thin corpus callosum

Hypotonia, Infantile, with Psychomotor Retardation

Clinical Characteristics
Ocular Features: 

Abducens nerve palsy with characteristic strabismus (esotropia) can be present.

Systemic Features: 

Mothers may note decreased fetal movements.  Severe generalized hypotonia can be evident at birth, requiring tube feeding and respiratory assistance.  Death may occur before 6 months of age but with intense supportive care children can live for several years.  Brain imaging may show enlarged lateral ventricles and thinning of the corpus callosum in some individuals but no abnormalities in others.  Muscle biopsies can show severe myopathic changes with increased fibrosis, variation in fiber size, and small atrophic fibers.  Cardiac septal defects have been reported.  Delayed psychomotor development is a common feature.

Genetics

Homozygous mutations in the CCDC174 gene (3p25.1) are responsible for this condition so far reported in only two families with 6 children affected.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is known for this condition.

References
Article Title: 

CDC174, a novel

Volodarsky M, Lichtig H, Leibson T, Sadaka Y, Kadir R, Perez Y, Liani-Leibson
K, Gradstein L, Shaco-Levy R, Shorer Z, Frank D, Birk OS. CDC174, a novel
component of the exon junction complex whose mutation underlies a syndrome of
hypotonia and psychomotor developmental delay. Hum Mol Genet. 2015 Nov
15;24(22):6485-91.

PubMed ID: 
26358778

Basel-Vanagaite-Smirin-Yosef Syndrome

Clinical Characteristics
Ocular Features: 

The eyes appear abnormally far apart.  Ptosis, microcornea, congenital cataracts, sparse eyebrows, and strabismus are usually present.  Epicanthal folds are often seen.

Systemic Features: 

Psychomotor development is severely delayed and with delay or absence of milestones.  DTRs are often hyperactive but some infants are described as hypotonic.  Some individuals have seizures.  There may be a nevus flammeus simplex lesion on the forehead and body hair is sparse.  Cleft palate, cardiac septal defects, hypospadius, thin corpus callosum and cerebral ventricular dilation have been observed.  The upper lip may have a tented morphology with everted lower lip vermilion. A short philtrum is common. 

Genetics

A homozygous missense mutation in the MED25 gene (19q13.33) has been reported and the transmission pattern is consistent with autosomal recessive inheritance.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No known treatment has been reported.

References
Article Title: 

Homozygous MED25 mutation implicated in eye-intellectual disability syndrome

Basel-Vanagaite L, Smirin-Yosef P, Essakow JL, Tzur S, Lagovsky I, Maya I, Pasmanik-Chor M, Yeheskel A, Konen O, Orenstein N, Weisz Hubshman M, Drasinover V, Magal N, Peretz Amit G, Zalzstein Y, Zeharia A, Shohat M, Straussberg R, Monte D, Salmon-Divon M, Behar DM. Homozygous MED25 mutation implicated in eye-intellectual disability syndrome. Hum Genet. 2015 Jun;134(6):577-87.

PubMed ID: 
25792360

Spastic Paraplegia 15

Clinical Characteristics
Ocular Features: 

Yellowish flecks resembling those seen in fundus flavimaculatus are present, primarily in the macular area.   These can be present in large numbers in homozygotes with the full neurological syndrome.  Background retinal pigmentation appears clinically normal but fluorescein angiography shows a strikingly mottled picture with areas of hyper- and hypofluorescence.  Retinal flecks have also been reported in heterozygous parents.

The central macula exhibits autofluorescence.  Standard EOG and ERG recordings are normal but multifocal electroretinography shows subnormal responses in the macular area.  Visual acuity is minimally impacted.

Systemic Features: 

This is a form of spastic paraplegia with progressive spasticity primarily affecting the lower limbs.  Mental retardation (or at least cognitive impairment), dysarthria, a thin corpus callosum, and distal amyotrophy are often present.  Hearing deficits have also been described.  Some but not all patients have tremors, cerebellar ataxia, epilepsy and behavioral disturbances. Onset is between 10 and 19 years of age.  Little is known about the rate of symptom progression.

Genetics

This is an autosomal recessive disorder resulting from mutations in the ZFYVE26 gene (14q24.1).

Spastic paraplegia 7 (607259) has similar neurological features but with ptosis, optic atrophy, and nystagmus.  Congenital cataracts occur in addition to the neurological signs in spastic paraplegia 46 (614409) .

Other disorders with retinal flecks are described in Flecked Retina Syndromes.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is known.

References
Article Title: 

Fleck retina in Kjellin's syndrome

Farmer SG, Longstreth WT Jr, Kalina RE, Todorov AB. Fleck retina in Kjellin's syndrome. Am J Ophthalmol. 1985 Jan 15;99(1):45-50.

PubMed ID: 
3966518

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