Somatic overgrowth disorders comprise a wide range of rare conditions that present with focal enlargement of one or more tissue types. The PI3K-AKT-mTOR pathway is a signalling pathway that induces angiogenesis and cell proliferation, and is one of the most commonly overactivated signalling pathways in cancer. The PI3K-AKT-mTOR pathway can be up-regulated by genetic variants that code for proteins in this pathway, or down-regulated by proteins that inhibit the pathway. Mosaic genetic variations can result in cells that proliferate excessively in specific anatomical locations. The PIK3CA-related overgrowth spectrum (PROS) disorders include CLOVES syndrome, macrodystrophia lipomatosa, and Klippel-Trenaunay syndrome among many. The neurofibromatosis type 1 (NF1) gene encodes neurofibromin which down-regulates the PI3K-AKT-mTOR pathway. Thousands of pathological variants in the NF1 gene have been described which can result in lower-than-normal levels of neurofibromin and therefore up-regulation of the PI3K-AKT-mTOR pathway promoting cellular overgrowth. Somatic overgrowth is a rare presentation in NF1 with a wide range of clinical and radiological presentations. Hypertrophy of all ectodermal and mesodermal elements has been described in NF1 including bone, muscle, fat, nerve, lymphatics, arteries and veins, and skin. The shared signalling pathway for cellular overgrowth means that these radiological appearances can overlap with other conditions in the PIK3CA-related overgrowth spectrum. The aim of this review is to describe the genetic basis for the radiological features of NF1 and in particular compare the appearances of the somatic overgrowth disorders in NF1 with other conditions in the PIK3CA-related overgrowth spectrum.
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http://dx.doi.org/10.1007/s00256-024-04772-7 | DOI Listing |
Pediatr Blood Cancer
December 2024
Division of Pulmonary Biology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.
Background: Kaposiform lymphangiomatosis (KLA) is a complex lymphatic anomaly associated with a somatic activating NRAS p.Q61R (NRAS) mutation. KLA is characterized by malformed lymphatic vessels that can lead to effusions and coagulopathy.
View Article and Find Full Text PDFAm J Med Genet A
December 2024
Constitutional Genetics Laboratory, CHU Amiens Picardie, Amiens, France.
Proteus syndrome (PS) is a rare disorder (< 1/1000000), marked by progressive overgrowth commonly impacting the skeleton, skin, adipose tissue, and central nervous system. Clinical criteria were established in 2019. PS arises from a somatic activating variation in the AKT1 gene.
View Article and Find Full Text PDFPediatr Dermatol
December 2024
Pediatric Dermatology Department, Barcelona Children's Hospital Sant Joan de Déu, Barcelona, Spain.
Background: Many vascular anomalies harbor postzygotic somatic variants in GNAQ and GNA11; however, the phenotype of specific G-protein variants has not been well described. We report the clinical characteristics of 17 patients with a GNA11 R183C variant.
Methods: This case series is derived from a multinational cohort of vascular anomaly patients whose pathogenic mutations were identified using high-depth next generation sequencing.
Pediatr Neurol
November 2024
Department of Neonatology, Unidade Local de Saúde de Vila Nova de Gaia, Vila Nova de Gaia, Portugal.
Background: Megalencephaly-capillary malformation-polymicrogyria syndrome (MCAP) is a rare neurological disorder characterized by abnormal brain size, vascular malformations, and body overgrowth. MCAP is caused by somatic mosaicism of PIK3CA, a crucial gene in regulation of cell growth and survival, and is one of the disorders in the PIK3CA-related overgrowth spectrum.
Methods: We present a unique clinical report of a male infant diagnosed with MCAP from prenatal stages to age 12 months.
Prenat Diagn
December 2024
Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany.
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