An orthodontic perspective on Larsen syndrome

Background Larsen syndrome (LS) is a rare disorder of osteochondrodysplasia. In addition to large-joint dislocations, craniofacial anomalies are typical characteristics. In this report, we performed orthodontic analyses, including skeletal and occlusal evaluations, to examine whether the craniofacial skeletal morphology leads to the craniofacial anomalies in LS. Case presentation A 5 year old Japanese girl who was clinically diagnosed with LS was referred to the orthodontic clinic in the Fukuoka Dental College Medical and Dental Hospital because of a malocclusion. Clinical findings at birth were knee-joint dislocations, equinovarus foot deformities, and cleft soft palate. The patient showed craniofacial anomalies with hypertelorism, prominent forehead, depressed nasal bridge, and flattened midface. To evaluate the craniofacial skeletal morphology, cephalometric analysis was performed. In the frontal cephalometric analysis, the larger widths between bilateral points of the orbitale were related to hypertelorism. The lateral cephalometric analysis revealed the midface hypoplasia and the retrognathic mandible. These findings were responsible for the flattened appearance of the patient’s face, even if the anteroposterior position of the nasion was normal. Her forehead looked prominent in relation to the face probably because of the retrognathic maxilla and mandible. Both the study model and the frontal cephalometric analysis indicated constriction of the upper and lower dental arches. The posterior crossbite facilitated by the premature contacts had developed in association with the constriction of the upper dental arch. Conclusions This patient had some craniofacial anomalies with characteristic appearances in LS. It was evident that the underlying skeletal morphology led to the craniofacial dysmorphism.

Deciphering the Role of Filamin B Calponin-Homology Domain in Causing the Larsen Syndrome, Boomerang Dysplasia, and Atelosteogenesis Type I Spectrum Disorders via a Computational Approach

Filamins (FLN) are a family of actin-binding proteins involved in regulating the cytoskeleton and signaling phenomenon by developing a network with F-actin and FLN-binding partners. The FLN family comprises three conserved isoforms in mammals: FLNA, FLNB, and FLNC. FLNB is a multidomain monomer protein with domains containing an actin-binding N-terminal domain (ABD 1–242), encompassing two calponin-homology domains (assigned CH1 and CH2). Primary variants in FLNB mostly occur in the domain (CH2) and surrounding the hinge-1 region. The four autosomal dominant disorders that are associated with FLNB variants are Larsen syndrome, atelosteogenesis type I (AOI), atelosteogenesis type III (AOIII), and boomerang dysplasia (BD). Despite the intense clustering of FLNB variants contributing to the LS-AO-BD disorders, the genotype-phenotype correlation is still enigmatic. In silico prediction tools and molecular dynamics simulation (MDS) approaches have offered the potential for variant classification and pathogenicity predictions. We retrieved 285 FLNB missense variants from the UniProt, ClinVar, and HGMD databases in the current study. Of these, five and 39 variants were located in the CH1 and CH2 domains, respectively. These variants were subjected to various pathogenicity and stability prediction tools, evolutionary and conservation analyses, and biophysical and physicochemical properties analyses. Molecular dynamics simulation (MDS) was performed on the three candidate variants in the CH2 domain (W148R, F161C, and L171R) that were predicted to be the most pathogenic. The MDS analysis results showed that these three variants are highly compact compared to the native protein, suggesting that they could affect the protein on the structural and functional levels. The computational approach demonstrates the differences between the FLNB mutants and the wild type in a structural and functional context. Our findings expand our knowledge on the genotype-phenotype correlation in FLNB-related LS-AO-BD disorders on the molecular level, which may pave the way for optimizing drug therapy by integrating precision medicine.

Knee arthrodesis for a congenital luxation with Larsen syndrome

A 31-year-old woman with known Larsen syndrome presented with congenital chronic luxation of her right knee with increasing instability symptoms, which limited her daily activities. We refrained from a constrained knee arthroplasty due to her relatively young age and decided to perform a knee arthrodesis. Knee arthrodesis is a viable lifelong-lasting operative treatment alternative for specific instability-related knee disease. The knee arthrodesis was performed by double plating with an additional fixation of the patella. At 1-yearfollow-up, she was able to walk without limitations and did not experience any pain with complete consolidation of the arthrodesis. At 2-year follow-up, she performed all her daily activities without limitations. Both the Knee injury and Osteoarthritis Outcome Score (KOOS) and the International Knee Documentation Committee subjective knee form (IKDC) improved at 2-year follow-up (KOOS: 61.3; IKDC: 56.3) compared with 1-year follow-up (KOOS: 52; IKDC: 40.2).

Facial, Skeletal and Radiological Features of Larsen Syndrome: A Case Report

Larsen syndrome is a rare congenital osteochondrodysplasia resulting in multiple joint dislocations and typical facial features. The inheritance pattern can be autosomal dominant or recessive, with the recessive pattern being more severe. This condition requires prolonged orthopaedic treatment and achievement of complete normal function is unlikely. The author hereby present a case report of three-year-old female child with this syndrome which was diagnosed by clinical examination and radiological findings.

A 360-Degree Surgical Approach for Correction of Cervical Kyphosis and Atlantoaxial Dislocation in the Case of Larsen Syndrome

Larsen syndrome is chronic debilitating disease that presents with multiple joint dislocations and severely affects the cervical spine in the form of cervical kyphosis and atlantoaxial dislocation. Children usually present in early with a myriad of deficits, compressive myelopathy being the most common. In addition to a bony compression, there is sometimes a soft tissue component, which is seldom addressed. We present here a case of atlantoaxial dislocation with cervical kyphosis due to Larsen syndrome, and along with our previous experience on syndromic atlantoaxial dislocations, we try to define an algorithm for the treatment approach of these onerous challenges. The importance of early intervention is also emphasized with a literature review of similar cases. In addition to the obvious physical damage, early intervention can also avoid the more sinister socioeconomic face of this debilitating disease.