Infantile Neuroaxonal Dystrophy

Version	Summary	Created by	Modification	Content Size	Created at	Operation
1		Camila Xu	+ 662 word(s)	662	2020-12-15 07:27:55

This entry is adapted from the peer-reviewed paper https://medlineplus.gov/genetics/condition/infantile-neuroaxonal-dystrophy

Infantile neuroaxonal dystrophy is a disorder that primarily affects the nervous system.

genetic conditions

1. Introduction

Individuals with infantile neuroaxonal dystrophy typically do not have any symptoms at birth, but between the ages of about 6 and 18 months they begin to experience delays in acquiring new motor and intellectual skills, such as crawling or beginning to speak. Eventually they lose previously acquired skills (developmental regression). In some cases, signs and symptoms of infantile neuroaxonal dystrophy first appear later in childhood or during the teenage years and progress more slowly.

Children with infantile neuroaxonal dystrophy experience progressive difficulties with movement. They generally have muscles that are at first weak and "floppy" (hypotonic), and then gradually become very stiff (spastic). Eventually, affected children lose the ability to move independently. Lack of muscle strength causes difficulty with feeding. Muscle weakness can also result in breathing problems that can lead to frequent infections, such as pneumonia. Seizures occur in some affected children.

Rapid, involuntary eye movements (nystagmus), eyes that do not look in the same direction (strabismus), and vision loss due to deterioration (atrophy) of the nerve that carries information from the eye to the brain (the optic nerve) often occur in infantile neuroaxonal dystrophy. Hearing loss may also develop. Children with this disorder experience progressive deterioration of cognitive functions (dementia), and they eventually lose awareness of their surroundings.

Infantile neuroaxonal dystrophy is characterized by the development of swellings called spheroid bodies in the axons, the fibers that extend from nerve cells (neurons) and transmit impulses to muscles and other neurons. In some individuals with infantile neuroaxonal dystrophy, abnormal amounts of iron accumulate in a specific region of the brain called the basal ganglia. The relationship of these features to the symptoms of infantile neuroaxonal dystrophy is unknown.

2. Frequency

Infantile neuroaxonal dystrophy is a very rare disorder. Its specific incidence is unknown.

3. Causes

Mutations in the PLA2G6 gene have been identified in most individuals with infantile neuroaxonal dystrophy. The PLA2G6 gene provides instructions for making a type of enzyme called an A2 phospholipase. This type of enzyme is involved in breaking down (metabolizing) fats called phospholipids. Phospholipid metabolism is important for many body processes, including helping to keep the cell membrane intact and functioning properly. Specifically, the A2 phospholipase produced from the PLA2G6 gene, sometimes called PLA2 group VI, helps to regulate the levels of a compound called phosphatidylcholine, which is abundant in the cell membrane.

Mutations in the PLA2G6 gene impair the function of the PLA2 group VI enzyme, which may disrupt cell membrane maintenance and contribute to the development of spheroid bodies in the nerve axons. Although it is unknown how changes in this enzyme's function lead to the signs and symptoms of infantile neuroaxonal dystrophy, phospholipid metabolism problems have been seen in both this disorder and a similar disorder called pantothenate kinase-associated neurodegeneration. These disorders, as well as the more common Alzheimer disease and Parkinson disease, also are associated with changes in brain iron metabolism. Researchers are studying the links between phospholipid defects, brain iron, and damage to nerve cells, but have not determined how the iron accumulation that occurs in some individuals with infantile neuroaxonal dystrophy may contribute to the features of this disorder.

A few individuals with infantile neuroaxonal dystrophy have not been found to have mutations in the PLA2G6 gene. The genetic cause of the condition in these cases is unknown; there is evidence that at least one other unidentified gene may be involved.

4. Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

5. Other Names for This Condition

INAD
NBIA, PLA2G6-related
neurodegeneration with brain iron accumulation, PLA2G6-related
Seitelberger disease
Seitelberger's disease

References

Engel LA, Jing Z, O'Brien DE, Sun M, Kotzbauer PT. Catalytic function ofPLA2G6 is impaired by mutations associated with infantile neuroaxonal dystrophybut not dystonia-parkinsonism. PLoS One. 2010 Sep 23;5(9):e12897. doi:10.1371/journal.pone.0012897.
Hayflick SJ. Neurodegeneration with brain iron accumulation: from genes topathogenesis. Semin Pediatr Neurol. 2006 Sep;13(3):182-5. Review.
Khateeb S, Flusser H, Ofir R, Shelef I, Narkis G, Vardi G, Shorer Z, Levy R,Galil A, Elbedour K, Birk OS. PLA2G6 mutation underlies infantile neuroaxonaldystrophy. Am J Hum Genet. 2006 Nov;79(5):942-8.
Kurian MA, Morgan NV, MacPherson L, Foster K, Peake D, Gupta R, Philip SG,Hendriksz C, Morton JE, Kingston HM, Rosser EM, Wassmer E, Gissen P, Maher ER.Phenotypic spectrum of neurodegeneration associated with mutations in the PLA2G6 gene (PLAN). Neurology. 2008 Apr 29;70(18):1623-9. doi:10.1212/01.wnl.0000310986.48286.8e.
McNeill A, Chinnery PF. Neurodegeneration with brain iron accumulation. Handb Clin Neurol. 2011;100:161-72. doi: 10.1016/B978-0-444-52014-2.00009-4. Review.
Morgan NV, Westaway SK, Morton JE, Gregory A, Gissen P, Sonek S, Cangul H,Coryell J, Canham N, Nardocci N, Zorzi G, Pasha S, Rodriguez D, Desguerre I,Mubaidin A, Bertini E, Trembath RC, Simonati A, Schanen C, Johnson CA, LevinsonB, Woods CG, Wilmot B, Kramer P, Gitschier J, Maher ER, Hayflick SJ. PLA2G6,encoding a phospholipase A2, is mutated in neurodegenerative disorders with high brain iron. Nat Genet. 2006 Jul;38(7):752-4.Genet. 2006 Aug;38(8):957.
Polster B, Crosier M, Lindsay S, Hayflick S. Expression of PLA2G6 in humanfetal development: Implications for infantile neuroaxonal dystrophy. Brain ResBull. 2010 Nov 20;83(6):374-9. doi: 10.1016/j.brainresbull.2010.08.011.
Schneider SA, Hardy J, Bhatia KP. Syndromes of neurodegeneration with brainiron accumulation (NBIA): an update on clinical presentations, histological andgenetic underpinnings, and treatment considerations. Mov Disord. 2012Jan;27(1):42-53. doi: 10.1002/mds.23971.
Wu Y, Jiang Y, Gao Z, Wang J, Yuan Y, Xiong H, Chang X, Bao X, Zhang Y, XiaoJ, Wu X. Clinical study and PLA2G6 mutation screening analysis in Chinesepatients with infantile neuroaxonal dystrophy. Eur J Neurol. 2009Feb;16(2):240-5. doi: 10.1111/j.1468-1331.2008.02397.x.

©Text is available under the terms and conditions of the Creative Commons-Attribution ShareAlike (CC BY-SA) license; additional terms may apply. By using this site, you agree to the Terms and Conditions and Privacy Policy.

Upload a video for this entry

Information

Subjects: Genetics & Heredity

Contributor MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register :

Camila Xu

View Times: 410

Entry Collection: MedlinePlus

Update Date: 23 Dec 2020

Table of Contents

Video Upload Options

Confirm

1. Introduction

2. Frequency

3. Causes

4. Inheritance

5. Other Names for This Condition

References

Video Upload Options

Confirm

1. Introduction

2. Frequency

3. Causes

3.1. The gene associated with Infantile neuroaxonal dystrophy

4. Inheritance

5. Other Names for This Condition

References