Background and Clinical Significance: Familial short stature is a common reason for referral in clinical genetics. While often attributed to a single genetic cause, genetic heterogeneity can complicate diagnosis and management. This report describes a family in which three distinct pathogenic variants in SHOX, PDE4D and ACAN caused overlapping phenotypes of familial short stature. Case Presentation: Clinical, radiological and molecular data were collected retrospectively at the Reference Centre for Constitutional Bone Diseases at Montpellier University Hospital. Targeted gene panels, whole genome sequencing and Sanger sequencing were employed to identify pathogenic variants. Variant interpretation followed the guidelines of the American College of Medical Genetics. A pathogenic SHOX variant (c.452G>A; p.Ser151Asn) was identified in the proband and her mother, which is consistent with dyschondrosteosis. A de novo PDE4D variant (c.671C>T; p.Thr224Ile) was identified in a cousin presenting with syndromic acrodysostosis. An ACAN splice variant (c.6833-1G>A) was detected in several family members and is associated with short stature and skeletal anomalies. An individual carrying both the SHOX and ACAN variants exhibited a more severe phenotype, suggesting an additive effect. Conclusions: This case study highlights the importance of systematic molecular investigations in families with overlapping yet heterogeneous phenotypes. Comprehensive genetic familial analysis enables personalized care and accurate genetic counselling, particularly when multiple diagnoses coexist. A family history should not preclude molecular testing, since similar phenotypes can result from different genetic causes.

Acroscyphodysplasia (ASD) is an ultra-rare skeletal dysplasia characterized by severe brachydactyly, metaphyseal scaphoid knee deformities, growth retardation, and intellectual disability. To date, only seven cases of ASD have been reported, all associated with missense variants in the PDE4D gene. We report a 7-year-old girl with ASD features, including midface hypoplasia, severe growth retardation (-4.81 Shwachman-Diamond syndrome (SDS) height), progressive postnatal development of "cup-shaped" knee metaphyses, and unilateral humeral bowing, demonstrating mosaic growth plate involvement. Whole-genome sequencing revealed a novel PDE4D missense variant (c.934C>T, p. Leu312Phe) in the upstream conserved region 2 (UCR2) autoinhibitory domain, which is distinct from known acrodysostosis-associated variants. Expanding the clinical and radiological characteristics, as well as the mutation spectrum of PDE4D-related ASD, is crucial for understanding syndrome variability, aiding in earlier detection, and improving recurrence risk assessment.

Protein kinase A (PKA) is essential in converting extracellular signals into tightly regulated cellular responses controlling vital processes such as growth, development, and gene expression. Activation of PKA is controlled by the binding of cAMP to the regulatory subunit of PKA (R). Several mutations in the ubiquitous RIα isoform of R cause Acrodysostosis 1 (ACRO), a disease characterized by resistance to thyroid-stimulating and parathyroid hormones leading to severe congenital malformations. This work examines the recurrent R366X truncation ACRO mutant, which exhibits severe PKA hypoactivation due to loss of sensitivity to cAMP and the impairment of allosteric networks. The R366X RIα mutant has been previously studied via X-ray crystallography, but the crystal structure only captured the inhibited state and showed minimal difference from the wild type structure. Additionally, previous studies only examined the effects of ACRO mutants on the activation cycle of PKA (i.e. sensitivity to cAMP binding). Here we focus on the less understood signal termination cycle. We hypothesize that R366X acts by perturbing dynamic intermediates relevant to the PKA deactivation cycle, which are not fully recapitulated by static structures. To test our hypothesis, we combined low- and high-resolution approaches for probing protein-ligand binging, mutant stability, and identifying regions exhibiting aberrant allosteric behaviors. Based on our results, we propose a novel mechanism whereby R366X not only impairs physiological PKA activation but also accelerates PKA deactivation by increasing the rate of phosphodiesterase-catalyzed cAMP hydrolysis to 5'-AMP. Our studies shed new light on the current understanding of PKA dysregulation and ACRO's molecular etiology, outlining a multi-resolution experimental design which is transferable to other ACRO mutants.

Miller syndrome is an extremely rare condition in the group of facial dysostosis syndromes. These syndromes have great phenotypic overlap and variability, even within families. To facilitate the differentiation of Miller syndrome from related facial dysostosis syndromes, such as Treacher Collins and Nager syndrome, this study aims to provide an overview of the phenotypic spectrum of the syndrome. A systematic literature search of Embase, MEDLINE/PubMed, Web of Science, and CINAHL was conducted until November 2024. Case reports and case series of patients with a clinical or genetic diagnosis of Miller syndrome in all languages were included. The quality of the included reports was assessed using the Joanna Briggs Institute critical appraisal tool and the Fichas de Lectura Critica 3.0 web application. In total, 44 cases of Miller syndrome were found, with only 18.2% having genetic confirmation. Craniofacial anomalies were prominent, including midface hypoplasia (72.7%) and micrognathia (75.0%), orofacial clefts (77.3%), eyelid anomalies (70.5%), and external ear anomalies (63.6%). Limb anomalies were present in all cases, primarily involving the hands (95.5%), forearms (52.3%), and feet (90.9%). Anomalies in other extracraniofacial tracts were also reported. Despite limitations, including limited genetic confirmation and reliance on literature, this study provides valuable insights into the phenotypic spectrum of Miller syndrome. Efforts for genetic confirmation, international collaboration, and comprehensive reporting are essential to advance research and care for rare conditions like Miller syndrome. Therefore, a detailed checklist for phenotypic evaluation in Miller syndrome cases is provided in this study.

Acrodysostosis (ADO) is a rare form of peripheral dysostosis characterized by skeletal malformations, growth delays, short stature, and distinctive facial features caused by in part by underdeveloped (hypoplasia) of facial bones. Skeletal dysplasia is specific and includes disproportional short stature with short extremities and brachydactyly, multiple cone-shaped epiphyses, scoliosis or kyphosis with spinal stenosis, and advanced bone maturation. Herein, we are highlighting a case that presented with clinical features such as brachydactyly, delayed milestone, growth delay, muscle weakness and nasal hypoplasia. Patient genetic testing was in line with the diagnosis of acrodysostosis. The clinic-radiological correlation was also suggestive of the rare diagnosis of ADO.