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.

A novel variant in the PDE4D gene is the cause of Acrodysostosis type 2 in a Lithuanian patient: a case report.

BACKGROUND: Acrodysostosis is a rare hereditary disorder described as a primary bone dysplasia with or without hormonal resistance. Pathogenic variants in the PRKAR1A and PDE4D genes are known genetic causes of this condition. The latter gene variants are more frequently identified in patients with midfacial and nasal hypoplasia and neurological involvement. The aim of our study was to analyse and confirm a genetic cause of acrodysostosis in a male patient. CASE PRESENTATION: We report on a 29-year-old Lithuanian man diagnosed with acrodysostosis type 2. The characteristic phenotype includes specific skeletal abnormalities, facial dysostosis, mild intellectual disability and metabolic syndrome. Using patient's DNA extracted from peripheral blood sample, the novel, likely pathogenic, heterozygous de novo variant NM_001104631.2:c.581G > C was identified in the gene PDE4D via Sanger sequencing. This variant causes amino acid change (NP_001098101.1:p.(Arg194Pro)) in the functionally relevant upstream conserved region 1 domain of PDE4D. CONCLUSIONS: This report further expands the knowledge of the consequences of missense variants in PDE4D that affect the upstream conserved region 1 regulatory domain and indicates that pathogenic variants of the gene PDE4D play an important role in the pathogenesis mechanism of acrodysostosis type 2 without significant hormonal resistance.

Sleep-disordered breathing and its management in children with rare skeletal dysplasias.

Sleep-disordered breathing (SDB) is common in patients with skeletal dysplasias. The aim of our study was to analyze SDB and respiratory management in children with rare skeletal dysplasias. We performed a retrospective analysis of patients with spondyloepiphyseal dysplasia congenita (SEDC), metatropic dysplasia (MD), spondyloepimetaphyseal dysplasia (SEMD), acrodysostosis (ADO), geleophysic dysplasia (GD), acromicric dysplasia (AD), and spondylocostal dysplasia (SCD) between April 2014 and October 2020. Polygraphic data, clinical management, and patients' outcome were analyzed. Thirty-one patients were included (8 SEDC, 3 MD, 4 SEMD, 1 ADO, 4 GD, 3 AD, and 8 SCD). Sixteen patients had obstructive sleep apnea (OSA): 11 patients (2 with SEDC, 1 with SEMD, 1 with ADO, 1 with GD, 2 with AD, and 4 with SCD) had mild OSA, 2 (1 SEMD and 1 GD) had moderate OSA, and 3 (1 SEDC, 1 MD, 1 SEMD) had severe OSA. Adenotonsillectomy was performed in one patient with SCD and mild OSA, and at a later age in two other patients with ADO and AD. The two patients with moderate OSA were treated with noninvasive ventilation (NIV) because of nocturnal hypoxemia. The three patients with severe OSA were treated with adenotonsillectomy (1 SEDC), adeno-turbinectomy and continuous positive airway pressure (CPAP; 1 MD), and with NIV (1 SEMD) because of nocturnal hypoventilation. OSA and/or alveolar hypoventilation is common in patients with skeletal dysplasias, underlining the importance of systematic screening for SDB. CPAP and NIV are effective treatments for OSA and nocturnal hypoventilation/hypoxemia.

Spondylocostal Dysostosis Associated with Split Spinal Cord and Other Malformations.

Spondylocostal dysostosis is a very rare combination of complex vertebra and rib malformations, accompanied occasionally by other disorders. A 3-year-old girl presented kyphoscoliosis, foot deformities, gate disturbance, and urinary incontinence. The CT and MRI examination revealed kyphosis and scoliosis with a double curve, some absent, broadened, bifurcating and fused ribs, hemivertebrae, butterfly and cleft vertebrae in thoracic and lumbar region, sporadic cleft or absent vertebral arches or pedicles, and hypoplastic sacrum with a cleft of the S2 vertebra. Spina bifida occulta extended from T10 to T11, and from L3 to the end of the sacrum. Two hemicords, separated by a bony septum and surrounded by their own dural tubes (type I), were present from the level of T9 to the conus medullaris. Filum terminale was thick and duplicated. Syringomyelia was present in the thoracic cord from T5 to T8. Finally, a small meningocele was seen at the T10-T11 level, and a subcutaneous lipoma in the thoracolumbar region. To our knowledge, such a combination of vertebra, rib, and cord malformations, including the mentioned additional disorders, has never been reported.

Diaphanospondylodysostosis: Refining the prenatal diagnosis of a rare skeletal disorder.

Diaphanospondylodysostosis (DSD) is a rare autosomal recessive skeletal disorder, characterized mainly by ossification defects in vertebrae, thorax malformations, renal cystic dysplasia and usually death in the perinatal period. DSD is caused by mutations in the bone morphogenetic protein-binding endothelial regulator (BMPER) gene. We describe the prenatal findings of a non-consanguineous Jewish couple (shared Balkan origin), with three affected fetuses that presented with malformations in the spine and chest, reduced ossification of the skull and spine, horseshoe kidney and increased nuchal translucency. The unique combination of these ultrasound (US) features raised the possibility of DSD, which was confirmed by whole exome sequencing (WES) performed on a single fetal DNA and familial segregation. In the three fetuses, a novel homozygous mutation in BMPER (c.410T > A; p.Val137Asp) was found. This mutation, which segregated in the family, was not found in 65 controls of Jewish Balkan origin, and in several large databases. Taken together, the combination of a detailed prenatal US examination and WES may be highly effective in confirming the diagnosis of a rare genetic disease, in this case DSD.

Neonatal umbilical cord blood transplantation halts skeletal disease progression in the murine model of MPS-I.

Umbilical cord blood (UCB) is a promising source of stem cells to use in early haematopoietic stem cell transplantation (HSCT) approaches for several genetic diseases that can be diagnosed at birth. Mucopolysaccharidosis type I (MPS-I) is a progressive multi-system disorder caused by deficiency of lysosomal enzyme α-L-iduronidase, and patients treated with allogeneic HSCT at the onset have improved outcome, suggesting to administer such therapy as early as possible. Given that the best characterized MPS-I murine model is an immunocompetent mouse, we here developed a transplantation system based on murine UCB. With the final aim of testing the therapeutic efficacy of UCB in MPS-I mice transplanted at birth, we first defined the features of murine UCB cells and demonstrated that they are capable of multi-lineage haematopoietic repopulation of myeloablated adult mice similarly to bone marrow cells. We then assessed the effectiveness of murine UCB cells transplantation in busulfan-conditioned newborn MPS-I mice. Twenty weeks after treatment, iduronidase activity was increased in visceral organs of MPS-I animals, glycosaminoglycans storage was reduced, and skeletal phenotype was ameliorated. This study explores a potential therapy for MPS-I at a very early stage in life and represents a novel model to test UCB-based transplantation approaches for various diseases.

Two cases of Legg-Perthes and intellectual disability in Tricho-Rhino-Phalangeal syndrome type 1 associated with novel TRPS1 mutations.

Tricho-Rhino-Phalangeal syndrome is a rare autosomal dominant genetic disorder caused by mutations in the TRPS1 gene. This malformation syndrome is characterized by distinctive craniofacial features including sparse scalp hair, bulbous tip of the nose, long flat philtrum, thin upper vermilion border, and protruding ears. Skeletal abnormalities include cone-shaped epiphyses at the phalanges, hip malformations, and short stature. In this report, we describe two patients with the physical manifestations and genotype of TRPS type I but with learning/intellectual disability not typically described as part of the syndrome. The first patient has a novel heterozygous two-base-pair deletion of nucleotides at 3198-3199 (c.3198-3199delAT) in the TRPS1 gene causing a translational frameshift and subsequent alternate stop codon. The second patient has a 3.08 million base-pair interstitial deletion at 8q23.3 (113,735,487-116,818,578), which includes the TRPS1 gene and CSMD3. Our patients have characteristic craniofacial features, Legg-Perthes syndrome, various skeletal abnormalities including cone shaped epiphyses, anxiety (first patient), and intellectual disability, presenting unusual phenotypes that add to the clinical spectrum of the disease.

Knock-In of the Recurrent R368X Mutation of PRKAR1A that Represses cAMP-Dependent Protein Kinase A Activation: A Model of Type 1 Acrodysostosis.

In humans, activating mutations in the PRKAR1A gene cause acrodysostosis 1 (ACRDYS1). These mutations result in a reduction in PKA activation caused by an impaired ability of cAMP to dissociate mutant PRKAR1A from catalytic PKA subunits. Two striking features of this rare developmental disease are renal resistance to PTH and chondrodysplasia resulting from the constitutive inhibition of PTHR1/Gsa/AC/cAMP/PKA signaling. We developed a knock-in of the recurrent ACRDYS1 R368X PRKAR1A mutation in the mouse. No litters were obtained from [R368X]/[+] females (thus no homozygous [R368X]/[R368X] mice). In [R368X]/[+] mice, Western blot analysis confirmed mutant allele heterozygous expression. Growth retardation, peripheral acrodysostosis (including brachydactyly affecting all digits), and facial dysostosis were shown in [R368X]/[+] mice by weight curves and skeletal measurements (µCT scan) as a function of time. [R368X]/[+] male and female mice were similarly affected. Unexpected, however, whole-mount skeletal preparations revealed a striking delay in mineralization in newborn mutant mice, accompanied by a decrease in the height of terminal hypertrophic chondrocyte layer, an increase in the height of columnar proliferative prehypertrophic chondrocyte layer, and changes in the number and spatial arrangement of proliferating cell nuclear antigen (PCNA)-positive chondrocytes. Plasma PTH and basal urinary cAMP were significantly higher in [R368X]/[+] compared to WT mice. PTH injection increased urinary cAMP similarly in [R368X]/[+] and WT mice. PRKACA expression was regulated in a tissue (kidney not bone and liver) manner. This model, the first describing the germline expression of a PRKAR1A mutation causing dominant repression of cAMP-dependent PKA, reproduced the main features of ACRDYS1 in humans. It should help decipher the specificity of the cAMP/PKA signaling pathway, crucial for numerous stimuli. In addition, our results indicate that PRKAR1A, by tempering intracellular cAMP levels, is a molecular switch at the crossroads of signaling pathways regulating chondrocyte proliferation and differentiation. © 2016 American Society for Bone and Mineral Research.

Congenital Spondylolytic Spondylolisthesis of C2 Vertebra Associated With Atlanto-Axial Dislocation, Chiari Type I Malformation, and Anomalous Vertebral Artery: Case Report With Review Literature.

BACKGROUND: Congenital spondylolytic spondylolisthesis of C2 vertebra resulting from deficient posterior element of the axis is rarely described in the literature. CASE DESCRIPTION: We describe a unique case of agenesis of posterior elements of C2 with craniovertebral junction anomalies consisting of osseous, vascular, and soft tissue anomalies. A 26-year-old man presented with symptoms of upper cervical myelopathy of 12 months' duration. A computed tomography scan of the cervical spine including the craniovertebral junction revealed spondylolisthesis of C2 over C3, atlantoaxial dislocation, occipitalization of the atlas, hypoplasia of the odontoid, and cleft posterior C1 arch. Additionally, the axis vertebra was found devoid of its posterior elements except bilaterally rudimentary pedicles. Magnetic resonance imaging revealed tonsilar herniation, suggesting associated Chiari type I malformation. CT angiogram of the vertebral arteries displayed persistent bilateral first intersegmental arteries crossing the posterior aspect of the C1/2 facet joint. This patient underwent foramen magnum decompression, C3 laminectomy with occipito-C3/C4 posterior fusion using screw and rod to maintain the cervical alignment and stability. CONCLUSION: We report this rare constellation of congenital craniovertebral junction anomaly and review the relevant literature.

Multiple cervical hemivertebra resection and staged thoracic pedicle subtraction osteotomy in the treatment of complicated congenital scoliosis.

PURPOSE: To present our experience of staged correction with multiple cervical hemivertebra resection and thoracic pedicle subtraction osteotomy (PSO) treating a rare and complicated congenital scoliosis. METHODS: A 14-year-old male presented with progressive torticollis and spine deformity. The malformation developed since birth, and back pain after long-time sitting or exercise arose since 6 months before, which was unsuccessfully treated by physiotherapy. X-ray showed a right cervical curve of 60° and a left compensatory thoracic curve of 90°. Three-dimensional computed tomography (3-D CT) scan revealed three semi-segmented hemivertebrae (C4, C5 and C6) on the right side. Based on our staged strategy, the three consecutive cervical hemivertebrae, as the major pathology causing the deformity, were firstly resected by the combined posterior and anterior approach. Six months later, T6 PSO osteotomy was used to correct the structural compensatory thoracic curve. RESULTS: The cervical curve was reduced to 23° while the thoracic curve to 60° after the first-stage surgery, and the thoracic curve was further reduced to 30° after the second-stage surgery. The radiograph at 5-year follow-up showed that both the coronal and sagittal balance were well restored and stabilized, with the occipital tilt reduced from 12° to 0°. CONCLUSIONS: Our strategy may provide an option for similar cases with multiple consecutive cervical hemivertebrae and a large structural compensatory thoracic curve, which proved to achieve excellent correction in both the coronal and sagittal planes with acceptable neurologic risk.

Cervical subluxation associated with posterior cervical hemivertebra.

PURPOSE: Hemivertebrae, associated with a failure in the formation and fusion of vertebral body ossification nuclei, are a common cause of thoracic or lumbar scoliosis. A cervical location is rare and even rarer as a cause of cervical subluxation in flexion and extension (for which only one previous case has been found). CASE REPORT: We report on the case of a 7-year-old female patient, who was examined for a cervical fusion defect, consisting of a posterior C4 hemivertebra and a left hemiblock from C5 to C7. After performing surgery consisting of a C4 corpectomy and anterior fixation with intersomatic graft and plate, adequate cervical stabilization with only a self-limiting left C6 brachialgia and ipsilateral Horner syndrome occurs in the postoperative period. CONCLUSION: Posterior cervical hemivertebra associated with instability is a very rare finding. The anterior approach with corpectomy and anterior plate enables suitable stabilization.

Expanding the phenotype of spondylospinal thoracic dysostosis (the Turkel-Chen-Johnson syndrome).

Spondylospinal thoracic dysostosis can be considered a type of spondylocostal dysostosis because of the occurrence of vertebral defects (hemivertebrae and vertebral body fusion) and thoracic anomalies (short thorax and pulmonary hypoplasia). This syndrome was described by Johnson et al. (1997) in two siblings with dwarfism, short thorax, curved spine, fusion of the vertebrae and spinal process, multiple pterygium, and arthrogryposis. We describe the case of a 16-year-old Mexican girl with the longest survival recorded (the previous oldest patient was 7 years old) and analyze the natural history and describe some new features of this rare entity.

Fetal skeletal computed tomography: when? How? Why?

PURPOSE: To study the additional role of fetal skeletal computed tomography in suspected prenatal bone abnormalities. MATERIALS AND METHODS: Two centers included in a retrospective study all fetuses who benefited from skeletal computed tomography for a suspected constitutional bone disease or focal dysostosis. RESULTS: A total of 198 patients were included. CT was performed in 112 patients (56%) for an isolated short femur below the third percentile (group A), in 15 patients (8%) for bowed or fractured femur (group B), in 23 patients (12%) for biometric discrepancy between a short femur and increased head circumference (group C) and in 48 patients (24%) for suspected focal dysostosis (group D). CT was interpreted as normal in 126 cases (64%), i.e. 87% in group A, 0% in group B, 65% in group C and 25% in group D. When including only cases with postnatal or postmortem clinical and/or radiological confirmation was available, CT provided additional and/or more accurate information than ultrasound in 20% of cases in group A, 66% in group B, 30% in group C and 72% in group D. Sixty-seven percent of patients in whom CT was interpreted as normal were lost to follow-up. CONCLUSION: In isolated short femur, fetal skeletal CT is normal in the great majority of cases although protocolized follow-up of these babies is absolutely compulsory, as a large proportion is lost to follow-up. Fetal skeletal CT can confirm or improve imaging for the suspected diagnosis in suspected focal dysostosis or constitutional bone disease.

Molecular evaluation of a novel missense mutation & an insertional truncating mutation in SUMF1 gene.

BACKGROUND & OBJECTIVES: Multiple suphphatase deficiency (MSD) is an autosomal recessive disorder affecting the post translational activation of all enzymes of the sulphatase family. To date, approximately 30 different mutations have been identified in the causative gene, sulfatase modifying factor 1 (SUMF1). We describe here the mutation analysis of a case of MSD. METHODS: The proband was a four year old boy with developmental delay followed by neuroregression. He had coarse facies, appendicular hypertonia, truncal ataxia and ichthyosis limited to both lower limbs. Radiographs showed dysostosis multiplex. Clinical suspicion of MSD was confirmed by enzyme analysis of four enzymes of the sulphatase group. RESULTS: The patient was compound heterozygote for a c.451A>G (p.K151E) substitution in exon 3 and a single base insertion mutation (c.690_691 InsT) in exon 5 in the SUMF1 gene. The bioinformatic analysis of the missense mutation revealed no apparent effect on the overall structure. However, the mutated 151-amino acid residue was found to be adjacent to the substrate binding and the active site residues, thereby affecting the substrate binding and/or catalytic activity, resulting in almost complete loss of enzyme function. CONCLUSIONS: The two mutations identified in the present case were novel. This is perhaps the first report of an insertion mutation in SUMF1 causing premature truncation of the protein.

Heterozygous mutations in cyclic AMP phosphodiesterase-4D (PDE4D) and protein kinase A (PKA) provide new insights into the molecular pathology of acrodysostosis.

Acrodysostosis without hormone resistance is a rare skeletal disorder characterized by brachydactyly, nasal hypoplasia, mental retardation and occasionally developmental delay. Recently, loss-of-function mutations in the gene encoding cAMP-hydrolyzing phosphodiesterase-4D (PDE4D) have been reported to cause this rare condition but the pathomechanism has not been fully elucidated. To understand the pathogenetic mechanism of PDE4D mutations, we conducted 3D modeling studies to predict changes in the binding efficacy of cAMP to the catalytic pocket in PDE4D mutants. Our results indicated diminished enzyme activity in the two mutants we analyzed (Gly673Asp and Ile678Thr; based on PDE4D4 residue numbering). Ectopic expression of PDE4D mutants in HEK293 cells demonstrated this reduction in activity, which was identified by increased cAMP levels. However, the cells from an acrodysostosis patient showed low cAMP accumulation, which resulted in a decrease in the phosphorylated cAMP Response Element-Binding Protein (pCREB)/CREB ratio. The reason for this discrepancy was due to a compensatory increase in expression levels of PDE4A and PDE4B isoforms, which accounted for the paradoxical decrease in cAMP levels in the patient cells expressing mutant isoforms with a lowered PDE4D activity. Skeletal radiographs of 10-week-old knockout (KO) rats showed that the distal part of the forelimb was shorter than in wild-type (WT) rats and that all the metacarpals and phalanges were also shorter in KO, as the name acrodysostosis implies. Like the G-protein α-stimulatory subunit and PRKAR1A, PDE4D critically regulates the cAMP signal transduction pathway and influences bone formation in a way that activity-compromising PDE4D mutations can result in skeletal dysplasia. We propose that specific inhibitory PDE4D mutations can lead to the molecular pathology of acrodysostosis without hormone resistance but that the pathological phenotype may well be dependent on an over-compensatory induction of other PDE4 isoforms that can be expected to be targeted to different signaling complexes and exert distinct effects on compartmentalized cAMP signaling.

Fryns syndrome with vertebral defects: a novel association in a Mexican infant.

We report a Mexican mestizo 2 months old male with Fryns syndrome and vertebral defects. The patient's phenotype included typical craniofacial dysmorphism, short neck, agenesis of the corpus callosum, congenital left diaphragmatic hernia, complex heart disease, C1 to C6 vertebral agenesis with increased interpedicular space, thoracic rotoscoliosis, broad medial ends of the clavicles, brachytelephalangy of hands and feet with fingers axially deviated, and nail hypoplasia. Renal and chromosomal evaluations were normal. Since this is the first description of cervical vertebrae agenesis and thoracic rotoscoliosis in Fryns syndrome, we propose that these clinical and radiological features should be incorporated to the Fryns syndrome phenotype and specifically looked for in other children.