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Ophthalmic phenotype of TCIRG1 gene mutations in Chinese infantile malignant osteopetrosis

Wenhong Cao1,2, Wenbin Wei2, Qian Wu1

  • 1Department of Ophthalmology, Beijing Children's Hospital, National Center for Children's Health, National Key Discipline of Pediatrics, Capital Medical University, Beijing, China.

BMJ Open Ophthalmology
|December 13, 2018
PubMed

Insights

Frameshift mutations in TCIRG1 cause more severe optic canal stenosis and optic atrophy in infantile malignant osteopetrosis patients. No differences in optic nerve conduction block were observed between mutation types.

Area of Science:

  • Ophthalmology
  • Genetics
  • Pediatrics

Background:

  • Infantile malignant osteopetrosis (IMO) is a rare genetic disorder.
  • Mutations in the T-cell immune regulator 1 (TCIRG1) gene are a common cause of autosomal recessive osteopetrosis.
  • Ophthalmic complications are frequent in IMO, impacting vision and neurological function.

Purpose of the Study:

  • To investigate the specific ophthalmic phenotypes associated with TCIRG1 mutations in Chinese infants with IMO.
  • To compare the clinical features and severity of ocular manifestations between different types of TCIRG1 mutations (frameshift vs. point mutations).

Main Methods:

  • A cohort of 27 Chinese infants with TCIRG1-related osteopetrosis was studied.
  • Direct DNA sequencing was used to identify mutation types: 12 with frameshift (group F) and 15 with point mutations (group P).
  • Ophthalmic examinations included assessment of gaze quality, optic atrophy, optic canal stenosis, and Flash visual-evoked potential (FVEP).

Main Results:

  • Frameshift mutations were associated with earlier onset (1.8 months) compared to point mutations (4.3 months).
  • Severe ophthalmic phenotypes, including poor gaze quality (92% vs. 53%) and optic atrophy (67% vs. 20%), were significantly more prevalent in the frameshift group.
  • Optic canal stenosis was more pronounced in frameshift mutation cases (average diameter 1.45 mm vs. 1.87 mm).
  • FVEP showed abnormal waveforms in a higher proportion of eyes with frameshift mutations (42% vs. 17%).

Conclusions:

  • TCIRG1 frameshift mutations lead to more severe optic canal stenosis and optic atrophy in Chinese IMO patients.
  • Despite differences in structural damage, no significant difference in optic nerve conduction block was found between frameshift and point mutation groups.
Abstract

Keywords:
mutationosteopetrosisphenotype

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