Frameshift Mutation in Polar Rich Domain (PRD) of PQBP1 Gene Associated with Asymmetric Cerebellar Hemispheres: A Case Report of Renpenning Syndrome

Introduction: In 1962, Renpenning et al. published an article with 20 male patients from three generations with mental retardation. Scientists suggested that the syndrome with mutation mapped to the locus Xp11.2-p11.4 should be called Renpenning syndrome. The deletion/duplication of an AG dinucleotide on proximal Xp in the polyglutamine tract-binding protein 1 (PQBP1) gene causing frameshift in the fourth coding exon was identified as the most frequent mutation in this syndrome. Renpenning syndrome with asymmetric cerebellar hemispheres has not been reported previously. Case Presentation: In this case report, we presented an 11-year-old male with mild developmental delay and mild intellectual disability, microcephaly, dysmorphic face, short stature, and seizures. The following morphological abnormalities were detected: a wide nasal bridge, midfacial hypoplasia, short philtrum, low-set ears, low hanging columella, high palate, and narrow face. Neurological examination showed upper and lower extremities hypotonia with joint hypermobility. The patient had his first seizure at the age of seven, and he experienced a total of 10 seizures by the age 11. A systolic murmur of intensity 2/6 was present, and echocardiography showed chordae tendineae abnormalities in the left ventricle. Brain magnetic resonance imaging (MRI) showed asymmetric cerebellar hemispheres (mild right cerebellar hemisphere hypoplasia). A frameshift mutation in the polar reach domain (PRD) of the PQBPI gene (c.459 462 deIAGAG) was detected by exome sequencing. Conclusions: We showed the first case of genetically confirmed Renpenning syndrome in Serbia. Our patient had classical clinical manifestations for Renpenning syndrome as a consequence of frameshift mutation in the PRD of the PQBPI gene. To the best of our knowledge, according to the literature, this is the first patient with Renpenning syndrome with asymmetric cerebellar hemispheres (mild right cerebellar hemisphere hypoplasia).