Clinical and ultrastructural findings in three patients with geleophysic dysplasia

Geleophysic dysplasia: novel missense variants and insights into ADAMTSL2 intracellular trafficking

Geleophysic dysplasia (GPHYSD1, MIM231050; GPHYSD2, MIM614185; GPHYSD3, MIM617809) is an autosomal disorder characterized by short-limb dwarfism, brachydactyly, cardiac valvular disease, and laryngotracheal stenosis. Mutations in ADAMTSL2, FBN1, and LTBP3 genes are responsible for this condition. We found that three previously described cases of GPHYSD diagnosed clinically were homozygote or compound heterozygotes for five ADAMTSL2 variants, four of which not being previously reported. By electron microscopy, skin fibroblasts available in one case homozygote for an ADAMTSL2 variant showed a defective intracellular localization of mutant ADAMTSL2 protein that did not accumulate within lysosome-like intra-cytoplasmic inclusions. Moreover, this mutant ADAMTSL2 protein was less secreted in medium and resulted in increased SMAD2 phosphorylation in transfected HEK293 cells.

Limb- and tendon-specific Adamtsl2 deletion identifies a role for ADAMTSL2 in tendon growth in a mouse model for geleophysic dysplasia

Geleophysic dysplasia is a rare, frequently lethal condition characterized by severe short stature with progressive joint contractures, cardiac, pulmonary, and skin anomalies. Geleophysic dysplasia results from dominant fibrillin-1 (FBN1) or recessive ADAMTSL2 mutations, suggesting a functional link between ADAMTSL2 and fibrillin microfibrils. Mice lacking ADAMTSL2 die at birth, which has precluded analysis of postnatal limb development and mechanisms underlying the skeletal anomalies of geleophysic dysplasia. Here, detailed expression analysis of Adamtsl2 using an intragenic lacZ reporter shows strong Adamtsl2 expression in limb tendons. Expression in developing and growing bones is present in regions that are destined to become articular cartilage but is absent in growth plate cartilage. Consistent with strong tendon expression, Adamtsl2 conditional deletion in limb mesenchyme using Prx1-Cre led to tendon anomalies, albeit with normal collagen fibrils, and distal limb shortening, providing a mouse model for geleophysic dysplasia. Unexpectedly, conditional Adamtsl2 deletion using Scx-Cre, a tendon-specific Cre-deleter strain, which does not delete in cartilage, also impaired skeletal growth. Recombinant ADAMTSL2 is shown here to colocalize with fibrillin microfibrils in vitro, and enhanced staining of fibrillin-1 microfibrils was observed in Prx1-Cre Adamtsl2 tendons. The findings show that ADAMTSL2 specifically regulates microfibril assembly in tendons and that proper microfibril composition in tendons is necessary for tendon growth. We speculate that reduced bone growth in geleophysic dysplasia may result from external tethering by short tendons rather than intrinsic growth plate anomalies. Taken together with previous work, we suggest that GD results from abnormal microfibril assembly in tissues, and that ADAMTSL2 may limit the assembly of fibrillin microfibrils.

Geleophysic dysplasia: 48 year clinical update with emphasis on cardiac care

Geleophysic dysplasia is a rare skeletal dysplasia often complicated by progressive cardiac disease. Information about long-term outcomes is limited. A clinical update of the oldest surviving patient described with geleophysic dysplasia type 1 is provided. Special note is made in relation to the cardiac disease and interventions. Genetic testing of ADAMTSL2 revealed a previously reported missense mutation as well as a novel nonsense mutation, which can be added to the list of causative mutations in geleophysic dysplasia.

The Clinical Cases of Geleophysic Dysplasia: One Gene, Different Phenotypes

Background

Geleophysic dysplasia is a rare multisystem disorder that principally affects the bones, joints, heart, and skin. This condition is inherited either in an autosomal dominant pattern due to FBN1 mutations or in an autosomal recessive pattern due to ADAMTSL2 mutations. Two patients with unaffected parents from unrelated families presented to their endocrinologist with severe short stature, resistant to growth hormone treatment. Routine endocrine tests did not reveal an underlying etiology. Exome sequencing was performed in each family. Our two patients, harboring de novo heterozygous FBN1 mutations p.Tyr1696Asp and p.Cys1748Ser, had common clinical symptoms such as severe short stature, characteristic facial features, short hands and feet, and limitation of joint movement. However, one patient had severe cardiac involvement whereas the other patient had tracheal stenosis requiring tracheostomy placement.

Conclusions

Patients with severe dwarfism, skeletal anomalies, and other specific syndromic features (e.g., tracheal stenosis and cardiac valvulopathy) should undergo genetic testing to exclude acromelic dysplasia syndromes.

Clinical Phenotype of Musladin-Lueke Syndrome in 2 Beagles

Musladin-Lueke syndrome (MLS), previously termed Chinese Beagle syndrome, is an autosomal-recessive connective tissue disorder characterized by extensive fibrosis of the skin and joints that was first identified in Beagles in the 1970s. Recent research identified a founder mutation (c.660C>T; p.R221C) in the ADAMTSL2 gene in Beagles with MLS. Here, we report the detailed clinical phenotype and laboratory findings in 2 Beagles affected with MLS. We discuss these findings in relation to the human disorder geleophysic dysplasia (GD), which also arises from recessive ADAMTSL2 mutations, and recent findings in Adamtsl2-deficient mice.

Two Patients with Severe Short Stature due to a FBN1 Mutation (p.Ala1728Val) with a Mild Form of Acromicric Dysplasia

BACKGROUND

Acromicric dysplasia (AD) and geleophysic dysplasia 2 (GD2) belong to the category of acromelic dysplasia syndromes, consisting of severe short stature, short hands and feet and skin thickening. Both can result from missense mutations in the transforming growth factor beta 5 domain of the fibrillin-1 gene (FBN1).

METHODS

Two patients (P1 age 10, and P2 age 7) from unrelated families presented to their endocrinologist with severe short stature (approx. -4 SDS). They were otherwise asymptomatic and only had mild facial dysmorphisms. Extensive endocrine work-up did not reveal an underlying etiology. Exome sequencing was performed in each family.

RESULTS

Exome sequencing identified the presence of the same heterozygous missense variant c.C5183T (p.Ala1728Val) in the FBN1 gene in both P1 and P2. This variant was previously reported in a patient with GD2 and associated cardiac valvulopathy and hepatomegaly. Detailed clinical re-examination, cardiac and skeletal imaging did not reveal any abnormalities in P1 or P2 other than mild hip dysplasia.

CONCLUSION

This report broadens the phenotypic spectrum of growth disorders associated with FBN1 mutations. Identical mutations give rise to a wide phenotypic spectrum, ranging from isolated short stature to a more classic picture of GD2 with cardiac involvement, distinct facial dysmorphisms and various skeletal anomalies.

Adamtsl2 deletion results in bronchial fibrillin microfibril accumulation and bronchial epithelial dysplasia--a novel mouse model providing insights into geleophysic dysplasia

Mutations in the secreted glycoprotein ADAMTSL2 cause recessive geleophysic dysplasia (GD) in humans and Musladin–Lueke syndrome (MLS) in dogs. GD is a severe, often lethal, condition presenting with short stature, brachydactyly, stiff skin, joint contractures, tracheal-bronchial stenosis and cardiac valve anomalies, whereas MLS is non-lethal and characterized by short stature and severe skin fibrosis. Although most mutations in fibrillin-1 (FBN1) cause Marfan syndrome (MFS), a microfibril disorder leading to transforming growth factor-β (TGFβ) dysregulation, domain-specific FBN1 mutations result in dominant GD. ADAMTSL2 has been previously shown to bind FBN1 and latent TGFβ-binding protein-1 (LTBP1). Here, we investigated mice with targeted Adamtsl2 inactivation as a new model for GD (Adamtsl2^−/− mice). An intragenic lacZ reporter in these mice showed that ADAMTSL2 was produced exclusively by bronchial smooth muscle cells during embryonic lung development. Adamtsl2^−/− mice, which died at birth, had severe bronchial epithelial dysplasia with abnormal glycogen-rich inclusions in bronchial epithelium resembling the cellular anomalies described previously in GD. An increase in microfibrils in the bronchial wall was associated with increased FBN2 and microfibril-associated glycoprotein-1 (MAGP1) staining, whereas LTBP1 staining was increased in bronchial epithelium. ADAMTSL2 was shown to bind directly to FBN2 with an affinity comparable to FBN1. The observed extracellular matrix (ECM) alterations were associated with increased bronchial epithelial TGFβ signaling at 17.5 days of gestation; however, treatment with TGFβ-neutralizing antibody did not correct the epithelial dysplasia. These investigations reveal a new function of ADAMTSL2 in modulating microfibril formation, and a previously unsuspected association with FBN2. Our studies suggest that the bronchial epithelial dysplasia accompanying microfibril dysregulation in Adamtsl2^−/− mice cannot be reversed by TGFβ neutralization, and thus might be mediated by other mechanisms.

Summary: The extracellular protein ADAMTSL2 is a crucial regulator of microfibril composition in the extracellular matrix of bronchial smooth muscle cells and influences bronchial epithelial function.

Cardiac involvement in geleophysic dysplasia in three siblings of a Saudi family

Geleophysic dysplasia is an extremely rare acromelic skeletal dysplasia resembling lysosomal storage disease. It is characterised by characteristic facial phenotype, short stature, micromelia, joint contracture, and early cardiac valvular involvement. It has been described worldwide in <40 patients. Herein, we describe the cardiac features in three Saudi sisters with proved autosomal recessive geleophysic dysplasia who showed different levels of severity of their cardiac involvement.

Novel mutations in geleophysic dysplasia type 1

Geleophysic dysplasia (GD) is a rare genetic disorder characterized by acromelic dysplasia. Geleophysic dysplasia type 1 (MIM 231050) is autosomal recessive and is caused by homozygous or compound heterozygous mutation in the ADAMTSL2 (a disintegrin and metalloproteinase with thrombosponding repeats-like 2) gene. Geleophysic dysplasia type 2 (MIM 614185) is autosomal dominant and is caused by heterozygous mutation in the fibrillin 1 (FBN1) gene. Here, we present the clinical and histopathologic findings in a child with GD with newly identified ADAMTSL2 mutations. The 1st mutation was probably a pathogenic one, c.[1934G>A] p.[Arg645His], located in exon 13; the 2nd, in intron 8, was probably changing a splice site. While the light and electron microscopic findings were similar to those previously described, hydrocephalus due to aqueductal stenosis might be a new associated finding in these patients. This child with these 2 novel mutations also had an aggressive clinical course with early-onset progressive cardiac valvular disease.

Geleophysic dysplasia associated with bilateral angle closure glaucoma

In this case report, we present occurrence of bilateral angle closure glaucoma in a 9-year-old girl with geleophysic dysplasia. Bilateral YAG laser iridotomy was applied, but intraocular pressure (IOP) remained at high levels, necessitating bilateral trabeculectomy with mitomycin C. On her follow-up examinations for 3 years, IOP remained in the mid-20s with no need for further intervention or antiglaucoma medication. There are few reports describing the ocular findings of geleophysic dysplasia in literature. To our knowledge, this is the first case report describing an application of glaucoma surgery and its results at geleophysic dysplasia.

ADAMTSL2 mutations in geleophysic dysplasia demonstrate a role for ADAMTS-like proteins in TGF-beta bioavailability regulation

Geleophysic dysplasia is an autosomal recessive disorder characterized by short stature, brachydactyly, thick skin and cardiac valvular anomalies often responsible for an early death. Studying six geleophysic dysplasia families, we first mapped the underlying gene to chromosome 9q34.2 and identified five distinct nonsense and missense mutations in ADAMTSL2 (a disintegrin and metalloproteinase with thrombospondin repeats-like 2), which encodes a secreted glycoprotein of unknown function. Functional studies in HEK293 cells showed that ADAMTSL2 mutations lead to reduced secretion of the mutated proteins, possibly owing to the misfolding of ADAMTSL2. A yeast two-hybrid screen showed that ADAMTSL2 interacts with latent TGF-beta-binding protein 1. In addition, we observed a significant increase in total and active TGF-beta in the culture medium as well as nuclear localization of phosphorylated SMAD2 in fibroblasts from individuals with geleophysic dysplasia. These data suggest that ADAMTSL2 mutations may lead to a dysregulation of TGF-beta signaling and may be the underlying mechanism of geleophysic dysplasia.

Natural history of cardiac involvement in geleophysic dysplasia

Geleophysic dysplasia is an autosomal recessive short-limbed, dysmorphic syndrome. The condition is frequently associated with cardiac valvular disease, which may result in secondary hypertrophy and cardiac failure. We describe two distantly related Pakistani children with classical features of geleophysic dysplasia. Pulmonary stenosis was recognized in both within a few months of birth. The younger child shows no signs of cardiac decompensation at the age of 7 years whilst her older cousin has developed a significant pulmonary gradient requiring surgical intervention in the second decade of life. The natural history of his disorder highlights that the cardiac involvement seen in apparently stable forms of geleophysic dysplasia is frequently progressive.

Post-natal short stature, short limbs, brachydactyly, facial abnormalities, and delayed bone age: a new syndrome?

A boy is described with clinical features including post-natal short stature, short limbs, speech delay, relatively large skull, prominent metopic ridge, wide palpebral fissures, proptosis, epicanthic folds, capillary hemangioma between the eyes and nose, flat nasal bridge, everted and small nares, small ears with a narrow external auditory canal and thick lobes, short neck, brachydactyly, bilateral Simian creases, a single flexion crease of the first and fifth fingers, protruding abdomen, and bilateral cryptorchidism. Radiographs did not show any features of bone dysplasia. However, a delayed bone age was noted. The boy's parents are first cousins. To the best of our knowledge, this constellation of anomalies has not been reported before, and may be considered a new syndrome.

Acromicric dysplasia: long term outcome and evidence of autosomal dominant inheritance

Acromicric dysplasia is a rare bone dysplasia characterised by short stature, short hands and feet, normal intelligence, mild facial dysmorphism, and characteristic x ray abnormalities of the hands. Only a very small number of children with this condition have been reported so far. Here we report on a series of 22 patients including 10 boys and 12 girls with acromicric dysplasia. Length was normal at birth and height fell progressively off the centiles postnatally. The mean adult height was 130 cm (133 cm in males, 129 cm in females). The hands, feet, and limbs were short and OFC was normal. Intelligence was normal and mild dysmorphic features were noted. Other occasional features included well developed muscles, a hoarse voice, generalised joint limitation in some patients, frequent ear, tracheal, and respiratory complication, and spine abnormalities. Long term follow up showed that facial dysmorphism was less obvious in adults and that carpal tunnel syndrome was frequent in older patients. Apart from short metacarpals and phalanges, internal notch of the second metacarpal, external notch of the fifth metacarpal, and internal notch of the femoral heads, there were no major x ray abnormalities. No major complications, such as cardiac disease or major orthopaedic problems, occurred in the course of the disease. The condition appeared to be sporadic in 16 cases but the observation of vertical transmission in three families was consistent with an autosomal dominant mode of inheritance.

Geleophysic dysplasia: Report on two sibs

The authors describe two additional cases of Geleophysic dysplasia in siblings, which is a rare autosomal recessive disorder of glycoprotein metabolism whose basic defects remain to be determined.