Generalized hypotonia, and Optic disc pallor

Optic atrophy-intellectual disability syndrome is a rare, hereditary, syndromic intellectual disability characterized by developmental delay, intellectual disability, and significant visual impairment due to optic nerve atrophy, optic nerve hypoplasia or cerebral visual impairment. Other common clinical signs and symptoms are hypotonia, oromotor dysfunction, seizures, autism spectrum disorder, and repetitive behaviors. Dysmorphic facial features are variable and nonspecific.

OPTIC ATROPHY-INTELLECTUAL DISABILITY SYNDROME Is also known as bbsoas|bosch-boonstra-schaaf optic atrophy syndrome

• Intellectual disability
• Global developmental delay
• Generalized hypotonia
• Nystagmus
• Strabismus

SOURCES: OMIM ORPHANET MENDELIAN

• Intellectual disability
• Global developmental delay
• Generalized hypotonia
• Hearing impairment
• Ataxia

SOURCES: OMIM MENDELIAN

Autosomal recessive congenital cerebellar ataxia due to GRID2 deficiency is a rare, genetic, slowly progressive neurodegenerative disease resulting from GRID2 deficiency characterized by motor, speech and cognitive delay, hypotonia, truncal and appendicular ataxia, and eye movement abnormalities (tonic upgaze, nystagmus, oculomotor apraxia). Intention tremor may also be associated. Brain imaging reveals progressive cerebellar atrophy with cerebellar flocculus particularly affected.

AUTOSOMAL RECESSIVE CONGENITAL CEREBELLAR ATAXIA DUE TO GRID2 DEFICIENCY Is also known as autosomal recessive congenital cerebellar ataxia due to ionotropic glutamate receptor delta-2 subunit deficiency|scar18

• Intellectual disability
• Seizures
• Global developmental delay
• Generalized hypotonia
• Ataxia

SOURCES: ORPHANET OMIM MENDELIAN

• Intellectual disability
• Global developmental delay
• Generalized hypotonia
• Ataxia
• Muscular hypotonia

SOURCES: MESH OMIM MENDELIAN

Early infantile epileptic encephalopathy-47 is a neurologic disorder characterized by onset of intractable seizures in the first days or weeks of life. EEG shows background slowing and multifocal epileptic spikes, and may show hypsarrhythmia. Most patients have developmental regression after seizure onset and show persistent intellectual disability and neurologic impairment, although the severity is variable. Treatment with phenytoin, a voltage-gated sodium channel blocker, may be beneficial (summary by Guella et al., 2016).For a general phenotypic description and a discussion of genetic heterogeneity of EIEE, see EIEE1 (OMIM ).

• Intellectual disability
• Seizures
• Global developmental delay
• Generalized hypotonia
• Microcephaly

SOURCES: OMIM MENDELIAN

Multiple mitochondrial dysfunctions syndrome-6 is an autosomal recessive severe neurodegenerative disorder with onset in early childhood. Affected individuals may have initial normal development, but show neurologic regression in the first year of life. They have hypotonia, inability to walk, poor speech, intellectual disability, and motor abnormalities, such as ataxia, dystonia, and spasticity. Some patients may die in childhood. Laboratory evidence indicates that the disorder results from mitochondrial dysfunction (summary by Vogtle et al., 2018).For a general description and a discussion of genetic heterogeneity of multiple mitochondrial dysfunctions syndrome, see MMDS1 (OMIM ).

• Intellectual disability
• Seizures
• Global developmental delay
• Generalized hypotonia
• Microcephaly

SOURCES: OMIM MENDELIAN

Mitochondrial complex III deficiency, nuclear type 8, is an autosomal recessive disorder characterized by progressive neurodegeneration with onset in childhood. Affected individuals may have normal or delayed early development, and often have episodic acute neurologic decompensation and regression associated with febrile illnesses. The developmental regression results in variable intellectual disability and motor deficits, such as hypotonia, axial hypertonia, and spasticity; some patients may lose the ability to walk independently. Laboratory studies show increased serum lactate and isolated deficiency of mitochondrial complex III in skeletal muscle and fibroblasts. Brain imaging shows a characteristic pattern of multifocal small cystic lesions in the periventricular and deep cerebral white matter (summary by Dallabona et al., 2016).For a discussion of genetic heterogeneity of mitochondrial complex III deficiency, see MC3DN1 (OMIM ).

• Intellectual disability
• Global developmental delay
• Generalized hypotonia
• Ataxia
• Nystagmus

SOURCES: OMIM MENDELIAN

Autosomal recessive axonal CMT2A2B is a neurologic disorder characterized by onset of peripheral neuropathy in the first years of life. Patients have difficulty walking due to distal muscle weakness; upper limbs may also be affected. Sensory impairment is more variable. Patients often have optic atrophy (summary by Polke et al., 2011).

• Generalized hypotonia
• Hearing impairment
• Scoliosis
• Failure to thrive
• Muscle weakness

SOURCES: OMIM MENDELIAN

Autosomal recessive spastic paraplegia type 75 is a rare, complex hereditary spastic paraplegia characterized by an early onset and slow progression of spastic paraplegia associated with cerebellar signs, nystagmus, peripheral neuropathy, extensor plantar responses and borderline to mild intellectual disability. Additional features of hypo- or areflexia, mild upper limb involvement and significant visual impairment (optic atrophy, vision loss, astigmatism) have been reported.

AUTOSOMAL RECESSIVE SPASTIC PARAPLEGIA TYPE 75 Is also known as spg75

• Intellectual disability
• Global developmental delay
• Generalized hypotonia
• Nystagmus
• Spasticity

SOURCES: OMIM ORPHANET MENDELIAN

Spastic paraplegia, intellectual disability, nystagmus, and obesity (SINO) is an autosomal dominant neurologic disorder characterized by rapid growth in infancy, global developmental delay, spastic paraplegia, variable ophthalmologic defects, and dysmorphic facial features (summary by Josifova et al., 2016).

SPASTIC PARAPLEGIA-INTELLECTUAL DISABILITY-NYSTAGMUS-OBESITY SYNDROME Is also known as sino syndrome

• Intellectual disability
• Global developmental delay
• Generalized hypotonia
• Nystagmus
• Abnormal facial shape

SOURCES: ORPHANET OMIM MENDELIAN