McLeod syndrome

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McLeod syndrome
Classification and external resources
OMIM314850
DiseasesDB29708
GeneReviews
 
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McLeod syndrome
Classification and external resources
OMIM314850
DiseasesDB29708
GeneReviews

McLeod syndrome (or McLeod phenomenon) is a genetic disorder that may affect the blood, brain, peripheral nerves, muscle and heart. It is caused by a variety of recessively-inherited mutations in the XK gene on the X chromosome. The gene is responsible for producing the Kx protein, a secondary supportive protein for the Kell antigen on the red blood cell surface.

Clinical features[edit]

Patients usually begin to notice symptoms in their 50s and the course is usually slowly progressive. Common features include peripheral neuropathy, cardiomyopathy and hemolytic anemia. Other features include limb chorea, facial tics, other oral movements (lip and tongue biting), seizures, a late-onset dementia and behavioral changes.

Laboratory features[edit]

McLeod syndrome is one of only a few disorders in which acanthocytes may be found on the peripheral blood smear. Blood evaluation may show signs of hemolytic anemia. Elevated creatine kinase can be seen with myopathy in McLeod syndrome.

Radiologic and pathologic features[edit]

MRI shows increased T2 signal in the lateral putamen with caudate atrophy and secondary lateral ventricular dilation. Necropsy shows loss of neurons and gliosis in the caudate and globus pallidus. Similar changes may also be seen in the thalamus, substantia nigra and putamen. The cerebellum and cerebral cortex are generally spared.

History[edit]

McLeod syndrome was discovered in 1961 and, as with the Kell antigen system, was named after the first patient in which it was found: a Harvard dental student Hugh McLeod, whose red blood cells were observed to have weak expression of Kell system antigens during blood donation,[1] and his red cells were found to be acanthocytic (spiky) under the microscope.

Genetics[edit]

The McLeod phenotype is a recessive mutation of the Kell blood group system. The McLeod gene encodes the XK protein, which is located on the X chromosome,[2] and has the structural characteristics of a membrane transport protein but an unknown function. Absence of the XK protein is an X-linked disease. [3] Mutational variants result in McLeod syndrome either with or without neuroacanthocytosis: the gene on the X chromosome for McLeod syndrome is physically close to the gene for chronic granulomatous disease. As a result, individuals with one relatively small deletion may have both diseases. [4]

The phenotype may be present without the syndrome presenting.[5]

Epidemiology and disease associations[edit]

McLeod syndrome is present in 0.5 to 1 per 100,000 the population. McLeod males have variable acanthocytosis due to a defect in the inner leaflet bilayer of the red blood cell, as well as mild hemolysis. McLeod females have only occasional acanthocytes and very mild hemolysis; the lesser severity is thought to be due to X chromosome inactivation via the Lyon effect. Some individuals with McLeod phenotype develop myopathy, neuropathy or psychiatric symptoms, producing a syndrome that may mimic chorea.[6][7]

McLeod syndrome can cause an increase in the enzymes creatine kinase (CK) and lactate dehydrogenase (LDH) found in routine blood screening. [8] [9]

Treatment[edit]

There is no cure for McLeod syndrome; the treatment is supportive depending on symptoms. Medication may assist management of epilepsy, cardiac and psychiatric features, although patients may respond poorly to treatment for chorea.

External links[edit]

References[edit]

  1. ^ Allen FH, Krabbe SM, Corcoran PA (September 1961). "A new phenotype (McLeod) in the Kell blood-group system". Vox Sang. 6: 555–60. doi:10.1111/j.1423-0410.1961.tb03203.x. PMID 13860532. 
  2. ^ Arnaud L, Salachas F, Lucien N, et al. (March 2009). "Identification and characterization of a novel XK splice site mutation in a patient with McLeod syndrome". Transfusion 49 (3): 479–84. doi:10.1111/j.1537-2995.2008.02003.x. PMID 19040496. 
  3. ^ Ho MF, Monaco AP, Blonden LA, et al. (February 1992). "Fine mapping of the McLeod locus (XK) to a 150-380-kb region in Xp21". Am. J. Hum. Genet. 50 (2): 317–30. PMC 1682457. PMID 1734714. 
  4. ^ Marsh WL, Oyen R, Nichols ME, Allen FH (February 1975). "Chronic granulomatous disease and the Kell blood groups". Br. J. Haematol. 29 (2): 247–62. PMID 1191546. 
  5. ^ Walker RH, Danek A, Uttner I, Offner R, Reid M, Lee S (February 2007). "McLeod phenotype without the McLeod syndrome". Transfusion 47 (2): 299–305. doi:10.1111/j.1537-2995.2007.01106.x. PMID 17302777. 
  6. ^ Danek A, Rubio JP, Rampoldi L, et al. (December 2001). "McLeod neuroacanthocytosis: genotype and phenotype". Ann. Neurol. 50 (6): 755–64. PMID 11761473. 
  7. ^ Malandrini A, Fabrizi GM, Truschi F, et al. (June 1994). "Atypical McLeod syndrome manifested as X-linked chorea-acanthocytosis, neuromyopathy and dilated cardiomyopathy: report of a family". J. Neurol. Sci. 124 (1): 89–94. doi:10.1016/0022-510X(94)90016-7. PMID 7931427. 
  8. ^ Oechsner M, G. Winkler G, A. Danek A, McLeod neuroacanthocytosis: An underdiagnosed syndrome? International communication forum in human molecular genetics September 6, 1995
  9. ^ Neuromuscular Disease Center Dilated cardiomyopathies ± Myopathy