Severe cardiac anomalies in sibs with Larsen syndrome

Clinical diagnosis of Larsen syndrome, Stickler syndrome and Loeys-Dietz syndrome in a 19-year old male: a case report

Background

Larsen syndrome is a hereditary disorder characterized by osteochondrodysplasia, congenital large-joint dislocations, and craniofacial abnormalities. The autosomal dominant type is caused by mutations in the gene that encodes the connective tissue protein, filamin B (FLNB). Loeys-Dietz syndrome (LDS) is an autosomal dominant connective tissue disorder characterized by arterial aneurysms, dissections and tortuosity, and skeletal, including craniofacial, manifestations. Mutations in five genes involved in the transforming growth factor beta (TGF-β) signaling pathway cause five types of LDS. Stickler syndrome is a genetically heterogeneous arthro-ophthalmopathy caused by defects in collagen, exhibiting a wide specter of manifestations in connective tissue. A rare case is reported that was diagnosed with all these three hereditary connective tissue disorders.

Case presentation

A 19 year-old, Norwegian male with a clinical diagnosis of Larsen syndrome and with healthy, non-consanguineous parents attended a reference center for rare connective tissue disorders. Findings at birth were hypotonia, joint hypermobility, hyperextended knees, adductovarus of the feet, cervical kyphosis, craniofacial abnormalities, and an umbilical hernia. From toddlerhood, he required a hearing aid due to combined conductive and sensorineural hearing loss. Eye examination revealed hyperopia, astigmatism, and exotropia. At 10 years of age, he underwent emergency surgery for rupture of an ascending aortic aneurysm. At 19 years of age, a diagnostic re-evaluation was prompted by the findings of more distal aortic dilation, tortuosity of precerebral arteries, and skeletal findings. High throughput sequencing of 34 genes for hereditary connective tissue disorders did not identify any mutation in FLNB, but did identify a de novo missense mutation in TGFBR2 and a nonsense mutation in COL2A1 that was also present in his unaffected father. The diagnosis was revised to LDS Type 2. The patient also fulfills the proposed criteria for Stickler syndrome with bifid uvula, hearing loss, and a known mutation in COL2A1.

Conclusion

LDS should be considered in patients with a clinical diagnosis of Larsen syndrome, in particular in the presence of arterial aneurysms or tortuosity. Due to genetic heterogeneity and extensive overlap of clinical manifestations, genetic high throughput sequencing analysis is particularly useful for the differential diagnosis of hereditary connective tissue disorders.

GZF1 Mutations Expand the Genetic Heterogeneity of Larsen Syndrome

Larsen syndrome is characterized by the dislocation of large joints and other less consistent clinical findings. Heterozygous FLNB mutations account for the majority of Larsen syndrome cases, but biallelic mutations in CHST3 and B4GALT7 have been more recently described, thus confirming the existence of recessive forms of the disease. In a multiplex consanguineous Saudi family affected by severe and recurrent large joint dislocation and severe myopia, we identified a homozygous truncating variant in GZF1 through a combined autozygome and exome approach. Independently, the same approach identified a second homozygous truncating GZF1 variant in another multiplex consanguineous family affected by severe myopia, retinal detachment, and milder skeletal involvement. GZF1 encodes GDNF-inducible zinc finger protein 1, a transcription factor of unknown developmental function, which we found to be expressed in the eyes and limbs of developing mice. Global transcriptional profiling of cells from affected individuals revealed a shared pattern of gene dysregulation and significant enrichment of genes encoding matrix proteins, including P3H2, which hints at a potential disease mechanism. Our results suggest that GZF1 mutations cause a phenotype of severe myopia and significant articular involvement not previously described in Larsen syndrome.

Larsen Syndrome

Larsen syndrome is a rare inherited disorder of collagen formation with multiple joint dislocations, cardiac abnormalities, short stature, talipes equinovarus, short and broad fingertips, spatula-like thumbs, supernumerary ossification center in the calcaneus, hearing loss, neurologic impairment, cryptorchidism, and characteristic craniofacial abnormalities. The sonographic prenatal findings in a case of Larsen syndrome at 26 weeks’ gestation, which demonstrated joint dislocations, hypertelorism, frontal bossing, micrognathia, and upper and lower limb shortening and confirmed at both 29 and 30 weeks’ gestation, are presented and discussed. When evaluating patients with a positive family history of Larsen syndrome, sonographers should carefully scan and meticulously assess the fetal extremities for signs of dislocation and the face for signs of flat features, hypertelorism, micrognathia, and depressed nasal bridge, distinctive features of the syndrome.

Aneurysm of the ductus arteriosus in a patient with Larsen syndrome

Larsen syndrome is characterized by multiple congenital joint dislocations and a characteristic flattened facial appearance. The aetiology is unknown, but the syndrome is considered a probable connective tissue disorder and the cardiovascular manifestations are similar to those of Marfan syndrome. We describe an 8-year-old girl with the characteristic features of Larsen syndrome who was also affected by a saccular aneurysm of the descending aorta, just distal to the left subclavian artery. We present the radiological findings and review the literature.

A molecular and clinical study of Larsen syndrome caused by mutations in FLNB

BACKGROUND

Larsen syndrome is an autosomal dominant osteochondrodysplasia characterised by large-joint dislocations and craniofacial anomalies. Recently, Larsen syndrome was shown to be caused by missense mutations or small inframe deletions in FLNB, encoding the cytoskeletal protein filamin B. To further delineate the molecular causes of Larsen syndrome, 20 probands with Larsen syndrome together with their affected relatives were evaluated for mutations in FLNB and their phenotypes studied.

METHODS

Probands were screened for mutations in FLNB using a combination of denaturing high-performance liquid chromatography, direct sequencing and restriction endonuclease digestion. Clinical and radiographical features of the patients were evaluated.

RESULTS AND DISCUSSION

The clinical signs most frequently associated with a FLNB mutation are the presence of supernumerary carpal and tarsal bones and short, broad, spatulate distal phalanges, particularly of the thumb. All individuals with Larsen syndrome-associated FLNB mutations are heterozygous for either missense or small inframe deletions. Three mutations are recurrent, with one mutation, 5071G-->A, observed in 6 of 20 subjects. The distribution of mutations within the FLNB gene is non-random, with clusters of mutations leading to substitutions in the actin-binding domain and filamin repeats 13-17 being the most common cause of Larsen syndrome. These findings collectively define autosomal dominant Larsen syndrome and demonstrate clustering of causative mutations in FLNB.

General anaesthesia in a child with Larsen syndrome

Larsen syndrome is a rare congenital connective tissue disorder which is characterized by multiple dislocations of major joints, typical facial appearance, cervical spine narrowing and instability and respiratory difficulties secondary to laryngotracheomalacia. A case of general anaesthesia for laparoscopic hernia repair in a male child aged 16 months with this syndrome is presented. Anaesthesia was well tolerated though intubation proved difficult. Cervical spine instability and postoperative respiratory complications are potential problems.

Thoracolumbar kyphoscoliosis in Larsen's syndrome. A case report

Severe thoracolumbar kyphosis in Larsen's syndrome is rare. A successful 10-year treatment course, including T2-L4 subfascial rod placement when the patient was 6 years 3 months of age, nine periodic lengthenings, and definitive surgery at age 14 years 4 months is presented. From preoperative to 2-year postoperative definitive surgery, the patient's T1 to S1 spine length increased from 19 to 36 cm. The patient's 83 degrees thoracolumbar kyphosis was transformed to 45 degrees kyphosis and 28 degrees lumbar lordosis, and scolioses of 95 degrees and 65 degrees were reduced to 64 degrees and 50 degrees.

Anesthetic implications of Larsen syndrome

In this article I present two children with Larsen syndrome who required anesthetic care during surgical procedures of the ear-nose-throat (ENT) region. The anesthetic implications of this disorder are discussed. Larsen syndrome consists of multiple joint dislocations and a characteristic facies. Associated orthopedic abnormalities include cervical spine vertebral body hypoplasia and hemivertebrae, which may lead to cervical kyphosis and compromise of cervical cord function. Of prime importance to the anesthesiologist are the associated defects of the airway including laryngotracheomalacia, which may predispose the patient to perioperative respiratory compromise. Associated cardiac defects have also been described including atrial and ventricular septal defects.

Brain dysplasia associated with Larsen-like syndrome

We present an autopsy case of Larsen-like syndrome with unusually severe neurologic complications. The patient, a 3-year-old girl, manifested severe psychomotor retardation, tetraplegia, and intractable partial seizures as well as multiple joint dislocations with other skeletal deformities, minor external anomalies, and laryngotracheomalacia. Neuropathological examination of the brain revealed (1) cortical dysgenesis in the bilateral perisylvian region; (2) protrusions of the brain parenchyma into the subarachnoid space, (3) abnormal arrangement of olivary neurons, (4) dilation of the lateral ventricles with subventricular gliosis and multiple glial nodules, (5) hypoplasia of the cerebral white matter with subcortical astrocytosis, and (6) necrotic change in Sommer sector of the hippocampus. There were no microscopic abnormalities in the mesenchymal tissue of the brain (i.e., vascular walls and the meninges). Cortical dysgenesis in the perisylvian region was characterized by a zonal heterotopia of pyramidal and granule neurons in the molecular layer, which clinically may be closely related to intractable partial seizures in the orofacial area. Findings 1, 2, and 3 may represent a disturbance of neuroblast migration, speculated to have occurred during the latest stage of migration (around 20-25 weeks gestation). There are few published reports describing the combination of Larsen-like syndrome and brain dysplasia. Correlation of brain dysplasia with congenital skeletal abnormalities is unclear in our patient. We speculate that systemic hypoxic-ischemic insults during the second half of gestation and/or some genetic factors might be possible causes of brain dysplasia.

Linkage studies of four fibrillar collagen genes in three pedigrees with Larsen-like syndrome

We report seven children from three families who had a set of common clinical features suggestive of Larsen-like syndrome, including unusual facies, bilateral dislocations of the knees and elbows, club foot, and short stature. All of the patients originated from the island of La Réunion in the Indian Ocean. The occurrence of several affected sibs in these families and the large number of consanguineous marriages on this island are consistent with autosomal recessive inheritance of the disease. Based on this hypothesis, the pedigrees were used for linkage analysis in a candidate gene assay. Lod score calculations in a pairwise study with four different fibrillar collagen genes, COL1A1, COL1A2, COL3A1, and COL5A2, allowed us to exclude these genes as the mutant loci. Supporting this, electrophoretic analysis of collagens derived from fibroblast cultures failed to show defective molecules. We conclude that this syndrome is not a collagen disorder.