What is the pathophysiology of Chédiak-Higashi syndrome (CHS)?

Updated: Aug 08, 2019
  • Author: Roman J Nowicki, MD, PhD; Chief Editor: Dirk M Elston, MD  more...
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Answer

Chédiak-Higashi syndrome (CHS) is an autosomal recessive immunodeficiency disorder characterized by abnormal intracellular protein transport. The Chédiak-Higashi syndrome gene was characterized in 1996 as the LYST or CHS1 gene and is localized to bands 1q42-43. The CHS protein is expressed in the cytoplasm of cells of a variety of tissues and may represent an abnormality of organellar protein trafficking. [6]

The CHS gene affects the synthesis and/or maintenance of storage/secretory granules in various types of cells. Lysosomes of leukocytes and fibroblasts, dense bodies of platelets, azurophilic granules of neutrophils, and melanosomes of melanocytes are generally larger in size and irregular in morphology, indicating that a common pathway in the synthesis of organelles responsible for storage is affected in patients with CHS. [7] In the early stages of neutrophil maturation, normal azurophil granules fuse to form megagranules, whereas, in the later stage (ie, during myelocyte stage), normal granules are formed. The mature neutrophils contain both populations. A similar phenomenon occurs in monocytes. The impaired function in the polymorphonuclear leukocytes may be related to abnormal microtubular assembly.

The disease is often fatal in childhood as a result of infection or an accelerated lymphomalike phase; therefore, few patients live to adulthood. In these patients, a progressive neurologic dysfunction may be the dominant feature. Neurologic involvement is variable but often includes peripheral neuropathy. The mechanism of peripheral neuropathy in CHS has not been completely elucidated. Both the axonal type and the demyelinating type of peripheral neuropathy associated with CHS have been reported.

Defective melanization of melanosomes occurs in oculocutaneous albinism associated with CHS. In melanocytes, autophagocytosis of melanosomes occurs.

Most patients also undergo an accelerated phase or accelerated reaction, which is a nonmalignant lymphohistiocytic lymphomalike infiltration of multiple organs that occurs in more than 80% of patients. This lymphomalike stage is precipitated by viruses, particularly by infection by the Epstein-Barr virus. It is associated with anemia, bleeding episodes, and overwhelming infections leading to death. Infections most commonly involve the skin, the lungs, and the respiratory tract and are usually due to Staphylococcus aureus, Streptococcus pyogenes, and Pneumococcus species.


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