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Phelan-McDermid syndrome (PMS, OMIM# 606232) results from either different rearrangements at the distal region of the long arm of chromosome 22 (22q13.3) or pathogenic sequence variants in the SHANK3 gene. SHANK3 codes for a structural protein that plays a central role in the formation of the postsynaptic terminals and the maintenance of synaptic structures. Clinically, patients with PMS often present with global developmental delay, absent or severely delayed speech, neonatal hypotonia, minor dysmorphic features, and autism spectrum disorders (ASD), among other findings. Here, we describe a cohort of 210 patients with genetically confirmed PMS. We observed multiple variant types, including a significant number of small deletions (

Chromosome-5p minus syndrome (5p-Sd, OMIM #123450) formerly known as Cri du Chat syndrome results from the loss of genetic material at the distal region of the short arm of chromosome 5. It is a neurodevelopmental disorder of genetic cause. So far, about 400 patients have been reported worldwide. Individuals affected by this syndrome have large phenotypic heterogeneity. However, a specific phenotype has emerged including global developmental delay, microcephaly, delayed speech, some dysmorphic features, and a characteristic and monochromatic high-pitch voice, resembling a cat’s cry. We here describe a cohort of 70 patients with clinical features of 5p- Sd characterized by means of deep phenotyping, SNP arrays, and other genetic approaches. Individuals have a great clinical and molecular heterogeneity, which can be partially explained by the existence of additional significant genomic rearrangements in around 39% of cases. Thus, our data showed significant statistical differences between subpopulations (simple 5p deletions versus 5p deletions plus additional rearrangements) of the cohort. We also determined significant “functional” differences between male and female individuals.

Phelan-McDermid syndrome (PMS, OMIM# 606232) results from either different rearrangements at the distal region of the long arm of chromosome 22 (22q13.3) or pathogenic sequence variants in the SHANK3 gene. SHANK3 codes for a structural protein that plays a central role in the formation of the postsynaptic terminals and the maintenance of synaptic structures. Clinically, patients with PMS often present with global developmental delay, absent or severely delayed speech, neonatal hypotonia, minor dysmorphic features, and autism spectrum disorders (ASD), among other findings. Here, we describe a cohort of 210 patients with genetically confirmed PMS. We observed multiple variant types, including a significant number of small deletions (<0.5 Mb, 64/189) and SHANK3 sequence variants (21 cases). We also detected multiple types of rearrangements among microdeletion cases, including a significant number with post-zygotic mosaicism (9.0%, 17/189), ring chromosome 22 (10.6%, 20/189), unbalanced translocations ( de novo or inherited, 6.4%), and additional rearrangements at 22q13 (6.3%, 12/189) as well as other copy number variations in other chromosomes, unrelated to 22q deletions (14.8%, 28/189). We compared the clinical and genetic characteristics among patients with different sizes of deletions and with SHANK3 variants . Our findings suggest that SHANK3 plays an important role in this syndrome but is probably not uniquely responsible for all the spectrum features in PMS. We emphasize that only an adequate combination of different molecular and cytogenetic approaches allows an accurate genetic diagnosis in PMS patients. Thus, a diagnostic algorithm is proposed., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Nevado, García-Miñaúr, Palomares-Bralo, Vallespín, Guillén-Navarro, Rosell, Bel-Fenellós, Mori, Milá, Campo, Barrúz, Santos-Simarro, Obregón, Orellana, Pachajoa, Tenorio, Galán, Cigudosa, Moresco, Saleme, Castillo, Gabau, Pérez-Jurado, Barcia, Martín, Mansilla, Vallcorba, García-Murillo, Cammarata-Scalisi, Gonçalves Pereira, Blanco-Lago, Serrano, Ortigoza-Escobar, Gener, Seidel, Tirado, Lapunzina and Spanish PMS Working Group.)

Chromosome-5p minus syndrome (5p-Sd, OMIM #123450) formerly known as Cri du Chat syndrome results from the loss of genetic material at the distal region of the short arm of chromosome 5. It is a neurodevelopmental disorder of genetic cause. So far, about 400 patients have been reported worldwide. Individuals affected by this syndrome have large phenotypic heterogeneity. However, a specific phenotype has emerged including global developmental delay, microcephaly, delayed speech, some dysmorphic features, and a characteristic and monochromatic high-pitch voice, resembling a cat's cry. We here describe a cohort of 70 patients with clinical features of 5p- Sd characterized by means of deep phenotyping, SNP arrays, and other genetic approaches. Individuals have a great clinical and molecular heterogeneity, which can be partially explained by the existence of additional significant genomic rearrangements in around 39% of cases. Thus, our data showed significant statistical differences between subpopulations (simple 5p deletions versus 5p deletions plus additional rearrangements) of the cohort. We also determined significant "functional" differences between male and female individuals., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Nevado, Bel-Fenellós, Sandoval-Talamantes, Hernández, Biencinto-López, Martínez-Fernández, Barrúz, Santos-Simarro, Mori-Álvarez, Mansilla, García-Santiago, Valcorba, Sáenz-Rico, Martínez-Frías and Lapunzina.)