SPATCCM

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SPATCCM
Symptoms microcephaly and significant developmental delay
Causesmutations in the SLC1A4 gene
Treatmentanti-epileptics

Spastic tetraplegia, thin corpus callosum, and progressive microcephaly (often referred to by its acronym SPATCCM) is a rare autosomal recessive disease caused by mutations in the SLC1A4 gene encoding the ASCT1 protein. The ASCT1 protein is primarily found in astrocytes in the brain where its main role is to import L-serine, a non-essential amino acid.

Contents

Symptoms and signs

Clinically, patients present with microcephaly and significant developmental delay. While some patients may be able to walk, others may not due to spasticity of limbs and hypotonic muscle tone, with progressive degeneration over time. Patients may also present with seizures, ranging from single febrile seizure to intractable epilepsy. Following brain MRI, patients may present with thin corpus callosum, decreased myelination, and/or brain atrophy. [1] These symptoms mimic that of other L-serine deficiencies [2]

Cause

There have so far been several identified mutations in the SLC1A4 gene that are linked to SPATCCM, including several frameshift (L314Hfs*42, [1] N324Tfs*29 [3] ), nonsense (Y191*, [4] W453* [5] ), duplication (L86_M88dup [6] ), and missense mutations (E256K, [1] [7] R457W, [1] G374R, [8] G381R, [9] S181F [3] ). These mutations interrupt the transport of serine from astrocytes to neurones, and across the blood brain barrier [10]

L-serine is important in brain development as it is a vital component in protein synthesis, as well as being the precursor to several essential compounds, including phosphatidylserine, sphingomyelin, glycine, and D-serine. [2]

Diagnosis

Diagnosis of SPATCCM generally relies on whole exome sequencing and the identification of a mutation in the SLC1A4 gene, while also lacking any other potential pathogenic mutations. [1]

Treatment

SPATCCM is an incurable genetic disease, however patients are often treated with anti-epileptics including vigabatrin, topiramate or clobazam, to reduce associated seizures. [4] [8] Supplementation of L-serine has also been proposed as a treatment. [1] [7] and has shown effective in a knock-in mouse model of the disease if administered prenatal and early postnatal. [10]

Epidemiology

Although most of the reported cases of SPATCCM are in people of Ashkenazi Jewish ancestry, it has also been reported in Irish, Hispanic, South Asian, Italian, Czech, Palestinian, and Pakistani ethnicities. [3] [5]

SPATCCM has a carrier frequency of 0.7% in the Ashkenazi Jewish population. [1]

Related Research Articles

Serine is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group, a carboxyl group, and a side chain consisting of a hydroxymethyl group, classifying it as a polar amino acid. It can be synthesized in the human body under normal physiological circumstances, making it a nonessential amino acid. It is encoded by the codons UCU, UCC, UCA, UCG, AGU and AGC.

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<span class="mw-page-title-main">Pitt–Hopkins syndrome</span> Medical condition

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<span class="mw-page-title-main">Kohlschütter–Tönz syndrome</span> Medical condition

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<span class="mw-page-title-main">Chudley–Mccullough syndrome</span> Medical condition

Chudley–Mccullough syndrome is a rare genetic disorder which is characterized by bilateral congenital hearing loss associated with brain malformations. It is a type of syndromic deafness.

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Severe intellectual disability-progressive spastic diplegia syndrome is a rare novel genetic disorder characterized by severe intellectual disabilities, ataxia, craniofacial dysmorphisms, and muscle spasticity. It is a type of autosomal dominant syndromic intellectual disability.

<span class="mw-page-title-main">X-linked complicated corpus callosum dysgenesis</span> Medical condition

X-linked complicated corpus callosum dysgenesis is a genetic disorder characterized by dysplasia, hypoplasia or agenesis of the corpus callosum alongside variable intellectual disability and spastic paraplegia. Only 13 cases have been described in medical literature. Transmission is X-linked recessive. It is the mildest subtype of L1 syndrome.

References

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