Novel frameshift variant in the PCNT gene associated with Microcephalic Osteodysplastic Primordial Dwarfism (MOPD) Type II and small kidneys

Clinical application of whole exome sequencing technology in small-for-gestational-age children

AIM

To apply whole exome sequencing (WES) for molecular diagnosis of small-for-gestational-age (SGA) children.

METHODS

We retrospectively analyzed the data of 60 SGA children in our hospital, and performed developmental assessment, laboratory tests, imaging tests, and whole exome sequencing (WES), which were combined with clinical phenotypes to clarify the pathogenicity of the variant genes in the children.

RESULTS

Sixty SGA children were tested, and pathogenic SGA was detected at relatively high frequencies on chromosomes 7, 8, and 22. Of these, karyotype analysis clearly suggested developmental disorders in 4 patients. Also, a case of Wiedemann-Steiner syndrome due to a de novo nonsense variant in the KMT2A gene was detected.

CONCLUSIONS

The use of WES testing technology to increase the diagnosis rate of children with special SGA is conducive to the correct diagnosis and treatment of such children.

Genetic Primary Microcephalies: When Centrosome Dysfunction Dictates Brain and Body Size

Primary microcephalies (PMs) are defects in brain growth that are detectable at or before birth and are responsible for neurodevelopmental disorders. Most are caused by biallelic or, more rarely, dominant mutations in one of the likely hundreds of genes encoding PM proteins, i.e., ubiquitous centrosome or microtubule-associated proteins required for the division of neural progenitor cells in the embryonic brain. Here, we provide an overview of the different types of PMs, i.e., isolated PMs with or without malformations of cortical development and PMs associated with short stature (microcephalic dwarfism) or sensorineural disorders. We present an overview of the genetic, developmental, neurological, and cognitive aspects characterizing the most representative PMs. The analysis of phenotypic similarities and differences among patients has led scientists to elucidate the roles of these PM proteins in humans. Phenotypic similarities indicate possible redundant functions of a few of these proteins, such as ASPM and WDR62, which play roles only in determining brain size and structure. However, the protein pericentrin (PCNT) is equally required for determining brain and body size. Other PM proteins perform both functions, albeit to different degrees. Finally, by comparing phenotypes, we considered the interrelationships among these proteins.

Case Report: short stature, kidney anomalies, and cerebral aneurysms in a novel homozygous mutation in the PCNT gene associated with microcephalic osteodysplastic primordial dwarfism type II

We report the case of a boy (aged 3 years and 7 months) with severe growth failure (length: -9.53 SDS; weight: -9.36 SDS), microcephaly, intellectual disability, distinctive craniofacial features, multiple skeletal anomalies, micropenis, cryptorchidism, generalized hypotonia, and tendon retraction. Abdominal US showed bilateral increased echogenicity of the kidneys, with poor corticomedullary differentiation, and a slightly enlarged liver with diffuse irregular echotexture. Initial MRI of the brain, performed at presentation, showed areas of gliosis with encephalomalacia and diffused hypo/delayed myelination, and a thinned appearance of the middle and anterior cerebral arteries. Genetic analysis evidenced a novel homozygous pathogenic variant of the pericentrin (PCNT) gene. PCNT is a structural protein expressed in the centrosome that plays a role in anchoring of protein complexes, regulation of the mitotic cycle, and cell proliferation. Loss-of-function variants of this gene are responsible for microcephalic osteodysplastic primordial dwarfism type II (MOPDII), a rare inherited autosomal recessive disorder. The boy died at 8 years of age as a result of an intracranial hemorrhage due to a cerebral aneurism associated with the Moyamoya malformation. In confirmation of previously published results, intracranial anomalies and kidney findings were evidenced very early in life. For this reason, we suggest including MRI of the brain with angiography as soon as possible after diagnosis in follow-up of MODPII, in order to identify and prevent complications related to vascular anomalies and multiorgan failure.