuscular and haematopoietic abnormalities. It is caused by XK gene 
defects and may include large deletions in the Xp21 region. Analysis of three 
unrelated McLeod patients for the presence of the XK, DMD, CYBB, ETX1, RPGR and 
OTC loci, as well as for the DXS709 marker, revealed deletions from the 39th 
exon of DMD to the ETX1 locus (patient Be), from the XK to RPGR loci (patient 
Bi) and from the XK to CYBB loci (patient Lh). All three patients normally 
expressed the Lutheran (Lu) red cell antigens, thus excluding the interval 
between the RPGR and DMD genes as site of the XS locus, previously mapped to the 
Xp21.2-Xq21.1 region and thought to regulate the expression of the LU blood 
group gene on chromosome 19.