BACKGROUND: McLeod neuroacanthocytosis syndrome is a late-onset X-linked 
multisystem disorder affecting the peripheral and central nervous systems, red 
blood cells (RBCs), and internal organs. A variety of mutations have been found 
in the responsible gene (XK) including single nonsense and missense mutations, 
nucleotide mutations at or near the splice junctions of introns of XK, and 
different deletion mutations. To date no clear phenotype-genotype correlation is 
apparent. The clinical details of one case of McLeod phenotype without apparent 
neuromuscular abnormalities have been reported. Here the clinical details of two 
additional cases are presented, of which the genetic details have previously 
been published.
STUDY DESIGN AND METHODS: Two asymptomatic or minimally symptomatic cases at 
ages expected to manifest the McLeod syndrome (MLS) were evaluated. The first 
case had been authenticated as a genuine McLeod both by serology and by 
genotyping (R222G missense mutation) and the second case had a mutation in XK 
(IVS2+5G>A) and by serology exhibited very weak Kx antigen and no detectable 
Kell antigens, except extremely low k antigen by adsorption-elution technique. 
The patients were examined for hematologic, neurologic, and other clinical 
abnormalities.
RESULTS: Despite documented McLeod phenotype on RBCs, and identified mutations 
of XK, neurologic and other clinical findings were minimal at ages expected to 
manifest MLS.
CONCLUSIONS: The different XK mutations may have different effects upon the XK 
gene product and thus may account for the variable phenotype.