PIEZO2 encodes a mechanically activated cation channel, which is abundantly expressed in dorsal root ganglion neuron and sensory endings of proprioceptors required for light touch sensation and proprioception in mice. Biallelic loss-of-function mutations in PIEZO2 (i.e., PIEZO2 deficiency) were recently found to cause an arthrogryposis syndrome. Sixteen patients from eight families have been reported to date. Herein we report a new case, including detailed clinical characteristics and courses as well as comprehensive neurological features. The patient was a 12-year-old girl presenting with congenital multiple contractures, progressive severe scoliosis, prenatal-onset growth impairment, motor developmental delay with hypotonia and myopathy-like muscle pathology, mild facial features, and normal intelligence. Her neurological features included areflexia, impaired proprioception, and decreased senses. Neurophysiological examination revealed decreased amplitude of sensory nerve action potentials, absent H reflex, and prolongation of central conduction times. Clinical exome sequencing revealed a novel homozygous frameshift mutation in PIEZO2 (NM_022068: c.4171_4174delGTCA: p.Val1391Lysfs*39) with no detectable mRNA expression of the gene. PIEZO2 deficiency represents a clinical entity involving characteristic neuromuscular abnormalities and physical features. Next generation sequencing-based comprehensive molecular screening and extensive neurophysiological examination could be valuable for diagnosis of the disorder.

Alternative splicing (AS) of pre-mRNAs in higher eukaryotes and several viruses is one major source of protein diversity. Usually, the following major subtypes of AS are distinguished: exon skipping, intron retention, and alternative 3\' and 5\' splice sites. Moreover, mutually exclusive exons (MXEs) represent a rare subtype. In the splicing of MXEs, two (or more) splicing events are not independent anymore, but are executed or disabled in a coordinated manner. In this review, several bioinformatics approaches for analyzing MXEs are presented and discussed. In particular, we revisit suitable definitions and nomenclatures, and bioinformatics tools for finding MXEs, adjacent and non-adjacent MXEs, clustered and grouped MXEs. Moreover, the molecular mechanisms for splicing MXEs proposed in the literature are reviewed and discussed.