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Hypomyelinating leukodystrophy 2(PMLD1; HLD2)

MedGen UID:
325157
Concept ID:
C1837355
Disease or Syndrome
Synonym: PELIZAEUS-MERZBACHER-LIKE DISEASE, 1
SNOMED CT: Pelizaeus Merzbacher like disease due to GJC2 mutation (870287007)
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
Intellectual Product
Source: Orphanet
A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele).
 
Gene (location): GJC2 (1q42.13)
 
Monarch Initiative: MONDO:0012125
OMIM®: 608804
Orphanet: ORPHA280282

Disease characteristics

Excerpted from the GeneReview: Pelizaeus-Merzbacher-Like Disease 1
Pelizaeus-Merzbacher-like disease 1 (PMLD1) is a slowly progressive leukodystrophy that typically presents during the neonatal or early-infantile period with nystagmus, commonly associated with hypotonia, delayed acquisition of motor milestones, speech delay, and dysarthria. Over time the hypotonia typically evolves into spasticity that affects the ability to walk and communicate. Cerebellar signs (gait ataxia, dysmetria, intention tremor, head titubation, and dysdiadochokinesia) frequently manifest during childhood. Some individuals develop extrapyramidal movement abnormalities (choreoathetosis and dystonia). Hearing loss and optic atrophy are observed in rare cases. Motor impairments can lead to swallowing difficulty and orthopedic complications, including hip dislocation and scoliosis. Most individuals have normal cognitive skills or mild intellectual disability – which, however, can be difficult to evaluate in the context of profound motor impairment. [from GeneReviews]
Authors:
Norah Nahhas  |  Alex Conant  |  Jennifer Orthmann-Murphy, et. al.   view full author information

Additional description

From MedlinePlus Genetics
Pelizaeus-Merzbacher-like disease type 1 is an inherited condition involving the brain and spinal cord (central nervous system). This disease is one of a group of genetic disorders called leukodystrophies. Leukodystrophies are abnormalities of the nervous system's white matter, which consists of nerve fibers covered by a fatty substance called myelin. Myelin insulates nerve fibers and promotes the rapid transmission of nerve impulses. In particular, Pelizaeus-Merzbacher-like disease type 1 involves hypomyelination, which means that the nervous system has a reduced ability to form myelin. The signs and symptoms of this condition are very similar to another leukodystrophy called Pelizaeus-Merzbacher disease, but the two disorders have different genetic causes.

Beginning in the first few months of life, infants with Pelizaeus-Merzbacher-like disease type 1 typically experience weak muscle tone (hypotonia), involuntary movements of the eyes (nystagmus), and delayed development of speech and motor skills, such as sitting or grasping objects. As children with Pelizaeus-Merzbacher-like disease type 1 get older, hypotonia changes to muscle stiffness (spasticity).

During childhood, individuals with Pelizaeus-Merzbacher-like disease type 1 develop problems with movement and balance (ataxia), difficulty with movements that involve judging distance or scale (dysmetria), tremors that occur mainly during movement (intention tremors), and head and neck tremors (titubation). People with this condition have an inability to perform quick, alternating movements (dysdiadochokinesia), such as quickly tapping different fingers. Some develop involuntary tensing of the muscles (dystonia) and jerking (choreiform) movements. Many people with Pelizaeus-Merzbacher-like disease type 1 develop skeletal issues such as an abnormal curvature of the spine (scoliosis) and require wheelchair assistance from childhood.

Muscle abnormalities can lead to difficulty swallowing and problems producing speech (expressive language), but affected individuals can understand speech (receptive language). Most individuals with Pelizaeus-Merzbacher-like disease type 1 have normal intelligence. Rarely, hearing loss, optic atrophy, and recurrent seizures (epilepsy) can occur.  https://medlineplus.gov/genetics/condition/pelizaeus-merzbacher-like-disease-type-1

Clinical features

From HPO
Cerebellar ataxia
MedGen UID:
849
Concept ID:
C0007758
Disease or Syndrome
Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).
Dysarthria
MedGen UID:
8510
Concept ID:
C0013362
Mental or Behavioral Dysfunction
Dysarthric speech is a general description referring to a neurological speech disorder characterized by poor articulation. Depending on the involved neurological structures, dysarthria may be further classified as spastic, flaccid, ataxic, hyperkinetic and hypokinetic, or mixed.
Dystonic disorder
MedGen UID:
3940
Concept ID:
C0013421
Sign or Symptom
An abnormally increased muscular tone that causes fixed abnormal postures. There is a slow, intermittent twisting motion that leads to exaggerated turning and posture of the extremities and trunk.
Leukodystrophy
MedGen UID:
6070
Concept ID:
C0023520
Disease or Syndrome
Leukodystrophy refers to deterioration of white matter of the brain resulting from degeneration of myelin sheaths in the CNS. Their basic defect is directly related to the synthesis and maintenance of myelin membranes. Symmetric white matter involvement at MRI is a typical finding in patients with leukodystrophies.
Babinski sign
MedGen UID:
19708
Concept ID:
C0034935
Finding
Upturning of the big toe (and sometimes fanning of the other toes) in response to stimulation of the sole of the foot. If the Babinski sign is present it can indicate damage to the corticospinal tract.
Seizure
MedGen UID:
20693
Concept ID:
C0036572
Sign or Symptom
A seizure is an intermittent abnormality of nervous system physiology characterised by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.
Spastic paraparesis
MedGen UID:
52432
Concept ID:
C0037771
Sign or Symptom
Mild or moderate loss of motor function accompanied by spasticity in the lower extremities. This condition is a manifestation of CENTRAL NERVOUS SYSTEM DISEASES that cause injury to the motor cortex or descending motor pathways.
Choreoathetosis
MedGen UID:
39313
Concept ID:
C0085583
Disease or Syndrome
Involuntary movements characterized by both athetosis (inability to sustain muscles in a fixed position) and chorea (widespread jerky arrhythmic movements).
Focal aware seizure
MedGen UID:
65895
Concept ID:
C0234974
Disease or Syndrome
A type of focal-onset seizure in which awareness is preserved. Awareness during a seizure is defined as the patient being fully aware of themself and their environment throughout the seizure, even if immobile.
Cerebral atrophy
MedGen UID:
116012
Concept ID:
C0235946
Disease or Syndrome
Atrophy (wasting, decrease in size of cells or tissue) affecting the cerebrum.
Focal impaired awareness seizure
MedGen UID:
543022
Concept ID:
C0270834
Disease or Syndrome
Focal impaired awareness seizure (or focal seizure with impaired or lost awareness) is a type of focal-onset seizure characterized by some degree (which may be partial) of impairment of the person's awareness of themselves or their surroundings at any point during the seizure.
Cognitive impairment
MedGen UID:
90932
Concept ID:
C0338656
Mental or Behavioral Dysfunction
Abnormal cognition is characterized by deficits in thinking, reasoning, or remembering.
Global developmental delay
MedGen UID:
107838
Concept ID:
C0557874
Finding
A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.
Head titubation
MedGen UID:
299071
Concept ID:
C1608410
Sign or Symptom
A head tremor of moderate speed (3 to 4 Hz) in the anterior-posterior direction.
Sensory axonal neuropathy
MedGen UID:
334116
Concept ID:
C1842587
Finding
An axonal neuropathy of peripheral sensory nerves.
Poor speech
MedGen UID:
341172
Concept ID:
C1848207
Finding
Motor delay
MedGen UID:
381392
Concept ID:
C1854301
Finding
A type of Developmental delay characterized by a delay in acquiring motor skills.
Decreased motor nerve conduction velocity
MedGen UID:
388130
Concept ID:
C1858729
Finding
A type of decreased nerve conduction velocity that affects the motor neuron.
Progressive spasticity
MedGen UID:
347171
Concept ID:
C1859520
Finding
Spasticity that increases in degree with time.
Demyelinating motor neuropathy
MedGen UID:
409836
Concept ID:
C1969462
Finding
Demyelination of peripheral motor nerves.
Cerebral hypomyelination
MedGen UID:
383084
Concept ID:
C2677328
Finding
Reduced amount of myelin in the nervous system resulting from defective myelinogenesis in the white matter of the central nervous system.
Intention tremor
MedGen UID:
1642960
Concept ID:
C4551520
Sign or Symptom
A type of kinetic tremor that occurs during target directed movement is called intention tremor. That is, an oscillatory cerebellar ataxia that tends to be absent when the limbs are inactive and during the first part of voluntary movement but worsening as the movement continues and greater precision is required (e.g., in touching a target such as the patient's nose or a physician's finger).
Rigidity
MedGen UID:
7752
Concept ID:
C0026837
Sign or Symptom
Continuous involuntary sustained muscle contraction. When an affected muscle is passively stretched, the degree of resistance remains constant regardless of the rate at which the muscle is stretched. This feature helps to distinguish rigidity from muscle spasticity.
Facial palsy
MedGen UID:
87660
Concept ID:
C0376175
Disease or Syndrome
Facial nerve palsy is a dysfunction of cranial nerve VII (the facial nerve) that results in inability to control facial muscles on the affected side with weakness of the muscles of facial expression and eye closure. This can either be present in unilateral or bilateral form.
Poor head control
MedGen UID:
322809
Concept ID:
C1836038
Finding
Difficulty to maintain correct position of the head while standing or sitting.
Axial hypotonia
MedGen UID:
342959
Concept ID:
C1853743
Finding
Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk.
Myopia
MedGen UID:
44558
Concept ID:
C0027092
Disease or Syndrome
Nearsightedness, also known as myopia, is an eye condition that causes blurry distance vision. People who are nearsighted have more trouble seeing things that are far away (such as when driving) than things that are close up (such as when reading or using a computer). If it is not treated with corrective lenses or surgery, nearsightedness can lead to squinting, eyestrain, headaches, and significant visual impairment.\n\nNearsightedness usually begins in childhood or adolescence. It tends to worsen with age until adulthood, when it may stop getting worse (stabilize). In some people, nearsightedness improves in later adulthood.\n\nFor normal vision, light passes through the clear cornea at the front of the eye and is focused by the lens onto the surface of the retina, which is the lining of the back of the eye that contains light-sensing cells. People who are nearsighted typically have eyeballs that are too long from front to back. As a result, light entering the eye is focused too far forward, in front of the retina instead of on its surface. It is this change that causes distant objects to appear blurry. The longer the eyeball is, the farther forward light rays will be focused and the more severely nearsighted a person will be.\n\nNearsightedness is measured by how powerful a lens must be to correct it. The standard unit of lens power is called a diopter. Negative (minus) powered lenses are used to correct nearsightedness. The more severe a person's nearsightedness, the larger the number of diopters required for correction. In an individual with nearsightedness, one eye may be more nearsighted than the other.\n\nEye doctors often refer to nearsightedness less than -5 or -6 diopters as "common myopia." Nearsightedness of -6 diopters or more is commonly called "high myopia." This distinction is important because high myopia increases a person's risk of developing other eye problems that can lead to permanent vision loss or blindness. These problems include tearing and detachment of the retina, clouding of the lens (cataract), and an eye disease called glaucoma that is usually related to increased pressure within the eye. The risk of these other eye problems increases with the severity of the nearsightedness. The term "pathological myopia" is used to describe cases in which high myopia leads to tissue damage within the eye.
Nystagmus
MedGen UID:
45166
Concept ID:
C0028738
Disease or Syndrome
Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.
Optic atrophy
MedGen UID:
18180
Concept ID:
C0029124
Disease or Syndrome
Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy.
Rotary nystagmus
MedGen UID:
116106
Concept ID:
C0240595
Disease or Syndrome
A form of nystagmus in which the eyeball makes rotary motions around the axis.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
  • CROGVHypomyelinating leukodystrophy 2
Follow this link to review classifications for Hypomyelinating leukodystrophy 2 in Orphanet.

Professional guidelines

PubMed

Anheim M, Torres Martin JV, Kolb SA
Cerebellum 2020 Apr;19(2):243-251. doi: 10.1007/s12311-020-01102-0. PMID: 31933160
Osorio MJ, Rowitch DH, Tesar P, Wernig M, Windrem MS, Goldman SA
Stem Cells 2017 Feb;35(2):311-315. Epub 2016 Nov 23 doi: 10.1002/stem.2530. PMID: 27882623Free PMC Article

Recent clinical studies

Etiology

Georgiou E, Sidiropoulou K, Richter J, Papaneophytou C, Sargiannidou I, Kagiava A, von Jonquieres G, Christodoulou C, Klugmann M, Kleopa KA
Brain 2017 Mar 1;140(3):599-616. doi: 10.1093/brain/aww351. PMID: 28100454Free PMC Article

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