Molecular nosology of heritable disorders of connective tissue

The Musculoskeletal Manifestations of Marfan Syndrome: Diagnosis, Impact, and Management

Purpose of Review

Marfan syndrome (MFS) is an autosomal dominant heritable disorder of fibrillin-1 (FBN1) with predominantly ocular, cardiovascular, and musculoskeletal manifestations that has a population prevalence of approximately 1 in 5–10,000 (Chiu et al. Mayo Clin Proc. 89(1):34–42, 146, Dietz 3, Loeys et al. J Med Genet. 47(7):476–85, 4).

Recent Findings

The vascular complications of MFS still pose the greatest threat, but effective management options, such as regular cardiac monitoring and elective surgical intervention, have reduced the risk of life-threatening cardiovascular events, such as aortic dissection. Although cardiovascular morbidity and mortality remains high, these improvements in cardiovascular management have extended the life expectancy of those with MFS by perhaps 30–50 years from an estimated mean of 32 years in 1972 (Dietz 3, Gott et al. Eur J Cardio-thoracic Surg. 10(3):149–58, 147, Murdoch et al. N Engl J Med. 286(15):804–8, 148). The musculoskeletal manifestations of MFS, which to date have received less attention, can also have a significant impact on the quality of life and are likely to become more important as the age of the Marfan syndrome population increases (Hasan et al. Int J Clin Pract. 61(8):1308–1320, 127). In addition, musculoskeletal manifestations are often critically important in the diagnosis of MFS.

Summary

Here, we review the main clinically relevant and diagnostically useful musculoskeletal features of MFS, which together contribute to the “systemic features score” (referred to hereafter as systemic score), part of the revised Ghent nosology for MFS. We discuss current treatment strategies and highlight the need for a multidisciplinary approach to diagnosis and management. Finally, we review new pharmacological approaches that may be disease modifying and could help to improve the outcome for individuals with this syndrome.

Benefits of ketogenic diet in a pediatric patient with Ehlers-Danlos syndrome and STXBP1-related epileptic encephalopathy

PURPOSE/AIM

Ehlers-Danlos syndrome (EDS) is a hereditary connective tissue disease. Epilepsy is not a common neurological finding in EDS. Here we report a pediatric patient with EDS comorbid with STXBP1 related epileptic encephalopathy as 'electrical status epilepticus during slow-wave sleep (ESES)' and whose refractory epileptic seizures were controlled with ketogenic diet.

CASE REPORT

A 6-year-old girl who had EDS presented with refractory seizures and worsening cognitive functions. Her sleep electroencephalography (EEG) revealed electrical status epilepticus during slow-wave sleep (ESES). The epileptic encephalopathy panel revealed a de novo c.560C > T (p.pro187Leu) heterozygous mutation in the STXPB1 gene. Ketogenic diet treatment was started for her refractory seizures and seizures stopped in the third month of the 3:1 classical ketogenic diet.

CONCLUSION

Our case is remarkable due to the coexistence of EDS and epileptic encephalopathy as well as ESES findings in STXBP1-associated epileptic encephalopathy and is therefore presented. Ketogenic diet would be beneficial on the management of refractory seizures in STXBP1-related epileptic encephalopathy and ESES.

The Clinic Is My Laboratory: Life as a Clinical Geneticist

Clinical genetics is the application of advances in genetics and medicine to real human families. It involves diagnosis, care, and counseling concerning options available to affected individuals and their family members. Advances in medicine and genetics have led to dramatic changes in the scope and responsibilities of clinical genetics. This reflection on the last 50+ years of clinical genetics comes from personal experience, with an emphasis on the important contributions that clinical geneticists have made to the understanding of disease/disorder processes and mechanisms. The genetics clinic is a research laboratory where major advances in knowledge can and have been made.

A group of patients with Marfan's syndrome, who have finger and toe contractures, displays tendons' alterations upon an ultrasound examination: are these features common among classical Marfan patients?

The involvement of the musculoskeletal system with other mild pleiotropic manifestations represents a clinical criterion, called "systemic features," to d iagnose Marfan's syndrome. We aimed to investigate the features of the hands and feet redressable contractures present in a group of Marfan patients. In 13 patients with previously diagnosed Marfan's syndrome, an accurate clinical examination was performed. In particular the characterization of the musculoskeletal system by visual analogic scale to measure muscle pain (VAS) and muscle strength (MRC system) was carried out; the Beighton scale score was used to evaluate the articular hypermobility. Ultrasound examination (US) was performed to detect deep-superficial flexor tendons and extensor tendons of both hands, and the short and long flexor and extensor tendons of the fingers and toes in static and dynamic positions. The ImageJ program was adopted to measure a profile of tendon echo-intensity. A reduction of the thickness of all tendons was detected by US in our patients; the VAS and Beighton scale scores were in normal ranges. The profile of tendon echo-intensity showed different textural details in all Marfan patients. This study provides evidence for other contractures' localization, and for altered findings of the tendons in patients with Marfan syndrome and finger/toe contractures. These changes may be associated with structural modifications in connective tissue.

Ehlers-Danlos syndrome and neurological features: a review

Ehlers-Danlos Syndrome is a term that comprises a variety of inherited connective tissue disorders characterized primarily by skin hyperextensibility, joints hypermobility and excessive dislocations, easy bruisability, generalized fragility. If much is known about orthopedic or physiatric features of this syndrome, poor is known about the neurological ones. Thus neurological assessment is very important due to the possible various clinical manifestations in this syndrome.

Hereditary connective tissue diseases in young adult stroke: a comprehensive synthesis

Though the genetic background of ischaemic and haemorrhagic stroke is often polygenetic or multifactorial, it can in some cases result from a monogenic disease, particularly in young adults. Besides arteriopathies and metabolic disorders, several connective tissue diseases can present with stroke. While some of these diseases have been recognized for decades as causes of stroke, such as the vascular Ehlers-Danlos syndrome, others only recently came to attention as being involved in stroke pathogenesis, such as those related to Type IV collagen. This paper discusses each of these connective tissue disorders and their relation with stroke briefly, emphasizing the main clinical features which can lead to their diagnosis.

Multiple spontaneous coronary artery ruptures and cardiac tamponade in vascular Ehlers-Danlos syndrome

We report a case of a 45-year-old woman with Ehlers-Danlos syndrome (EDS) type IV, the vascular type, who presented with multiple coronary artery ruptures causing cardiac tamponade. She had sudden onset of chest pain soon after transarterial embolization for right carotid-cavernous fistula. Transthoracic echocardiography confirmed cardiac tamponade and hypokinetic inferolateral wall. Enhanced CT and transesophageal echocardiography ruled out aortic dissection. Coronary angiography showed contrast extravasation from multiple sites of the right coronary artery and left circumflex coronary artery. We suspected EDS type IV, and a skin biopsy for DNA and RNA analysis was done after taking written informed consent. Polymerase chain reaction (PCR) and sequencing of the PCR product showed a heterozygous missense mutation of codon 85 in the COL3A1 gene, which converted glycine to aspartic acid, and thus a diagnosis of EDS type IV was established. To our best knowledge, this is the first case of EDS type IV causing multiple coronary artery ruptures.

Musculoskeletal complaints, physical activity and health-related quality of life among patients with the Ehlers-Danlos syndrome hypermobility type

PURPOSE

To investigate the musculoskeletal complaints, physical activity (PA) and health-related quality of life (HRQoL) in patients with the Ehlers-Danlos syndrome hypermobility type (EDS-HT).

METHODS

Thirty-two female EDS-HT patients as defined by the Villefranche criteria and 32 gender- and age-matched healthy control subjects participated in the study. Data about musculoskeletal complaints were collected from a specific form developed for the study. Daily PA and HRQoL were evaluated by the Baecke questionnaire and the RAND 36-Item Health Survey (distributed by RAND), respectively.

RESULTS

A significant presence of joint pain, joint dislocations, muscle cramps, tendinitis, fatigue and headache were revealed in the EDS-HT patient group. Joint pain was reported as the most frequent and most severe symptom. The habitual PA level was diminished in the patient group. Specifically, EDS-HT subjects had significantly lower sport participation, but a comparable leisure time excluding sports compared to the healthy control subjects. All eight HRQoL dimensions of the RAND-36 and both physical and emotional summary scores were significantly impaired in EDS-HT.

CONCLUSIONS

EDS-HT is characterised by various severe musculoskeletal complaints and has a detrimental effect on the habitual level of PA and HRQoL, in both physical and psychosocial dimension. An appropriate treatment and management in healthcare is needed.

Three-dimensional analysis of the vertebral rotation associated with the lateral deviation in Marfan syndrome spinal deformity

Marfan syndrome (MFS) is a genetic disease often marked with the presence of scoliosis, which is poorly described in the literature. No three-dimensional analysis of the deformity in the literature is observed. Thirty patients diagnosed with MFS were prospectively included in our series. Each patient was proposed to undergo a stereoradiographic examination of the spine. Personalized three-dimensional reconstruction from T1 to L5 of the spine were made. The Cobb angle of each curve and the axial rotation of each vertebra were assessed. Our aim was to assess whether there is a correlation between the Cobb angle and the axial vertebral rotation at the apex of the curves associated with MFS. Fourteen females and 16 males were included. The mean age was 25.9 years, ranging from 4 to 65 years. Eleven patients were under 16 years. Nineteen patients were defined as scoliotic (Cobb angle over 10 degrees ), and 11 were defined as nonscoliotic (Cobb angle under 10 degrees ). A strong correlation (Pearson) between the Cobb angle and the axial vertebral rotation at the apex of the curves associated with MFS was observed. This is the first step of a three-dimensional analysis of the scoliosis associated with MFS. This study pointed out that the vertebral axial rotation in scoliosis associated with MFS compared with that observed in adolescent idiopathic scoliosis and in scoliosis associated with cerebral palsy patients.

LEVEL OF EVIDENCE

II (Diagnostic Study).

Scoliotic curve patterns in patients with Marfan syndrome

PURPOSE

Cases of "non-idiopathic" scoliosis are deemed atypical. These require a comprehensive work-up in order to choose the best treatment (and to determine an extent of fusion if needed). Marfan syndrome (MFS) is a genetic disease often marked with the presence of scoliosis, which is poorly described in the literature. Knowing that the clinical diagnosis of MFS is not always obvious, we investigated how atypical the scoliosis associated with MFS was when compared with that of adolescent idiopathic scoliosis (AIS).

METHODS

In our series, we included 30 patients diagnosed with MFS. Each patient was proposed to undergo a plain radiographic examination of the spine. Scoliotic patients were classified according to the Scoliosis Research Society (SRS) curve pattern classification. Curve patterns with a very low rate of occurrence in historic control were defined as "atypical".

RESULTS

A total of 19 patients were defined as scoliotic. In 9 cases, the curve pattern was atypical. In the other 10, the curve pattern was typical, but a fine analysis revealed some atypical features in the position of the apex and end vertebrae.

CONCLUSIONS

Scoliosis associated with MFS was found to be atypical in all cases. This supports the idea that an atypical curve pattern should be considered as an argument in favour of a non-idiopathic aetiology and, therefore, an appropriate work-up should be performed before deciding treatment.

Sagittal balance in scoliosis associated with Marfan syndrome: a stereoradiographic three-dimensional analysis

PURPOSE

Marfan syndrome (MFS) is a genetic disease often marked by the presence of scoliosis. There is no three-dimensional analysis of the deformity in the literature. Our aim was to determine what kind of sagittal balance defines scoliosis associated with MFS, namely a flexion deformity, as it is in scoliosis associated with Chiari I or an extension deformity, as in adolescent idiopathic scoliosis (AIS). To address this issue, we compared the presence or absence of a thoracic scoliosis with the presence or absence of a segment in extension in the thoracic spine.

METHODS

In our series, 30 patients diagnosed with Marfan syndrome were prospectively included. In each patient, personalized three-dimensional reconstruction from T1 to L5 of the spine was made using stereoradiography. The patients were first separated based on the presence or absence of thoracic scoliosis, in order to compare this with the presence or absence of a segment in extension in the thoracic spine. They were then classified into two groups based on the presence or absence of the segment in extension (meaning containing negative values of inter-vertebral sagittal rotation) in the thoracic spine.

RESULTS

Among scoliotic patients with a thoracic scoliosis (17 cases), there were 13 (76.5% cases) with a segment in extension in the thoracic spine and 4 with no segment in extension.

CONCLUSIONS

Our results showed that scoliosis associated with MFS is somehow original, demonstrating a sagittal balance in extension (as AIS) in about 80% of thoracic curves, but without this characteristic feature in about 20%.

Subependymal periventricular heterotopias in a patient with ehlers-danlos syndrome: a new case

Ehlers-Danlos syndrome is a complex hereditary connective tissue disorder that is characterized by abnormalities of the skin and joints and visceral and neurological manifestations. At present, at least 11 forms are recognized on the basis of their clinical characteristics, methods of transmission, and biochemical defect. The neurologic manifestations include cerebrovascular disease, peripheral neuropathy, plexopathy, periventricular subependymal heterotopias, and epilepsy. Previously, 2 females were reported to be affected with subependimal periventricular heterotopias and Ehlers-Danlos syndrome type 1. The authors report a new case of a 12-year-old girl with similar clinical and neuroradiological features.

Clinical Features of Ehlers-Danlos Syndrome

BACKGROUND/PURPOSE

Ehlers-Danlos syndrome (EDS) is a clinically and genetically heterogeneous connective tissue disorder characterized by hyperextensibility of the skin, hypermobility of joints, and tissue fragility. This retrospective study analyzed the characteristics of patients with EDS.

METHODS

Review of medical records identified 16 cases of EDS during the study period from November 1997 to October 2002. Data on these patients, including clinical presentation, physical examinations, Beighton score, echocardiogram, bone mineral density findings and clinical classification, were analyzed.

RESULTS

The age of the patients ranged from 13 months to 36 years. All patients had skin hyperextensibility, joint hypermobility (Beighton score > 5 points), and tissue fragility. Complete bone mineral density study was performed in 11 patients and revealed that all had osteoporosis. Echocardiographic study was performed in 14 patients and showed aortic root dilatation/valve prolapse in 6/14 (43%). Other common features of EDS had the following prevalence: premature rupture of membranes in 3/16 (19%); prematurity in 3/16 (19%); neonatal hypotonia in 5/16 (31%); congenital hip dislocation in 3/16 (19%); unstable gait in 7/16 (44%); bone fracture(s) in 3/16 (19%); motor delay in 3/16 (19%); scoliosis in 3/16 (19%); short stature in 7/16 (44%); and positive family history in 8/16 (50%). All patients had a Beighton score of more than 5 points.

CONCLUSION

The results of this study emphasize the importance of echocardiographic monitoring of aortic size and valvular condition, and assessment of bone mineral density in patients with EDS. Clinical evaluation and counseling should be undertaken prior to pregnancy in patients with EDS because of the risk from labor and vaginal delivery in patients with type IV and the inability to distinguish EDS subtypes in Taiwan due to the unavailability of biochemical assay or molecular mutation analysis as part of standard care.

Polymorphism in signal transduction is a major route through which osteoarthritis susceptibility is acting

PURPOSE OF REVIEW

In the last year there has been considerable success in the identification of genes harbouring susceptibility for primary osteoarthritis. This report brings the reader up-to-date by focusing on three of the more compelling finds.

RECENT FINDINGS

A UK group reported an association of the FRZB gene with hip osteoarthritis in females. FRZB codes for secreted frizzled-related protein 3, an antagonist of Wnt signalling. The Wnt signal transduction pathway is critical for normal development and is also active in adult tissues. Secreted frizzled-related protein 3 helps to maintain articular cartilage and the associated alleles at FRZB reduce the activity of this important protein. A Japanese group has reported an association of the asporin gene ASPN with knee and hip osteoarthritis and an association of the calmodulin 1 gene CALM1 with hip osteoarthritis. Asporin is a cartilage extracellular protein that regulates the activity of transforming growth factor-beta. Calmodulin is an intracellular protein that interacts with a number of proteins involved in signal transduction. The associated alleles at ASPN and CALM1 reduce the ability of chondrocytes to express the genes encoding aggrecan and type II collagen. Since these are essential structural components of articular cartilage, the ASPN and CALM1 associations are predicted to adversely affect the maintenance of cartilage.

SUMMARY

The FRZB, ASPN and CALM1 results are compelling and highlight that polymorphism in signal transduction pathways is a major component of osteoarthritis susceptibility. This is an exciting observation since signal transduction pathways are malleable and therefore potentially amenable to intervention and modification.

Ehlers-Danlos syndrome and periventricular nodular heterotopia in a Spanish family with a single FLNA mutation

BACKGROUND

The Ehlers-Danlos syndrome (EDS) comprises a group of hereditary connective tissue disorders. Periventricular nodular heterotopia (PNH) is a human neuronal migration disorder characterised by seizures and conglomerates of neural cells around the lateral ventricles of the brain, caused by FLNA mutations. FLNA encodes filamin A, an actin binding protein involved in cytoskeletal organisation. The amino-terminal actin binding domain (ABD) of filamins contains two tandem calponin homology domains, CHD1 and CHD2.

OBJECTIVE

To report clinical and genetic analyses in a Spanish family affected by a connective tissue disorder suggestive of EDS type III and PNH.

METHODS

A clinical and molecular study was undertaken in the three affected women. Clinical histories, physical and neurological examinations, brain magnetic resonance imaging studies, and skin biopsies were done. Genetic analysis of the FLNA gene was undertaken by direct sequencing and restriction fragment length polymorphism analysis.

RESULTS

Mutation analysis of the FLNA gene resulted in the identification of a novel mutation in exon 3 (c.383C-->T) segregating with the combination of both syndromes. This mutation results in a substitution of an alanine residue (A128V) in CHD1.

CONCLUSIONS

The findings suggest that the Ala128Val mutation causes the dual EDS-PNH phenotype. This association constitutes a new variant within the EDS spectrum. This is the first description of a familial EDS-PNH association with a mutation in FLNA.

Ehlers-Danlos syndrome type IV with a unique point mutation in COL3A1 and familial phenotype of myocardial infarction without organic coronary stenosis

We report on a 43-year-old male patient with Ehlers-Danlos syndrome (EDS) type IV with acute myocardial infarction (MI) without organic coronary stenosis. The disease was complicated with pneumothorax, subcutaneous and mediastinal emphysema, and splenic artery rupture. Three of the patient's family members suffered sudden cardiac death or MI. A diagnosis of EDS type IV was confirmed by decreased production of type III collagen by 86%. Mutation analysis revealed a point mutation in the COL3A1 gene that substituted glycine for aspartate at amino acid position 877. This mutation had not been reported as pathogenic for EDS type IV. These findings suggest close linkage between the mutation and the phenotype with familial MI.

Recurrent ventral herniation in Ehlers-Danlos syndrome

Ehlers-Danlos syndrome is an inherited collagen disorder characterized by skin hyperextensibility, joint laxity, and tissue friability. In this study, it was hypothesized that Ehlers-Danlos syndrome is frequently undiagnosed in patients who present for repair of ventral abdominal wall hernias. A retrospective chart review was conducted, and patients who had presented for elective repair of recurrent abdominal wall herniation were identified. In all patients, one or more prior attempts at repair with either mesh or autologous tissues had failed. Patients in whom abdominal wall components were lost secondary to extirpation or trauma, patients who had required acute closure, and patients with less than 2 months of follow-up were excluded. Twenty patients met these criteria. Twenty cases of recurrent ventral hernia repairs were reviewed, with special attention to identification of the preoperative diagnosis of Ehlers-Danlos syndrome. Patients ranged in age from 29 to 75 years, with a mean age of 54 years. Five patients were male (25 percent), and 15 were female (75 percent). The majority (95 percent) were Caucasian. The most common initial procedures were gynecologic in origin (35 percent). A precise closure technique that minimizes recurrence after ventral hernia repairs was used. With use of this technique, there was only one recurrence over a follow-up period that ranged from 2 to 60 months (mean follow-up duration, 25.7 months). Two patients with Ehlers-Danlos syndrome were identified, and their cases are presented in this article. The "components separation" technique with primary component approximation and mesh overlay was used for defect closure in the two cases presented. The identification of these two patients suggests the possibility of underdiagnosis of Ehlers-Danlos syndrome among patients who undergo repeated ventral hernia repair and who have had previous adverse postoperative outcomes. There are no previous reports in the literature that address recurrent ventral abdominal herniation in patients with Ehlers-Danlos syndrome.

Dispersal of radioisotope labelled solution following deep dermal injection in Ehlers-Danlos syndrome

Ehlers-Danlos syndrome (EDS) is the commonest inherited disorder of connective tissue, affecting around 10 000 patients in the UK. Patients with EDS have reported that local anaesthetic is often ineffective. Patients with less severe skin laxity often have the most problems. We have postulated that this resistance to local anaesthetics is not due to the lax connective tissues as is often assumed. This study used radioactively labelled solution ((99m)Tc-pertechnetate) administered as a deep dermal injection in the forearm. The rate of dispersal of isotope was measured over 60 min and found to be identical between six patients with EDS and three controls. The effects of local anaesthetics are complex and depend on the individual chemical properties of the agent and a number of tissue factors. This study would suggest that the lack of effectiveness of local anaesthetic solutions is not due to rapid dispersal of solution. It is unlikely therefore that its lack of effect can be compensated for by simply increasing the amount used. The diagnosis of EDS should be considered in any patient who complains unexpectedly of pain during their procedure, particularly when the surgeon knows that an adequate volume of local anaesthetic has been used.

Peripheral resistance vessel dysfunction in Marfan syndrome

BACKGROUND

Patients with Marfan syndrome show a hereditary abnormality of elastin metabolism that may cause aortic enlargement and dissection. We have hypothesized that abnormal elastin may alter peripheral vascular structure and function.

METHODS

Forearm blood flow (FBF) (in milliliters per minute per 100 mL) response to the endothelium-dependent dilator acetylcholine (0.75 to 4.5 microg/min per 100 mL), the endothelium-independent dilator sodium nitroprusside (0.05 to 0.3 microg/min per 100 mL), and structure-related maximum dilator response (10-minute occlusion-induced reactive hyperemia) were measured by plethysmograph in 10 patients with Marfan syndrome (mean age 44 years) and 10 healthy age- and sex-matched controls. Patients with the complications of hypercholesterolemia, diabetes mellitus, or heart failure were excluded from the study.

RESULTS

Basal FBF (mean +/- SE) did not differ between the 2 groups (2.7 +/- 0.3 vs 2.3 +/- 0.4). Maximum FBF response to acetylcholine in patients with Marfan syndrome was significantly lower than that of healthy controls (8.5 +/- 2.1 vs 15.4 +/- 1.7 mL/min per 100 mL; P <.05). Reactive hyperemia was also lower in patients with Marfan syndrome (at peak 23.0 +/- 2.5 vs 29.5 +/- 2.3 mL/min per 100 mL; P <.05), but sodium nitroprusside-induced FBF changes did not differ between the 2 groups (10.3 +/- 1.1 vs 10.2 +/- 1.5 mL/min per 100 mL; P = not significant).

CONCLUSION

These observations suggest that endothelium-dependent dilation and maximum dilator reserve capacity are both abnormal in peripheral resistance vessels of patients with Marfan syndrome. These peripheral vasomotion abnormalities may have a detrimental impact on the cardiovascular system in this disorder.

Dexamethasone-induced healing of chronic leg ulcers in a patient with defective organization of the extracellular matrix of fibronectin

Previous investigations have shown that skin fibroblasts derived from patients affected by Ehlers-Danlos syndrome (EDS) lack an organized extracellular matrix (ECM) of fibronectin (FN). As retarded wound healing is a sign of EDS, we hypothesized that a young healthy man suffering from chronic recalcitrant leg ulcers might be affected by a defect of FN-ECM organization similar to that observed in EDS. Immunofluorescence of cultured skin fibroblasts obtained from skin biopsies from the patient and a control demonstrated that the patient's fibroblasts lacked FN-ECM organization, in contrast with those of the control; this was restored by 10-7 mol/L dexamethasone (DEX) in vitro. DEX treatment of the patient was associated with healing of his leg ulcers. In conclusion, DEX may be effective in reversing impaired wound healing associated with a lack of FN-ECM organization

Ehlers-Danlos syndrome has varied molecular mechanisms

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An exon skipping mutation of a type V collagen gene (COL5A1) in Ehlers-Danlos syndrome

The Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders characterised by skin hyperextensibility, joint hypermobility, easy bruising, and cutaneous fragility. Nine discrete clinical subtypes have been classified. We have investigated the molecular defect in a patient with clinical features of Ehlers-Danlos syndromes types I/II and VII. Electron microscopy of skin tissue indicated abnormal collagen fibrillogenesis with longitudinal sections showing a marked disruption of fibril packing giving very irregular outlines to transverse sections. Analysis of the collagens produced by cultured fibroblasts showed that the type V collagen had a population of alpha 1 (V) chains shorter than normal. Peptide mapping suggested a deletion within the triple helical domain. RTPCR amplification of mRNA covering the whole of this domain of COL5A1 showed a deletion of 54 bp. Although six Gly-X-Y triplets were lost, the essential triplet amino acid sequence and C-propeptide structure were maintained allowing mutant protein chains to be incorporated into triple helices. Genomic DNA analysis identified a de novo G+3-->T transversion in a 5' splice site of one COL5A1 allele. This mutation is analogous to mutations causing exon skipping in the major collagen genes, COL1A1, COL1A2, and COL3A1, identified in several cases of osteogenesis imperfecta and EDS type IV. These observations support the hypothesis that type V, although quantitatively a minor collagen, has a critical role in the formation of the fibrillar collagen matrix.

Hypercalciuria in osteogenesis imperfecta: a follow-up study to assess renal effects

In 1991, we reported that hypercalciuria is a common finding in our pediatric patient population with osteogenesis imperfecta (OI) (17 of 47 = 36%). Here, we prospectively screened 12 of these hypercalciuric children, on average 4 years subsequent to the discovery of elevated urine calcium levels, for adverse effects on renal function. Despite an ad libitum decrease since initial investigation of about 30% in their previously normal dietary calcium intake (adjusted for body weight), 8 of the 12 patients remained hypercalciuric (urine calcium/creatinine > 0.62 mmol/mmol). We found, once again, that urinary calcium levels significantly correlated with the severity of the skeletal disease as assessed by z-score for height (r = -0.75, p = 0.005). Evaluation of kidney function, however, revealed: (i) normal routine urinalysis in all but 1 subject who had transient microscopic hematuria; (ii) unremarkable concentrating ability determined by fasting urine osmolality; (iii) normal creatinine clearance, and (iv) unremarkable ultrasonography to measure renal size and to screen for nephrocalcinosis or nephrolithiasis. Although no significant renal compromise was detected with these studies in our hypercalciuric pediatric OI patients, investigation of affected adults, especially those severely affected, will be important to assess whether this is a long-term problem and if adverse effects on the kidneys do develop.

Caenorhabditis elegans sqt-3 mutants have mutations in the col-1 collagen gene

sqt-3 mutants of Caenorhabditis elegans form dumpy larvae and adults and display allele-specific defects in locomotion, fertility, and viability. We have determined that the sqt-3 locus encodes COL-1 collagen. We physically mapped the col-1 gene to a cosmid on chromosome V whose position is consistent with the location of the sqt-3 gene. We also observed morphological defects in sqt-3 mutants at stages that correlate with the mRNA expression patterns of col-1. Sequence analysis of the col-1 gene in the three temperature-sensitive mutants revealed that each allele of sqt-3 has a unique missense mutation causing arginine or glutamic acid to replace glycine in a Gly-X-Y triple helical domain. These glycine substitutions may result in longer non-collagenous domains, which may decrease the thermal stability or impart additional flexibility to mutant trimers. In addition, we describe four corrections to the published sequence of col-1, including one fifteen nucleotide addition that completes a conserved domain in the amino terminal coding region.

Autosomal dominant spondylarthropathy due to a type II procollagen gene (COL2A1) point mutation

Osteoarthrosis represents a very common disease with heterogeneous etiology. In some pedigrees linkage of the condition with the type II collagen gene (COL2A1) has been established, but information on the underlying gene defect is still incomplete as only one mutation causing this phenotype has been identified. We analyzed the COL2A1 gene in a 27-year-old woman and her 47-year-old mother presenting with severe premature osteoarthrosis and X-ray signs compatible with mild spondyloepiphyseal dysplasia. Examination of the complete gene in both patients was done by amplification of all 54 exons, screening of the PCR products by SSCP-analysis, and subsequent sequencing. In mother and daughter a G to A transition at the 5'-end of exon 21 was detected, leading to a substitution of serine for glycine at position 274 of the triple helical domain. The mutation was not present in unaffected family members or in healthy control individuals. The autosomal dominant spondylarthropathies may represent the less severe entities of the clinical spectrum of type II collagenopathies.

Mutations in von Recklinghausen neurofibromatosis: an hypothesis

Von Recklinghausen neurofibromatosis or neurofibromatosis type I (NF1) is a relatively frequent (1/3,000 livebirths) autosomal dominant condition. Some unusual aspects are noted in this disorder: new mutations are frequent and almost all are of paternal origin without parental age effect. The recurrence of NF1 among children of healthy parents is rare as opposed to other dominant disorders. I propose that in NF1 (1) new mutations occur often in somatic cells or in late germinal cells, however, they occur very rarely in early germinal cells leading to germinal mosaicism and (2) the individual with somatic mosaicism presents symptoms of the disease. Therefore, an NF1 patient with an apparent new mutation is often a somatic mosaic for the mutation and if the mosaic is also present in germinal cells some of his children will be affected. This hypothesis may explain the unusual aspects of mutation in NF1.