Acute infection-induced encephalopathy-3 (IIAE3) is a rapidly progressive encephalopathy associated with acute viral illnesses, thought to be caused by a mutation in the RANBP2 gene on chromosome 2q12. This has also been described as ANE1. Patients with mutations of the RANBP2 gene have been associated with familial and recurrent Acute necrotizing encephalitis (ANE). The first presentation of ANE can mimic Acute disseminated encephalomyelitis however ANE presents at a slightly younger age. The incidence of ANE was higher in a younger age group (< 4 years) as compared to ADEM 5.3 years (3.6-7).
On imaging patients may have
1. Increased T2 signal in the thalami (33/42, 79% of cases with 2/3 being symmetric at first presentation)
2. Symmetric multifocal lesions in the
Medial temporal lobes / insular cortex, amygdala hippocampus complex, claustrum or external capsule (33/42, 79% of cases, with 20% being symmetric)
Brainstem (32/42, 76%)
Cerebellum (2/15, 13%)
Spinal cord (4/27, 15%)
The periventricular white matter is normal. The basal ganglia are usually normal.
References
1. Singh RR et al., RANBP2 mutation and acute necrotizing encephalopathy: 2 cases and a literature review of the expanding clinico-radiological phenotype. European J of Paediatric Neurology 19(2015):106-113