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Prospective study of pediatric patients presenting with idiopathic infantile nystagmus-Management and molecular
Nancy Aychoua1,2, Elena Schiff1, Samantha Malka1
1Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.
Insights
Idiopathic infantile nystagmus (IIN) is an inherited eye condition. Genetic testing identified mutations in FRMD7 and GPR143 genes in 36% of patients, expanding the known genetic causes.
Area of Science:
- Ophthalmology
- Clinical Genetics
- Pediatric Neurology
Background:
- Idiopathic infantile nystagmus (IIN) is an inherited disorder presenting in early infancy.
- Diagnosis is challenging, requiring exclusion of serious underlying systemic or neurological conditions.
- Genetic factors, particularly mutations in the FRMD7 gene, are primary causes of IIN.
Purpose of the Study:
- To report clinical and genetic findings in a cohort of patients with IIN.
- To expand the understanding of the genetic spectrum of IIN.
- To emphasize the importance of integrated care and advanced genetic testing in IIN diagnosis.
Main Methods:
- Retrospective analysis of 22 unrelated IIN patients seen between 2016-2022.
- Multimodal ocular investigations and next-generation sequencing (WGS or targeted panels).
- Clinical data and genetic outcomes were collected and analyzed.
Main Results:
- A molecular diagnosis was confirmed in 36% (8/22) of patients.
- Eight mutations were identified across two genes: seven in FRMD7 (including one novel variant) and one in GPR143.
- Diverse ethnicities were represented in the patient cohort.
Conclusions:
- This study broadens the known mutational spectrum for IIN.
- Integrated care pathways and comprehensive genetic testing are crucial for accurate IIN diagnosis.
- Identifying genetic causes aids in ruling out other pathologies and provides diagnostic clarity.
Abstract:
Idiopathic infantile nystagmus (IIN) is an inherited disorder occurring in the first 6 months of life, with no underlying retinal or neurological etiologies and is predominantly caused by mutations in the FRMD7 gene. IIN poses a diagnostic challenge as underlying pre-symptomatic "multisystem" disorders varying from benign to life-threatening should first be ruled out before nystagmus can be labeled as idiopathic. A multidisciplinary approach including multimodal ocular investigations and next-generation sequencing with whole-genome sequencing (WGS) or targeted gene panel testing is required to delineate the exact etiology. We report the clinical and genetic outcomes of 22 patients, from 22 unrelated families of diverse ethnicities, with IIN seen in the ocular genetics service at Moorfields Eye Hospital NHS Foundation Trust between 2016 and 2022. Thirty-six percent (8/22) received a confirmed molecular diagnosis with eight mutations identified in two genes (seven in FRMD7 including one novel variant c.706_707del; p. [Lys236Alafs*66], and one in GPR143). This study expands the mutational spectrum of IIN and highlights the significant role of an integrated care pathway and broader panel testing in excluding underlying pathologies.
