Familial Acute Necrotizing Encephalopathy: Evidence From Next Generation Sequencing of Digenic Inheritance

Infection-induced acute encephalopathies (IIAEs) are a group of neurologic disorders caused post infection. They are of 8 types, 6 of which are herpes specific, whereas IIAE3 and IIAE4 can be triggered by infections additional to herpeslike influenza, enterovirus, etc. IIAE3 is also known as acute necrotizing encephalopathy type 1, which is a rare type of encephalopathy that occurs following an infection in infancy or early childhood. Symptoms include fever, cough, congestion, vomiting, and diarrhea followed by seizures, hallucination, ataxia, and abnormal muscle tone, and sometimes it leads to untimely death. Here, we describe a familial case where 3 siblings were clinically diagnosed with acute necrotizing encephalopathy 1. Genetic testing revealed 2 heterozygous variations: RANBP2 c.5249C>G, p.P1750 R, and CPT2 c.365C>T, p.S122F. Variants in RANBP2 and CPT2 have been individually known to be associated with IIAE3 and IIAE4, respectively. Segregation analysis revealed that the RANBP2 variant was inherited from the father and the CPT2 variant from the mother. This case qualifies to be the first of its kind where digenic inheritance (ie, DNA sequence variants in 2 genes are required for the pathogenic phenotypes) appears to cause a lethal class of acute necrotizing encephalopathy.