Germline 3p22.1 microdeletion encompassing RPSA gene is an ultra-rare cause of isolated asplenia

Abstract

Background: Isolated Congenital Asplenia (ICA, OMIM #271400) is a rare, life-threatening abnormality causing immunodeficiency, which is characterized by the absence of a spleen. Diagnosis should be completed in early childhood and antibiotic prophylaxis applied with additional vaccinations.

Case presentation: We report the case of a six-month old girl with hematologic abnormalities and asplenia documented in imaging, with Howell-Jolly bodies in peripheral blood smear. Targeted Next Generation Sequencing screening did not reveal any pathogenic variant in genes associated with congenital asplenia. Since absence of the spleen was found by imaging, high-resolution copy number variations detection was also performed using genomic Single Nucleotide Polymorphism microarray: a heterozygous 337.2 kb deletion encompassing the RPSA gene was observed, together with SLC25A38, SNORA6, SNORA62 and MOBP genes. Despite haploinsufficiency of SLC25A38, SNORA6, SNORA62 and MOBP, no change in the clinical picture was observed. A search of available CNV databases found that a deletion of the RPSA locus seems to be unique and only duplications were found in this region with the frequency of less than 0.02%.

Conclusions: Copy number variations in RPSA gene locus are ultrarare cause of isolated asplenia. Furthermore, since the patient does not present any concomitant clinical features, it would appear that haploinsufficiency of SLC25A38, SNORA6, SNORA62 and MOBP genes does not affect the phenotype of patients. However, to confirm this thesis a longer follow-up of the patient's development is needed.

Keywords: Deletion; ICA; Isolated congenital asplenia; RPSA.

Fig. 1

Laboratory and genetic findings in the patient with isolated asplenia. A Peripheral blood smear with Howell–Jolly bodies (indicated with arrows); B Heterozygous deletion at the short arm of chromosome 3 with a size of 337.2 kbp (arr[GRCh37] 3p22.2p22.1(39357060_39694267) × 1) encompassing the RPSA gene (red arrow)