Integrative analysis of Lunatic Fringe variants associated with spondylocostal dysostosis type-III.

Lunatic Fringe (LFNG) is required for spinal development. Biallelic pathogenic variants cause spondylocostal dysostosis type-III (SCD3), a rare disease generally characterized by malformed, asymmetrical, and attenuated development of the vertebral column and ribs. However, a variety of SCD3 cases reported have presented with additional features such as auditory alterations and digit abnormalities. There has yet to be a single, comprehensive, functional evaluation of causative LFNG variants and such analyses could unveil molecular mechanisms for phenotypic variability in SCD3. Therefore, nine LFNG missense variants associated with SCD3, c.564C>A, c.583T>C, c.842C>A, c.467T>G, c.856C>T, c.601G>A, c.446C>T, c.521G>A, and c.766G>A, were assessed in vitro for subcellular localization and protein processing. Glycosyltransferase activity was quantified for the first time in the c.583T>C, c.842C>A, and c.446C>T variants. Primarily, our results are the first to satisfy American College of Medical Genetics and Genomics PS3 criteria (functional evidence via well-established assay) for the pathogenicity of c.583T>C, c.842C>A, and c.446C>T, and replicate this evidence for the remaining six variants. Secondly, this work indicates that all variants that prevent Golgi localization also lead to impaired protein processing. It appears that the FRINGE domain is responsible for this phenomenon. Thirdly, our data suggests that variant proximity to the catalytic residue may influence whether LFNG is improperly trafficked and/or enzymatically dysfunctional. Finally, the phenotype of the axial skeleton, but not elsewhere, may be modulated in a variant-specific fashion. More reports are needed to continue testing this hypothesis. We anticipate our data will be used as a basis for discussion of genotype-phenotype correlations in SCD3.

A rare skeletal dysplasia in the etiology of severe scoliosis: Diaphanospondylodysostosis.

Diaphanospondylodysostosis is a rare genetic skeletal disorder caused by biallelic variants in the BMPER gene. The term, diaphanospondylodysostosis, includes ischiospinal dysotosis, which was previously known as a distinct entity with milder clinical features. The clinical phenotype of diaphanospondylodysostosis is quite variable with mortality in early postnatal life in some patients. Main clinical and radiographic features are narrow thorax, vertebral segmentation defects, rib anomalies, ossification defects of vertebrae, ischium and sacrum, and renal cysts. In this study, we report on a 14-year-old girl patient with diaphanospondylodysostosis harbouring a novel BMPER mutation. The patient presented with severe scoliosis and severely hypoplastic/aplastic distal phalanges of the fingers and toes, findings yet hitherto not described in this syndrome.

Afectación respiratoria en paciente con acrodisostosis: una asociación infrecuente de una enfermedad rara / Respiratory impairment in a patient with acrodysostosis: A rare association of an uncommon pathology

La acrodisostosis es una displasia esquelética rara, de herencia autosómica dominante, que se caracteriza por la presencia de disostosis facial y periférica, talla baja y diferentes grados de obesidad. La acrodisostosis de tipo 1, secundaria a la mutación heterocigota en el gen PRKAR1A (17q24.2), se caracteriza por la asociación de resistencia hormonal múltiple con anomalías esqueléticas. Su incidencia está infradiagnosticada debido a que comparte rasgos clínicos y de laboratorio con otras entidades como el seudohipoparatiroidismo. Presentamos el caso de una niña de 8 años, con acrodisostosis tipo 1, confirmada mediante estudio genético. Además del fenotipo característico descrito, la talla baja y la resistencia hormonal, la paciente presentó una afectación progresiva de la función pulmonar: un patrón pulmonar obstructivo no reversible. En la literatura revisada, no se han encontrado otros casos que describan esta asociación entre acrodisostosis y afectación respiratoria.

Acrodysostosis is a rare skeletal displasia, of autosomal dominant inheritance, characterized by the presence of facial and peripheral dysostosis, short stature and obesity. Type 1 acrodysostosis is secondary to a mutation in the PRKAR1A (17q24.2) gene, which results in multi hormonal resistance and skeletal anomalities. This syndrome is under-diagnosed as it shares analytical and clinical characteristics with other entities, such as pseudohypoparathyroidism. We report the case of an eight-year-old girl with genetically confirmed type 1 acrodysostosis. In addition to the characteristic phenotype described, the short stature and the hormonal resistance, the patient suffered a progressive lung function deterioration: an irreversible pulmonary obstructive pattern. We have not found in previous literature cases reporting an association between acrodysostosis and lung function impairement.