On this page, you will find information about genetic changes that were identified in a UDN participant.

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Date of Report

Nov 09, 2017

Full Name

Sep (O-phosphoserine) tRNA:Sec (selenocysteine) tRNA synthase

Chromosome 4 (4p15.2)


The SEPSECS gene codes for an enzyme important in the formation of a transfer RNA (tRNA). This tRNA is involved in the production of a protein building block called selenocysteine (Genetics Home Reference).

Database Links

GeneCards: GC04M025121

Genetics Home Reference: SEPSECS gene

NCBI Gene: 51091

OMIM: 613009

UniProtKB/Swiss-Prot: Q9HD40

Clinical Significance

Changes in the SEPSECS gene were identified in a UDN participant with pontocerebellar hypoplasia, type 2D. She was found to carry the following genetic changes in the SEPSECS gene: c.808dupG & a splicing defect.

Inheritance Pattern Autosomal recessive
Position Chr4: 25146751_25146752 insC & splicing defect
Transcript NM_016955.3
DNA Change c.808dupG & splicing defect
Protein Change p.Ala270GlyfsTer5 & N/A

At birth, the patient had low muscle tone (hypotonia) and poor head control. She was initially able to breast feed, but stopped at the age of 7 months. At 8 months, an MRI showed abnormal brain findings (cerebellar atrophy). She was admitted to the hospital at the age of 10 months for sleep problems and abnormal breathing (stridor).

Currently the patient has developmental delay and still struggles with head control. She does recognize her mother and has a social smile, but appears to have vision impairment (cortical visual impairment). She also sweats a lot and needs a G tube for feeding. At times, she has low blood glucose levels (hypoglycemia).

Some of her other features include:

  • Muscle weakness
  • Weak facial muscles (myopathic facies)
  • Impaired voluntary movements (dyskinesia)
  • Intellectual disability
  • Difficulty growing after birth (failure to thrive)
  • Poor appetite
  • Sleep disturbance
  • Irritability
  • Abnormality of specific brain regions (cerebellar hypoplasia and atrophy, cerebral hypomyelination, hypoplasia of the corpus callosum)
  • Abnormal electrical activity of the brain (EEG with persistent abnormal rhythmic activity)
  • Abnormality of the eye (abnormality of the retina and optic disc)
  • Repetitive eye movements (nystagmus)
  • Abnormality of vision (reduced visual acuity and cortical visual impairment)
  • Eyes turned outward (exotropia)
  • Drooped upper eyelids (ptosis)
  • Breathing dysregulation
  • Hand clenching
  • Decreased urine output
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