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Leukoencephalopathy, ataxia, hypodontia, hypomyelination syndrome(HLD7)

MedGen UID:
1639554
Concept ID:
C4706676
Disease or Syndrome
Synonyms: ATAXIA, DELAYED DENTITION, AND HYPOMYELINATION; HLD7; Hypomyelinating leukodystrophy-ataxia-hypodontia-hypomyelination syndrome; Leukodystrophy with oligodontia; LEUKODYSTROPHY, HYPOMYELINATING, 7, WITH OLIGODONTIA; LEUKODYSTROPHY, HYPOMYELINATING, 7, WITH OLIGODONTIA AND HYPOGONADOTROPIC HYPOGONADISM; LEUKODYSTROPHY, HYPOMYELINATING, 7, WITH OR WITHOUT OLIGODONTIA AND/OR HYPOGONADOTROPIC HYPOGONADISM; LEUKODYSTROPHY, HYPOMYELINATING, 7, WITHOUT OLIGODONTIA OR HYPOGONADOTROPIC HYPOGONADISM; Leukodystrophy, hypomyelinating, with hypodontia and hypogonadotropic hypogonadism; LEUKOENCEPHALOPATHY, HYPOMYELINATING, WITH ATAXIA AND DELAYED DENTITION
SNOMED CT: Ataxia, delayed dentition, hypomyelination syndrome (764095005); Leukoencephalopathy, ataxia, hypodontia, hypomyelination syndrome (764095005)
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).
 
Genes (locations): POLR3A (10q22.3); POLR3B (12q23.3)
 
Monarch Initiative: MONDO:0011897
OMIM®: 607694
Orphanet: ORPHA137639

Authors:

Additional description

From OMIM
Hypomyelinating leukodystrophy-7 (HLD7) is an autosomal recessive neurodegenerative disorder characterized by childhood onset of progressive motor decline manifest as spasticity, ataxia, tremor, and cerebellar signs, as well as mild cognitive regression. Other features may include hypodontia or oligodontia and hypogonadotropic hypogonadism. There is considerable inter- and intrafamilial variability (summary by Bernard et al., 2011). See also HLD8 (614381), which has similar features and is caused by mutation in the POLR3B gene (614366) on chromosome 12q23. The POLR3A and POLR3B genes encode the 2 largest subunits of RNA polymerase III. For a general phenotypic description and a discussion of genetic heterogeneity of hypomyelinating leukodystrophy, see 312080.  http://www.omim.org/entry/607694

Clinical features

From HPO
Short stature
MedGen UID:
87607
Concept ID:
C0349588
Finding
A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms).
Dysphagia
MedGen UID:
41440
Concept ID:
C0011168
Disease or Syndrome
Difficulty in swallowing.
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.
Spasticity
MedGen UID:
7753
Concept ID:
C0026838
Sign or Symptom
A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes.
Peripheral neuropathy
MedGen UID:
18386
Concept ID:
C0031117
Disease or Syndrome
Peripheral neuropathy is a general term for any disorder of the peripheral nervous system. The main clinical features used to classify peripheral neuropathy are distribution, type (mainly demyelinating versus mainly axonal), duration, and course.
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 characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.
Tremor
MedGen UID:
21635
Concept ID:
C0040822
Sign or Symptom
An unintentional, oscillating to-and-fro muscle movement about a joint axis.
Hyperreflexia
MedGen UID:
57738
Concept ID:
C0151889
Finding
Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles.
Dysmetria
MedGen UID:
68583
Concept ID:
C0234162
Finding
A type of ataxia characterized by the inability to carry out movements with the correct range and motion across the plane of more than one joint related to incorrect estimation of the distances required for targeted movements.
Postural tremor
MedGen UID:
66696
Concept ID:
C0234378
Sign or Symptom
A type of tremors that is triggered by holding a limb in a fixed position.
Hypoplasia of the corpus callosum
MedGen UID:
138005
Concept ID:
C0344482
Congenital Abnormality
Underdevelopment of the corpus callosum.
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.
Cerebellar atrophy
MedGen UID:
196624
Concept ID:
C0740279
Disease or Syndrome
Cerebellar atrophy is defined as a cerebellum with initially normal structures, in a posterior fossa with normal size, which displays enlarged fissures (interfolial spaces) in comparison to the foliae secondary to loss of tissue. Cerebellar atrophy implies irreversible loss of tissue and result from an ongoing progressive disease until a final stage is reached or a single injury, e.g. an intoxication or infectious event.
Developmental regression
MedGen UID:
324613
Concept ID:
C1836830
Disease or Syndrome
Loss of developmental skills, as manifested by loss of developmental milestones.
Loss of ambulation
MedGen UID:
332305
Concept ID:
C1836843
Finding
Inability to walk in a person who previous had the ability to walk.
CNS hypomyelination
MedGen UID:
892446
Concept ID:
C4025616
Finding
Reduced amount of myelin in the central nervous system resulting from defective myelinogenesis.
Cerebral cortical atrophy
MedGen UID:
1646740
Concept ID:
C4551583
Disease or Syndrome
Atrophy of the cortex of the cerebrum.
Drooling
MedGen UID:
8484
Concept ID:
C0013132
Finding
Habitual flow of saliva out of the mouth.
Partial congenital absence of teeth
MedGen UID:
43794
Concept ID:
C0020608
Congenital Abnormality
Tooth agenesis in some form is a common human anomaly that affects approximately 20% of the population. Although tooth agenesis is associated with numerous syndromes, several case reports describe nonsyndromic forms that are either sporadic or familial in nature, as reviewed by Gorlin et al. (1990). The incidence of familial tooth agenesis varies with each class of teeth. Most commonly affected are third molars (wisdom teeth), followed by either upper lateral incisors or lower second premolars; agenesis involving first and second molars is very rare. Also see 114600 and 302400. Selective tooth agenesis without associated systemic disorders has sometimes been divided into 2 types: oligodontia, defined as agenesis of 6 or more permanent teeth, and hypodontia, defined as agenesis of less than 6 teeth. The number in both cases does not include absence of third molars (wisdom teeth). Faulty use of the terms, however, have confounded their use. The term 'partial anodontia' is obsolete (Salinas, 1978). Genetic Heterogeneity of Selective Tooth Agenesis Other forms of selective tooth agenesis include STHAG2 (602639), mapped to chromosome 16q12; STHAG3 (604625), caused by mutation in the PAX9 gene (167416) on chromosome 14q12; STHAG4 (150400), caused by mutation in the WNT10A gene (606268) on chromosome 2q35; STHAG5 (610926), mapped to chromosome 10q11; STHAG7 (616724), caused by mutation in the LRP6 gene (603507) on chromosome 12p13; STHAG8 (617073), caused by mutation in the WNT10B gene (601906) on chromosome 12q13; STHAG9 (617275), caused by mutation in the GREM2 gene (608832) on chromosome 1q43; STHAG10 (620173), caused by mutation in the TSPEAR gene (612920) on chromosome 21q22; and STHAGX1 (313500), caused by mutation in the EDA gene (300451) on chromosome Xq13. A type of selective tooth agenesis that was formerly designated STHAG6 has been incorporated into the dental anomalies and short stature syndrome (DASS; 601216). Of 34 unrelated patients with nonsyndromic tooth agenesis, van den Boogaard et al. (2012) found that 56% (19 patients) had mutations in the WNT10A gene (STHAG4), whereas only 3% and 9% had mutations in the MSX1 (STHAG1) and PAX9 (STHAG3) genes, respectively. The authors concluded that WNT10A is a major gene in the etiology of isolated hypodontia. Genotype-Phenotype Correlations Yu et al. (2016) observed that the most frequently missing permanent teeth in WNT10B-associated oligodontia were the lateral incisors (83.3%), whereas premolars were missing only 51.4% of the time, which they noted was a pattern 'clearly different' from the oligodontia patterns resulting from WNT10A mutations. They also stated that the selective pattern in WNT10B mutants was different from that associated with mutations in other genes, such as MSX1, in which second premolars are missing, and PAX9, in which there is agenesis of molars.
Oligodontia
MedGen UID:
904670
Concept ID:
C4082304
Congenital Abnormality
The absence of six or more teeth from the normal series by a failure to develop.
Delayed puberty
MedGen UID:
46203
Concept ID:
C0034012
Pathologic Function
Passing the age when puberty normally occurs with no physical or hormonal signs of the onset of puberty.
Hypogonadotropic hypogonadism
MedGen UID:
82883
Concept ID:
C0271623
Disease or Syndrome
Hypogonadotropic hypogonadism is characterized by reduced function of the gonads (testes in males or ovaries in females) and results from the absence of the gonadal stimulating pituitary hormones
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.
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.
Abnormality of ocular smooth pursuit
MedGen UID:
322909
Concept ID:
C1836393
Finding
An abnormality of eye movement characterized by impaired smooth-pursuit eye movements.
Vertical supranuclear gaze palsy
MedGen UID:
334385
Concept ID:
C1843369
Disease or Syndrome
A supranuclear gaze palsy is an inability to look in a vertical direction as a result of cerebral impairment. There is a loss of the voluntary aspect of eye movements, but, as the brainstem is still intact, all the reflex conjugate eye movements are normal.
Gaze-evoked nystagmus
MedGen UID:
1808161
Concept ID:
C5574666
Disease or Syndrome
Nystagmus made apparent by looking to the right or to the left.

Recent clinical studies

Etiology

Tewari VV, Mehta R, Sreedhar CM, Tewari K, Mohammad A, Gupta N, Gulati S, Kabra M
BMC Pediatr 2018 Apr 4;18(1):126. doi: 10.1186/s12887-018-1108-9. PMID: 29618326Free PMC Article
Battini R, Bertelloni S, Astrea G, Casarano M, Travaglini L, Baroncelli G, Pasquariello R, Bertini E, Cioni G
BMC Med Genet 2015 Jul 25;16:53. doi: 10.1186/s12881-015-0203-0. PMID: 26204956Free PMC Article
Vanderver A, Tonduti D, Bernard G, Lai J, Rossi C, Carosso G, Quezado M, Wong K, Schiffmann R
J Neuropathol Exp Neurol 2013 Jan;72(1):67-75. doi: 10.1097/NEN.0b013e31827c99d2. PMID: 23242285Free PMC Article
Bernard G, Chouery E, Putorti ML, Tétreault M, Takanohashi A, Carosso G, Clément I, Boespflug-Tanguy O, Rodriguez D, Delague V, Abou Ghoch J, Jalkh N, Dorboz I, Fribourg S, Teichmann M, Megarbane A, Schiffmann R, Vanderver A, Brais B
Am J Hum Genet 2011 Sep 9;89(3):415-23. doi: 10.1016/j.ajhg.2011.07.014. PMID: 21855841Free PMC Article

Diagnosis

Currie AD, Karmarkar SA
Pediatr Neurol 2018 Mar;80:94-95. Epub 2017 Dec 27 doi: 10.1016/j.pediatrneurol.2017.06.013. PMID: 29429779
Battini R, Bertelloni S, Astrea G, Casarano M, Travaglini L, Baroncelli G, Pasquariello R, Bertini E, Cioni G
BMC Med Genet 2015 Jul 25;16:53. doi: 10.1186/s12881-015-0203-0. PMID: 26204956Free PMC Article
Vanderver A, Tonduti D, Bernard G, Lai J, Rossi C, Carosso G, Quezado M, Wong K, Schiffmann R
J Neuropathol Exp Neurol 2013 Jan;72(1):67-75. doi: 10.1097/NEN.0b013e31827c99d2. PMID: 23242285Free PMC Article
Bernard G, Chouery E, Putorti ML, Tétreault M, Takanohashi A, Carosso G, Clément I, Boespflug-Tanguy O, Rodriguez D, Delague V, Abou Ghoch J, Jalkh N, Dorboz I, Fribourg S, Teichmann M, Megarbane A, Schiffmann R, Vanderver A, Brais B
Am J Hum Genet 2011 Sep 9;89(3):415-23. doi: 10.1016/j.ajhg.2011.07.014. PMID: 21855841Free PMC Article
Orcesi S, Tonduti D, Uggetti C, Larizza D, Fazzi E, Balottin U
Pediatr Neurol 2010 May;42(5):359-64. doi: 10.1016/j.pediatrneurol.2010.01.015. PMID: 20399393

Prognosis

Battini R, Bertelloni S, Astrea G, Casarano M, Travaglini L, Baroncelli G, Pasquariello R, Bertini E, Cioni G
BMC Med Genet 2015 Jul 25;16:53. doi: 10.1186/s12881-015-0203-0. PMID: 26204956Free PMC Article
Vanderver A, Tonduti D, Bernard G, Lai J, Rossi C, Carosso G, Quezado M, Wong K, Schiffmann R
J Neuropathol Exp Neurol 2013 Jan;72(1):67-75. doi: 10.1097/NEN.0b013e31827c99d2. PMID: 23242285Free PMC Article
Bernard G, Chouery E, Putorti ML, Tétreault M, Takanohashi A, Carosso G, Clément I, Boespflug-Tanguy O, Rodriguez D, Delague V, Abou Ghoch J, Jalkh N, Dorboz I, Fribourg S, Teichmann M, Megarbane A, Schiffmann R, Vanderver A, Brais B
Am J Hum Genet 2011 Sep 9;89(3):415-23. doi: 10.1016/j.ajhg.2011.07.014. PMID: 21855841Free PMC Article

Clinical prediction guides

Battini R, Bertelloni S, Astrea G, Casarano M, Travaglini L, Baroncelli G, Pasquariello R, Bertini E, Cioni G
BMC Med Genet 2015 Jul 25;16:53. doi: 10.1186/s12881-015-0203-0. PMID: 26204956Free PMC Article
Bernard G, Chouery E, Putorti ML, Tétreault M, Takanohashi A, Carosso G, Clément I, Boespflug-Tanguy O, Rodriguez D, Delague V, Abou Ghoch J, Jalkh N, Dorboz I, Fribourg S, Teichmann M, Megarbane A, Schiffmann R, Vanderver A, Brais B
Am J Hum Genet 2011 Sep 9;89(3):415-23. doi: 10.1016/j.ajhg.2011.07.014. PMID: 21855841Free PMC Article

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