Reyhaneh Kameli - Myelin Disorders Clinic, Pediatric Neurology Division, Children's Medical Center, Pediatrics Center of Excellence, Tehran University of Medical Sciences, Tehran, Iran
Man Amanat
Zahra Rezaei
Sareh Hosseionpour
Sedigheh Nikbakht
Houman Alizadeh - Department of Pediatrics, Division of Pediatric Radiology, Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran

Background: 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 recessiveneurogenetic disorder with psychomotor delay as its main clinical symptom. The clinical findings can be similar to congenital cytomegalovirus (CMV) infectionand Aicardi-Goutieres syndrome (AGS).Methods: Herein, we presented a patient with motor delay, neurological regression, infrequent seizures and microcephaly at 5 months of age. Brain imagingshowed white matter involvement, calcification and anterior temporal cysts. Basic metabolic tests, serum and urine CMV polymerase chain reaction (PCR) wererequested. According to clinical and imaging findings, screening of RNASET2 and RMND1 genes were performed. The clinical data and magnetic resonanceimaging (MRI) findings of previous reported individuals with RNASET2-deficient leukodystrophy were also reviewed and compared to the findings of our patient.Results: Brain MRI findings were suggestive of RNASET2-deficient leukoencephalopathy, AGS and CMV infection. Basic metabolic tests were normal and CMVPCR was negative. Molecular study revealed a novel homozygous variant of c.233C > A; p.Ser78Ter in exon 4 of RNASET2 gene compatible with the diagnosisof RNASET2-deficient leukoencephalopathy. Conclusions: RNASET2-deficiency is a possible diagnosis in an infant presented with a static leukoencephalopathyand white matter involvement without megalencephaly. Due to overlapping clinical and radiologic features of RNASET2-deficient leukoencephalopathy, AGS andcongenital CMV infections, molecular study as an important and helpful diagnostic tool should be considered avoid misdiagnosis.

Ribonuclease, RNASET2-deficienct leukoencephalopathy, Cystic leukoencephalopathy, Aicardi-Goutieres syndrome, Congenital cytomegalovirusinfection