In this report, we describe two unrelated patients with mental retardation and brachydactyly E classified as patients suffering from Albright hereditary osteodystrophy-like (AHO-like) syndrome.
Functional polymorphisms in the paternally expressed XLalphas and its cofactor ALEX decrease their mutual interaction and enhance receptor-mediated cAMP formation.
The segregation of brachydactyly with PHP 1b in this family indicates that an imprinting defect in GNAS can lead to growth plate defects, including brachydactyly and Madelung deformity.
During the last decade, some reports documented the existence of patients with POH showing additional features characteristic of AHO such as short stature and brachydactyly, previously thought to occur only in other GNAS-associated disorders.
Further studies in PHP-Ia subjects without GNAS mutations and in other brachydactyly syndromes will determine whether the pattern described is also specific.
Recently, histone deacetylase 4 (HDAC4) haploinsufficiency has been postulated to be the critical genetic mechanism responsible for the main clinical characteristics of the BDMR syndrome like developmental delay and behavioural abnormalities in combination with brachydactyly type E (BDE).
Mutation or deletion of HDAC4 causes brachydactyly mental retardation syndrome (BDMR), a disorder that includes intellectual disability, behavioral abnormalities, autism spectrum disorder, and craniofacial and skeletal anomalies, including brachydactyly type E. We present a case of familial BDMR, including a parent with mild symptoms of the disorder and a child exhibiting a more severe phenotype.
Patients presented with BDE and short stature without intellectual disability, showing that haploinsufficiency of the HDAC4 critical region may lead to a spectrum of phenotypes, ranging from isolated brachydactyly type E to BDMR.
Presented here are three individuals with haploinsufficiency of HDAC4 who have brachydactyly type E, non-dysmorphic facial features, and normal intelligence.
Haploinsufficiency of HDAC4 causes brachydactyly mental retardation syndrome, with brachydactyly type E, developmental delays, and behavioral problems.
We studied a family with autosomal-dominant Brachydactyly Type E (BDE) and identified a t(8;12)(q13;p11.2) translocation with breakpoints (BPs) upstream of PTHLH on chromosome 12p11.2 and a disrupted KCNB2 on 8q13.
The PTHLH gene encodes a parathyroid hormone-related protein (PTHrP) that is involved in the regulation of endochondral bone development, and mutations in this gene cause the type E form of brachydactyly.
Isolated brachydactyly type E (BDE), characterized by shortened metacarpals and/or metatarsals, consists in a small proportion of patients with Homeobox D13 (HOXD13) or parathyroid-hormone-like hormone (PTHLH) mutations.
The PTHLH gene within this region encodes a ligand for PTHR1: mutations in the gene encoding this receptor are associated with some cases of Ollier disease, several skeletal dysplasias including Blomstrand, Eiken, and Jansen and down-regulation of PTHLH expression in brachydactyly type E. Our findings suggest that abnormal PTHLH-PTHR1 signaling may underly this unusual form of enchondromatosis and indicate that unlike most cases of Ollier disease it is dominantly inherited.