Introduction
Recent studies have highlighted the importance of comprehensive genetic testing in neonatal and pediatric intensive care units, where genetic disorders are frequently associated with morbidity and mortality. Advances in availability, diagnostic yield, and turnaround time of rapid genome sequencing (rGS) have allowed for improvements in patient care and timely management changes. However, interpretation of results can be challenging, especially in the setting of variants of uncertain significance (VUS) or when novel disease-associated genes are identified. This can be true when evaluating infants, as full phenotypic features may not be present at the time of initial evaluation, or when few cases exist in the literature.

Case Presentation
A 3-month-old female with significant postnatal growth restriction and a recent COVID infection was admitted to the hospital with abnormal eye movements and progressive feeding dysfunction requiring nasogastric (NG) tube feeds. She had a previous admission for similar where she was started on NG tube feeds with improvement in her weight. Ophthalmology attributed her eye movements to possible malnutrition. A week later, she returned for same with additional concerns for hypotonia and developmental delay, and she was noted to have mild dysmorphic features.

Diagnostic Workup
Given the severity of her feeding dysfunction, trio rGS, Russell Silver Syndrome (RSS) methylation analysis via EpiSign, and biochemical testing, including carnitine and acylcarnitine profiles, plasma amino acids, and urine organic acids, were recommended. Biochemical testing did not suggest an inborn error of metabolism and RSS methylation analysis was normal. Brain MRI/MRS revealed no acute abnormalities. rGS identified a heterozygous de novo ANO4 c.1569C>A variant, initially classified as a VUS. Although ANO4 had recently been linked to autosomal dominant sporadic encephalopathy or familial epilepsy, our patient had not experienced seizures and it was felt her symptoms were not specific enough to be diagnostic. 

Treatment and Management
Her feeding difficulties persisted and ultimately, she was transitioned to nasojejunal (NJ) tube feeding and proton pump inhibitor (PPI) therapy was started for severe gastroesophageal reflux. Her eye movements were not felt to be seizures. During this time, further review of the ANO4 publication showed one published individual had the same variant as our patient and the variant was upgraded to likely pathogenic.

 

Outcome and Follow-Up
One month later, she presented with progressive apneic episodes leading to respiratory failure requiring intubation. Despite empiric treatment for presumed aspiration pneumonia, her respiratory failure persisted, and concerns about central apnea arose. A tracheostomy was placed to manage her acute-on-chronic respiratory failure. She continues to struggle with reflux and emesis, with plans for a gastrojejunostomy tube placement. Multiple EEGs did not show epileptiform discharges, and she remains off antiepileptic medications.

Discussion
Identification of a de novo ANO4 variant provided crucial diagnostic information and facilitated timely management discussions. However, since the testing labs used different reference sequences, it was not initially recognized that the variant in our patient was the same as a published patient. Additionally, as ANO4-related disorder is characterized as a Developmental and Epileptic Encephalopathies (DEEs), there was concern regarding the ability to provide a diagnosis in a patient without seizures. Currently there are only 7 patients described with ANO4-related disorder and the one individual with this specific variant died in childhood. This scarcity of data, combined with the absence of reported seizures in our patient, made counseling and management recommendations particularly challenging and the family also expressed difficulty in accepting the diagnosis, given the lack of clear clinical manifestations. 

 

Conclusion
Advances in genetic testing have increased diagnostic yield and shortened turnaround times, significantly impacting patient care. However, variant interpretation remains challenging, particularly for newly identified genes with limited phenotypic and prognostic data. These complexities can create difficulties when providing guidance to families and healthcare teams.