About Hallervorden-Spatz Syndrome And Its Underlying Genetic Causes

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What Is Hallervorden-Spatz Syndrome?

Hallervorden-Spatz syndrome (HSS), or Hallervorden-Spatz disease, is an autosomal recessive genetic disorder that causes movement defects, among other troubling symptoms, in those who suffer from it. Specifically, HSS causes neurodegeneration, or neuron death, and an excessive iron accumulation. These problems lead to one or more of the following symptoms that usually arise shortly after birth, but can also arise in later childhood:

Involuntary muscle contractions (otherwise known as dystonia)
Movement defects, such as uncontrollable twisting and squirming
Weak muscles
Tight or spastic muscles
Dementia
Seizures
Tremor (continuous shaking, especially of the hands)
Vision problems
Speech problems

Due to the number and magnitude of HSS’s symptoms, treatment options are limited. In some cases, vitamins, especially ones that contain antioxidants like Coenzyme Q10 and pantothenate, help ease symptom severity. Most individuals who are inflicted with HSS typically die early in life and, in the worst cases, soon after their symptoms manifest.

What Is Known Abot The Genetics Of Hallervorden-Spatz Syndrome?

Molecular geneticists initially determined that mutations that cause HSS are located on human chromosome 20. They later identifed a single gene designated PANK2 that, when mutated, is causative of HSS. PANK2 encodes a pantothenate kinase protein which functions in mitochondria, which are the components of a cell that are responsible for generating energy. This pantothenate kinase protein is required for the proper production a second protein known as coenzyme A. Coenzyme A is ubiquitous to all cells in our bodies and helps carry out the essential task of converting fats, sugars, and certain amino acids into energy.

People who have mutations in both copies of their PANK2 gene produce defective pantothenate kinase protein, and therefore have difficulty in generating a sufficient amount of coenyzme A to produce needed energy. The inefficiency of their pantothenate kinase protein, and therefore the severity of their symptoms, is dependent on the nature of the mutations to their PANK2 genes. If the effects of the mutations is so severe that pantothenate kinase protein is not even made, the affected individual is likely to have severe symptoms. Conversely, if the mutations are missense mutations that cause single amino acid changes to a protein, particularly ones that affect non-critical portions of the pantothenate kinase protein, the affected individual’s symptoms are likely to be relatively mild.

It has been determined, however, that there are a reduced number of HSS patients who do not have mutations in PANK2, which suggests that mutations in one or more other genes may causative of HSS. While this gene (or genes) remains unknown, molecular biologists are working to determine whether another gene is, in fact, involved. It is hoped that a very comprehensive knowledge of HSS and all of its genetic causes will lead to the development of an effective treatment course that is currently lacking.

References

Genetics Home Reference, National institutes of Health, PANK2: https://ghr.nlm.nih.gov/gene/PANK2

Medline Plus, National Institutes of Health, Hallervorden-Spatz disease: https://www.nlm.nih.gov/medlineplus/ency/article/001225.htm

S.J. Hayflick et al., Genetic, Clinical, and Radiographic Delineation of Hallervorden-Spatz Syndrome: New England Journal of Medicine, 348:33-40 (2003). https://www.nejm.org/doi/full/10.1056/NEJMoa020817