[Postinfectious family case of acute necrotizing encephalopathy caused by RANBP2 gene mutation]

Roles of Nucleoporin RanBP2/Nup358 in Acute Necrotizing Encephalopathy Type 1 (ANE1) and Viral Infection

Ran Binding Protein 2 (RanBP2 or Nucleoporin358) is one of the main components of the cytoplasmic filaments of the nuclear pore complex. Mutations in the RANBP2 gene are associated with acute necrotizing encephalopathy type 1 (ANE1), a rare condition where patients experience a sharp rise in cytokine production in response to viral infection and undergo hyperinflammation, seizures, coma, and a high rate of mortality. Despite this, it remains unclear howRanBP2 and its ANE1-associated mutations contribute to pathology. Mounting evidence has shown that RanBP2 interacts with distinct viruses to regulate viral infection. In addition, RanBP2 may regulate innate immune response pathways. This review summarizes recent advances in our understanding of how mutations in RANBP2 contribute to ANE1 and discusses how RanBP2 interacts with distinct viruses and affects viral infection. Recent findings indicate that RanBP2 might be an important therapeutic target, not only in the suppression of ANE1-driven cytokine storms, but also to combat hyperinflammation in response to viral infections.

Acute Necrotizing Encephalopathy of Childhood: A Multicenter Experience in Saudi Arabia

Background: Acute necrotizing encephalopathy of childhood (ANEC) is a rapidly progressing encephalopathy characterized by fever, depressed level of consciousness, and seizures. Diagnosis depends on clinical presentation and characteristic neuroimaging findings of abnormal signal intensity involving the thalami as well as the supra and infra-tentorial areas. Treatment modalities are not well-established; empirical treatment with antibiotics and antiviral agents is the initial step, followed by steroids and immunoglobulin, as well as supportive care. Patients with ANEC have a variable prognosis, but mortality is very high. Methods: A retrospective chart review of patients diagnosed with ANEC in five tertiary centers from January 2015 to October 2018 was performed. Clinical and radiological findings, as well as the therapeutic approach and outcomes, were described. Results: Twelve children were included ranging in age from 10 months to 6 years. All patients presented with preceding febrile illness, altered level of consciousness, and seizure. Radiological features showed abnormal signals in the thalami, and five patients (41.7%) had brainstem involvement. All patients received empirical treatment with antibiotics and antiviral agents. Ten patients (83.3%) received intravenous immunoglobulin (IVIG) and IV Methylprednisolone therapy. Outcomes were variable ranging from good outcomes with minimal neurological deficits to poor outcomes and death in 25% of cases. Conclusion: ANEC is a rare fulminant disease in children. The treatment is challenging. Early interventions with the use of IVIG and IV Methylprednisolone may change the outcome; however, further studies are needed to establish a consensus guideline for the management.

Acute Postviral Encephalopathy: Pathologic and Radiologic Correlation in an Atypical Case

The authors report a case of fatal acute encephalopathy following influenza infection, with slightly atypical pathological and imaging findings. A healthy 8-year-old boy with probable recent influenza A/B infection admitted for refractory seizures was placed on phenobarbital coma and later developed hemodynamic instability. Magnetic resonance imaging revealed bilateral cerebral and cerebellar white matter lesions and microhemorrhages. Following his demise, the autopsy revealed a large area of necrosis in the right centrum semiovale with similar lesions in the temporal and cerebellar regions. Microscopically, there was extensive coagulative necrosis, compatible with necrotizing white matter encephalopathy, and neuronal loss suggesting superimposed hypoxic–ischemia. The acute progressive neurologic deterioration was partly reminiscent on acute necrotizing encephalopathy, a condition recently associated with influenza A. In acute necrotizing encephalopathy, typical brain findings are characterized by bilateral thalamic necrosis/petechiae with variable white matter edema. The somewhat atypical findings in our case can relate to superadded cardiovascular collapse and hypoxic–ischemic effects.

RANBP2 mutation and acute necrotizing encephalopathy: 2 cases and a literature review of the expanding clinico-radiological phenotype

BACKGROUND

Acute necrotising encephalopathy (ANE) is a rapidly progressive encephalopathy associated with acute viral illness. A missense mutation in nuclear pore gene RANBP2 has been identified as a major cause of familial and recurrent ANE, which is now termed as ANE1. First presentation of ANE can mimic an acute disseminated encephalomyelitis (ADEM), although ANE presents in a slightly younger age group. Identification of this disorder at radiological study is the most important determinant of the outcome. ANE1 is inherited as autosomal dominant, but shows incomplete penetrance.

METHODS

We report two female children who presented with atypical clinical presentation (afebrile) and atypical radiological presentation (lack of bilateral thalamic involvement), not fitting into the original diagnostic criteria for ANE1. Both received steroid therapy for a presumed diagnosis of ADEM and made good clinical recovery. We also reviewed the available literature on ANE1, including the clinical profile, MRI brain descriptions, CSF characteristics and common mutations.

RESULTS

A total of 59 patients are reported in patients with ANE1 were identified, the incidence of ANE was higher in younger age group (<4 yrs) as compared to ADEM 5.3 yrs (3.6-7). Male and female were equally affected. High CSF protein (>0.45 g/l) was reported in 44/47 (94%) in absence CSF pleocytosis (Cells > 5 × 10(6)/L). Neuroimaging findings showed multifocal involvement across different studies, and bilateral thalamic involvement was seen in 77% of patients.

CONCLUSION

Based on the literature review of ANE1 with RANBP2 mutation, we propose a threshold for RANBP2 mutation testing.

Familial acute necrotizing encephalopathy due to mutation in the RANBP2 gene

BACKGROUND

Acute necrotizing encephalopathy (ANE) is a rare and severe parainfectious central nervous system disease in which previously healthy children develop rapidly progressive coma following viral illness. While most ANE are sporadic, familial autosomal dominant ANE due to mutations in the RANBP2 gene has been recently reported (ANE1 or infection-induced acute encephalopathy-3 (IIAE3)). To date, only few IIAE3 families with ADANE episodes have been described.

OBJECTIVE

To report a new family with ADANE, describe clinical and radiological features and discuss differential diagnosis including Leigh syndrome or multiple sclerosis.

OBSERVATION

The family included 3 symptomatic individuals and one 59 year-old asymptomatic obligate carrier. Patients presented acute episodes of encephalopathy few days after common viral infection. Ages of onset ranged from 6 months to 5 years. Episodes not only occurred in childhood but also recurred in adulthood. Initial neurological signs included coma, focal neurological deficits and seizures. MRI showed typical necrotizing lesions primarily in the thalamus and brainstem, and in the temporal lobes and insula. CSF cell count and cultures were normal during episodes. RANBP2 gene screening identified pathogenic heterozygous c.1754C>T mutation (p.Thr585Met). Episodes led to cognitive or physical handicap in 2 patients and were fatal in one child.

CONCLUSION

IIAE3 or ADANE due to RANBP2 mutations has a large clinical heterogeneity. Our family illustrates the associated phenotypes from asymptomatic carrier to severe episodes of encephalopathy. Based on MRI features, the genetic IIAE3 diagnosis is important since prophylaxis and symptomatic management of infections may be beneficial, possibly in association with steroid or gammaglobulins.