McLeod Syndrome (MLS) is a rare X-linked disorder characterized by haemopoietic 
abnormalities and late-onset neurological and muscular defects. The McLeod blood 
group phenotype is typically associated with erythrocyte acanthocytosis, absence 
of the Kx antigen and reduced expression of Kell system antigens. MLS is caused 
by hemizygosity for mutations in the XK gene. We describe a patient with MLS who 
first showed symptoms in 1989 (aged 51 years). As the disease progressed, the 
patient developed a slight dementia, aggressive behaviour and choreatic 
movements. A cardiomyopathy was also diagnosed. An electroneuromyography showed 
neuropathic and myopathic changes. Liver enzymes were elevated and a blood smear 
showed acanthocytes. MLS was confirmed by serological analysis of the Kell 
antigens. Analysis of red blood cells by flow cytometry revealed the patient and 
his grandson to have reduced Kell antigen expression. The patient's daughters 
had two populations of red cells, consistent with them being heterozygous for an 
XK0 allele. The molecular basis of MLS in this family is a novel mutation 
consisting of a 7453-bp deletion that includes exon 2 of the XK gene. This 
confirms that the patient's 7-year-old grandson, who is currently asymptomatic, 
also has the XK0 allele and is therefore likely to develop MLS.