Abstract
BackgroundRibonucleases (RNases) are crucial for degradation of ribosomal RNA (rRNA). RNASET2 as a subtype of RNASEs is a 256 amino acid protein, encoded by RNASET2 gene located on chromosome six. Defective RNASET2 leads to RNASET2-deficient leukoencephalopathy, a rare autosomal recessive neurogenetic disorder with psychomotor delay as its main clinical symptom. The clinical findings can be similar to congenital cytomegalovirus (CMV) infection and Aicardi-Goutieres syndrome (AGS).MethodsHerein, we presented a patient with motor delay, neurological regression, infrequent seizures and microcephaly at 5 months of age. Brain imaging showed white matter involvement, calcification and anterior temporal cysts. Basic metabolic tests, serum and urine CMV polymerase chain reaction (PCR) were requested. According to clinical and imaging findings, screening of RNASET2 and RMND1 genes were performed. The clinical data and magnetic resonance imaging (MRI) findings of previous reported individuals with RNASET2-deficient leukodystrophy were also reviewed and compared to the findings of our patient.ResultsBrain MRI findings were suggestive of RNASET2-deficient leukoencephalopathy, AGS and CMV infection. Basic metabolic tests were normal and CMV PCR was negative. Molecular study revealed a novel homozygous variant of c.233C > A; p.Ser78Ter in exon 4 of RNASET2 gene compatible with the diagnosis of RNASET2-deficient leukoencephalopathy.ConclusionsRNASET2-deficiency is a possible diagnosis in an infant presented with a static leukoencephalopathy and white matter involvement without megalencephaly. Due to overlapping clinical and radiologic features of RNASET2-deficient leukoencephalopathy, AGS and congenital CMV infections, molecular study as an important and helpful diagnostic tool should be considered to avoid misdiagnosis.
Highlights
Ribonucleases (RNases) are crucial for degradation of ribosomal RNA
Mutation of RNASET2 gene leads to the accumulation of undigested ribosomal RNA (rRNA) in lysosomes within the central nervous system which can cause a rare type of leukoencephalopathy [5]
Patient selection and ethical committee approval We presented a genetically confirmed case of RNASET2deficient leukoencephalopathy included in our database (Iranian Neurometabolic Disorders Registry, INMR); consisted of 285 individuals with different types of heritable white matter disorders
Summary
Ribonucleases (RNases) are crucial for degradation of ribosomal RNA (rRNA). RNASET2 as a subtype of RNASEs is a 256 amino acid protein, encoded by RNASET2 gene located on chromosome six. Defective RNASET2 leads to RNASET2-deficient leukoencephalopathy, a rare autosomal recessive neurogenetic disorder with psychomotor delay as its main clinical symptom. Ribonucleases (RNases) are intracellular enzymes, catalyzing the degradation of ribosomal ribonucleic acid (rRNA). These enzymes are divided into different subtypes with multiple function [1–3]. RNASET2 as a defined subtype of RNases performs diverse roles in different species; including phosphate scavenging following nutritional stress and acting as cytotoxic agent. Mutation of RNASET2 gene leads to the accumulation of undigested rRNA in lysosomes within the central nervous system which can cause a rare type of leukoencephalopathy [5]
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