Achondrogenesis

In this issue of Pediatric and Developmental Pathology, Aigner and colleagues report a detailed investigation of cartilage matrix changes in a 14-week fetus with achondrogenesis type IA. The changes reported differ from matrix alterations observed in achondrogenesis types IB or II and provide insight into the phenotypic and genotypic differences within this group of skeletal dysplasias.

Osteogenesis imperfecta

Osteogenesis imperfecta is a relatively common hereditary connective tissue disorder characterized by bone fragility and fractures. Other frequently affected tissues include tendons, ligaments, skin, sclera, teeth, and middle and inner ear. Molecular studies have demonstrated that most cases result from mutations affecting the genes responsible for the formation of type 1 collagen. The phenotypic presentation varies from mild to lethal. Commonly observed dental abnormalities include dentinogenesis imperfecta and malocclusion. Medical therapies using bisphosphonates have resulted in reduced fracture risk and decreased bone pain. To date, no cases of bisphosphonate-associated osteonecrosis have been reported. With appropriate precautions, the patient with osteogenesis imperfecta can tolerate and benefit from the delivery of necessary dental care to control oral disease, improve function, and improve esthetics.

[Genetic collagen disorders and the impact on craniofacial development]

Extracellular matrix molecules provide to tissues their mechanical properties and constitute a reservoir of local or regional signals that regulate cellular function. Collagens, the major components of osseous and collagenous matrices, have structural similarities, but are encoded by different genes. We describe here osteogenesis imperfecta, a collagen I, the principal constituent of bone, genetic disease, and its craniofacial implications. By comparing it with genetic disorders of cartilage collagen (Kniest and Stickler syndromes) we try to clarify the respective influences of these matrix molecules upon craniofacial development.

The effect of cyclical intravenous pamidronate in children and adolescents with osteogenesis imperfecta type V

Intravenous treatment with pamidronate is beneficial in children and adolescents with moderate to severe forms of osteogenesis imperfecta (OI) types I, III and IV, but there is little information on the effects of this treatment on the newly described OI type V. Here, we describe the results of 2 years of pamidronate treatment in 11 children and adolescents with OI type V (age at start of therapy 1.8 to 15.0 years; 6 girls). Pamidronate was given in intravenous cycles at a cumulative yearly dose of 9 mg/kg. The first infusion cycle was associated with fever and mild hypocalcemia in most patients, but no other short-term side effects were noted. Two years of pamidronate treatment led to a decrease in the urinary excretion of N-terminal telopeptide of type I collagen to 50% of baseline levels. Both the size and volumetric bone mineral density of lumbar vertebrae increased compared to age- and sex-matched reference data (P < 0.05 in both cases). Histomorphometry of transiliac bone samples showed an average increase of 86% in cortical thickness (N = 7; P = 0.005). No significant changes with treatment were observed in the age-related z scores of isometric maximal grip force and height. Fracture incidence decreased from 1.5 fractures per year before treatment to 0.5 fractures per year during the fist 2 years of treatment. Ambulation status improved in four patients and remained unchanged in the others. In conclusion, the intravenous pamidronate therapy has a similar effect in OI type V as it has in the other OI types.

[Idiopathic and secondary osteoporosis in childhood]

Osteoporosis is a common disease characterized by reduced bone mass, with a consequent increase in bone fragility and susceptibility to fracture risk. Bone mineral density (BMD) measurement is used to make the diagnosis of osteoporosis prior to incident fracture, and to predict fracture risk. BMD is determined by the peak bone mass achieved, and the rate and timing of subsequent bone loss. Dual-energy X-ray absorptiometry (DEXA) is the most popular and effective method utilized for osteoporosis screening. Bone disease is a side effect of concern regarding chronic glucocorticoid (GC) administration. Most GC-treated patients exhibit a process of bone loss, frequently leading to osteoporosis, with increased fracture risk, especially in spinal vertebrae. Osteogenesis imperfecta is an inherited and generalized connective tissue disorder characterized mainly by bone fragility. Idiopathic osteoporosis of childhood or adolescence without blue sclerae and other stigmata of osteogenesis imperfecta is occasionally observed and sometimes more than one sib is affected. Beta-thalassemia major is associated with significant bone disease. The etiology of the bone disease is still debatable, many factors can adversely affect bone accretion in thalassemic patients. These include delayed puberty, bone marrow expansion, the deleterious effects of desferrioxamine, iron overload and genetic factors. Current treatment alternatives of osteoporosis include bisphosphonates, calcitonin, and selective estrogen receptor modulators.

Avaliação clínica, radiográfica e laboratorial de pacientes com osteogênese imperfeita

BACKGROUND

Osteogenesis imperfecta is a genetic disorder characterized by defects in type I collagen. The main symptom is bone fragility and susceptibility to fractures. Other clinical findings are dentinogenesis imperfecta, blue sclera, early deafness and joint laxity. The purpose of this paper is to establish a practical relationship of the clinical differences between the Sillence's groups.

METHODS

22 patients were classified according to Sillence et al criteria and submitted to laboratory tests including blood calcium level and bone densitometry.

RESULTS

All clinical and laboratory differences were discussed in the text.

CONCLUSIONS

Differences such as results that were found in walking ability, height and bone densitometry were significant and may help to classify patients and to establish prognosis.

Cyclic bisphosphonate therapy in osteogenesis imperfecta type V

The clinical and radiographic features and management of a young person with recently delineated Osteogenesis Imperfecta Type V is described. A female aged 9 years presented with a history of multiple fractures since 3 years of age and bilateral dislocation of the elbows from infancy. She was commenced on a low dose frequent regimen of cyclic intravenous pamidronate, which resulted in progressive improvement in bone density, reduced fracture frequency and remission of symptoms of osteoporosis.

Craniofacial features in osteogenesis imperfecta: A cephalometric study

Osteogenesis imperfecta (OI) is a heterogeneous group of connective tissue diseases that mainly manifest as bone fragility and skeletal deformity. In most families it segregates as a dominant trait and results from mutations in type I collagen genes. In this study we analyzed the size and form of the bony structures in heads of 59 consecutive patients with OI types I, III, or IV (Sillence classification), using lateral radiographs. Paired controls were matched for gender and age. The purpose was to obtain baseline information of craniofacial development in OI patients that have not received bisphosphonate treatment. In OI type I we found smaller than normal linear measurements, indicating a general growth deficiency, but no remarkable craniofacial deformity. In OI types III and IV, the growth impairment was pronounced, and the craniofacial form was altered as a result of differential growth deficiency and bending of the skeletal head structures. We found strong support both for an abnormally ventral position of the sella region due to bending of the cranial base, and for a closing mandibular growth rotation. Vertical underdevelopment of the dentoalveolar structures and the condylar process were identified as the main reasons for the relative mandibular prognathism in OI. Despite of the widespread intervention with bisphosphonates, the facial growth impairment will probably remain characteristic for many OI patients, and their orthodontic treatment should be further developed.

Cardiopulmonary fitness and muscle strength in patients with osteogenesis imperfecta type I

OBJECTIVE

To evaluate cardiopulmonary function, muscle strength, and cardiopulmonary fitness (VO 2 peak) in patients with osteogenesis imperfecta (OI).

STUDY DESIGN

In 17 patients with OI type I (mean age 13.3 +/- 3.9 years) cardiopulmonary function was assessed at rest using spirometry, plethysmography, electrocardiography, and echocardiography. Exercise capacity was measured using a maximal exercise test on a bicycle ergometer and an expired gas analysis system. Muscle strength in shoulder abductors, hip flexors, ankle dorsal flexor, and grip strength were measured. All results were compared with reference values.

RESULTS

Cardiopulmonary function at rest was within normal ranges, but when it was compared with normal height for age and sex, vital capacities were reduced. Mean absolute and relative VO 2 peak were respectively -1.17 (+/- 0.67) and -1.41 (+/- 1.52) standard deviations lower compared with reference values ( P < .01). Muscle strength also was significantly reduced in patients with OI, ranging from -1.24 +/- 1.40 to -2.88 +/- 2.67 standard deviations lower compared with reference values.

CONCLUSIONS

In patients with OI type I, no pulmonary or cardiac abnormalities at rest were found. The exercise tolerance and muscle strength were significantly reduced in patients with OI, which might account for their increased levels of fatigue during activities of daily living.

Intravenous pamidronate treatment of children under 36 months of age with osteogenesis imperfecta

INTRODUCTION

Bone mineral density (BMD) and fracture rates in children with osteogenesis imperfecta (OI) have been shown to improve with bisphosphonate therapy. There are limited data available on the efficacy of this therapy in children with OI under the age of 3 years. To examine this, we instituted a prospective clinical trial of intravenous bisphosphonate to study safety, feasibility, and efficacy of this therapy.

MATERIALS AND METHODS

Nine infants and young children with osteogenesis imperfecta (age range 1-35 months) were treated with intravenous pamidronate. Six had type II OI, two had type I, and one had type IV. Pamidronate was administered in cycles of 3 consecutive days. The total duration of therapy ranged from 11 to 29 months (mean 17 months).

RESULTS

During treatment, the mean annualized percent change in total body areal BMD was 25% (range 11-40%). Pamidronate therapy resulted in sustained and significant decreases in serum calcium and bone-specific alkaline phosphatase and in urine calcium/creatinine and NTX/creatinine. Fracture rate in the group decreased from 80 fractures in 111 months before treatment to 25 fractures in 152 months after treatment (P<0.01). Linear growth and weight gain were maintained. Other than fevers in several infants following the initial dose of intravenous bisphosphonate no adverse effects of therapy were noted.

CONCLUSIONS

Our data support that intravenous pamidronate therapy is safe, increases BMD, and reduces fracture rates in very young children with OI. Currently, it would seem to be the best available treatment for these children.

Syndromes with congenital brittle bones

Background

There is no clear definition of osteogenesis imperfecta (OI). The most widely used classification of OI divides the disease in four types, although it has been suggested that there may be at least 12 forms of OI. These forms have been named with numbers, eponyms or descriptive names. Some of these syndromes can actually be considered congenital forms of brittle bones resembling OI (SROI).

Discussion

A review of different syndromes with congenital brittle bones published in the literature is presented. Syndromes are classified in "OI" (those secondary to mutations in the type I pro-collagen genes), and "syndromes resembling OI" (those secondary to mutations other that the type I pro-collagen genes, identified or not). A definition for OI is proposed as a syndrome of congenital brittle bones secondary to mutations in the genes codifying for pro-collagen genes (COL1A1 and COL1A2).

Summary

A debate about the definition of OI and a possible clinical and prognostic classification are warranted.

[Lethal osteogenesis imperfecta. Prenatal diagnosis]

INTRODUCTION

Osteogenesis imparfecta (OI) comprises a group of disorders principally affecting type I collagen, which result in increased bone fragility. Lethal forms are rare and are characterised by micromelia with malformation of the limbs.

CASE REPORT

A prenatal diagnosis of lethal OI was made by ultrasonography at 18 weeks of gestation and therapeutic abortion was indicated.

COMMENTS

Molecular biology and genetic studies offer new possibilities of prenatal diagnosis, but ultrasonography remains the investigation of choice. It confirms the diagnosis by revealing an increase in bone transparency.

Osteogenesis imperfecta

Osteogenesis imperfecta is a genetic disorder of increased bone fragility, low bone mass, and other connective-tissue manifestations. The most frequently used classification outlines four clinical types, which we have expanded to seven distinct types. In most patients the disorder is caused by mutations in one of the two genes encoding collagen type 1, but in some individuals no such mutations are detectable. The most important therapeutic advance is the introduction of bisphosphonate treatment for moderate to severe forms of osteogenesis imperfecta. However, at present, the best treatment regimen and the long-term outcomes of bisphosphonate therapy are unknown. Although this treatment does not constitute a cure, it is an adjunct to physiotherapy, rehabilitation, and orthopaedic care. Gene-based therapy presently remains in the early stages of preclinical research.

Osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a rare congenital disorder of collagen production that results in brittle bones and affects other body systems containing collagen. This article reviews the current body of knowledge about OI and the management of infants with the disorder. Relieving pain, reducing the incidence of new fractures, establishing adequate follow-up, and connecting parents with community resources are the goals of management during the neonatal period. A case study illustrates management and the discharge process.

The interaction between Sillence type and BMD in osteogenesis imperfecta

Clinical studies with bisphosphonates in children with osteogenesis imperfecta (OI) show an increase in BMD and a decrease in fracture rate. Bone strength in children with OI is not only influenced by changes in BMD but also by changes in collagen I structure of the organic bone matrix. Therefore, we studied the interaction between these two factors in a cross-sectional, single center study including 54 children. We assumed that vertebral deformities in OI represent an unbalance between load and bone strength. Body weight was considered to be a well quantifiable load on vertebral bodies. BMD served as a marker, representing the amount of bone tissue available for vertebral load bearing, and the Sillence classification, either type I or III/IV, as a marker representing the quality of the organic bone matrix. Independent associations were observed between the prevalence of vertebral deformities and (1) Sillence type (OR: 5.7, 95%Cl:1.2-26.8), (2) BMD (OR: 0.003, 95%Cl: 0-0.25) and (3) body weight (OR: 1.15, 95%Cl: 1.05-1.25). Regarding the anthropometrical differences among the different types of OI, the BMD/body weight ratio was introduced to evaluate the BMD in relation to body size. Prevalent vertebral deformities were associated with low BMD/body weight ratios (OR: 0.04, 95%Cl: 0.008-0.2) in OI type I, but no association was found in type III/IV. It was concluded that BMD and Sillence type have independent relationships with vertebral deformities. The BMD/body weight ratio correlates with vertebral deformities in children with OI type I. Its meaning in types III/IV needs further research with larger samples because of the relatively high prevalence of vertebral deformities in this group.

[Updates in osteogenesis imperfecta]

Osteogenesis Imperfecta, a heterogenous group of inherited disorders, is characterized by both bone fragility and low bone mass. Since the Sillence classification of the disease, significant progress has been made in understanding the molecular, histological and genetical pathogenesis of the disease, and it led to expanded nosology. The multidisciplinary approach including rehabilitation, medications and surgery, may significantly improve the quality of life and prolong life expectancy.

Hypercalciuria in Osteogenesis Imperfecta Type I

BACKGROUND

In Osteogenesis Imperfecta severity of disease and reduced physical activity have been considered the main factors contributing to hypercalciuria; however, its pathogenesis in Osteogenesis Imperfecta Type I, in which mobility is normal, is still unclear.

PATIENT, METHODS AND RESULTS

We describe a patient with Osteogenesis Imperfecta Type I and hypercalciuria, in whom measurement of calcium intake, plasma 1 - 25(OH) (2) Vitamin D, fasting calciuria and tubular proteinuria led us to exclude an absorptive or renal component in the pathogenesis of hypercalciuria.

CONCLUSIONS

We believe that hypercalciuria is determined by bone disease in Osteogenesis Imperfecta Type I. This condition should be added to the causes of normocalcemic hypercalciuria in children and the mildest forms should be differentiated from Idiopathic Hypercalciuria.

Osteogenesis imperfecta--clinical and molecular diversity

Osteogenesis imperfecta is a heritable disorder of bone formation resulting in low bone mass and a propensity to fracture. It exhibits a broad range of clinical severity, ranging from multiple fracturing in utero and perinatal death to normal adult stature and a low fracture incidence. The disorder is currently classified into seven types based on differences in clinical presentation and bone architecture. Mutation in one of the type I collagen genes is commonly associated with osteogenesis imperfecta, but is not a prerequisite for the diagnosis. Indeed, the newer forms of osteogenesis imperfecta (types V, VI and VII) are not associated with type I collagen gene defects. Amongst the type I collagen gene mutations that can occur, missense base substitutions involving glycine codons in the exons encoding the central triple-helix forming domain predominate. Such mutations can occur in all the classical forms of osteogenesis imperfecta (types I-IV), but genotype/phenotype correlations are complex and often unpredictable. Treatment of osteogenesis imperfecta by bisphosphonate therapy can improve bone mass in all types of the disorder, and while not being a cure for the disorder does improve the quality of life of the patient.

Assessment of dysplastic dentin in osteogenesis imperfecta and dentinogenesis imperfecta

Two semiquantitative scoring systems, Clinical Radiographic Score (CRS) and Dysplastic Dentin Score (DDS), were introduced for analyzing degree of dysplastic manifestations in dentin. The utility of both systems was demonstrated in a large material of teeth from patients with dentinogenesis imperfecta (DI) and osteogenesis imperfecta (OI). Twenty teeth from healthy controls, 81 teeth from 40 patients with OI, and 18 teeth with DI without OI (DI type II) were examined. The degree of dysplasia was correlated with type and form of OI and type of DI. The median DDS did not differ between DI associated with OI (DI type I) and DI type II. DDS in OI patients without clinical signs of DI was above that of control teeth. Both circumpulpal and mantle dentin showed increased DDS, although circumpulpal dentin was more severely affected. The median DDS was highest for the most severe type of non-lethal OI (type III). DDS increased significantly with form (severity) of OI. A significant association between DDS and CRS was found, although diagnosis of DI in less severe cases was not possible based on radiographic or clinical signs alone. Thus, the DDS system proved valuable when the CRS system based on radiographic/clinical manifestations failed, the most significant finding being subclinical histological manifestations of DI in patients with OI but without clinical or radiographic signs of DI. These subtle dysplastic changes are most likely an expression of genetic disturbances associated with OI and should not be diagnosed as DI, but rather be termed histologic manifestations of dysplastic dentin associated with OI.

Significance of histopathologic examination in the diagnosis of dentin defects associated with type IV osteogenesis imperfecta: two case reports

Two cases of type IV osteogenesis imperfecta, which is divided into subtypes A and B on the basis of the absence or the presence of dental alterations, respectively, are examined with respect to their dental features clinically, radiographically, and histopathologically. There were no characteristic dental abnormalities noted on the clinical and radiographic examination. However, the histopathologic examination with both light and electron microscopy disclosed characteristic dentin defects such as unevenly calcified matrixes, irregular tubular patterns, obliterated dentinal tubules, and cellular inclusions in the circumpulpal dentin of primary teeth. As a result, the patients were diagnosed as having osteogenesis imperfecta type IVB, although the clinical dental alterations were scarcely apparent. These findings indicate the importance of histopathologic examination with light and transmission electron microscopy for accurate diagnosis of osteogenesis imperfecta.