Variable clinical presentation of split hand/foot malformation syndrome in a family with microduplication of 10q24.32: a case report

SHFM (Split Hand/Foot Malformation) is a heterogeneous group of disorders characterized by the presence of clefts in the hands and feet, along with syndactyly of the digits. In this article, we describe a family in which two members exhibit characteristic developmental abnormalities associated with SHFM, presenting with variable clinical features. Using whole-genome sequencing, we identified a microduplication of a chromosomal segment on locus 10q24.32, specifically spanning positions 102934495 to 103496555, encompassing genes BTRC, POLL, FBXW4 and LBX1 in the proband. Genomic duplications, including these genes, were previously described in patients diagnosed with the third type of SHFM. We validated the presence of this structural rearrangement in 7 family members, including the proband and the proband's father. Remarkably, further investigation demonstrated that the detected duplication exhibits a mosaic state in the phenotypically normal paternal grandmother of the proband, thereby providing a plausible explanation for the absence of a pathological phenotype in her.

Case report: Unusual episodic myopathy in a patient with novel homozygous deletion of first coding exon of MICU1 gene

We present a patient with unusual episodes of muscular weakness due to homozygous deletion of exon 2 in the MICU1 gene. Forty-three patients from 33 families were previously described with homozygous and compound heterozygous, predominantly loss of function (LoF) variants in the MICU1 gene that lead to autosomal recessive myopathy with extrapyramidal signs. Most described patients developed muscle weakness and elevated CK levels, and half of the patients had progressive extrapyramidal signs and learning disabilities. Our patient had a few severe acute episodes of muscle weakness with minimal myopathy features between episodes and a strongly elevated Creatinine Kinase (CK). Whole exome sequencing (WES) was performed and the homozygous deletion of exon 2 was suspected. To validate the diagnosis, we performed an RNA analysis of all family members. To investigate the possible impact of this deletion on the phenotype, we predicted a new Kozak sequence in exon 4 that could lead to the formation of a truncated MICU1 protein that could partly interact with MCU protein in a mitochondrial Ca2+ complex. We suspect that this unusual phenotype of the proband with MICU1-related myopathy could be explained by the presence of the truncated but partly functional protein. This work helps to define the clinical polymorphism of MICU1 deficiency better.

Complex Transposon Insertion as a Novel Cause of Pompe Disease

Pompe disease (OMIM#232300) is an autosomal recessive lysosomal storage disorder caused by mutations in the GAA gene. According to public mutation databases, more than 679 pathogenic variants have been described in GAA, none of which are associated with mobile genetic elements. In this article, we report a novel molecular genetic cause of Pompe disease, which could be hardly detected using routine molecular genetic analysis. Whole genome sequencing followed by comprehensive functional analysis allowed us to discover and characterize a complex mobile genetic element insertion deep in the intron 15 of the GAA gene in a patient with infantile onset Pompe disease.