Sillence Type Research Articles

Fracture in long bones stabilised by telescopic intramedullary rods in patients with osteogenesis imperfecta

We investigated the fracture-free survival of long bones stabilised by a telescopic intramedullary rod (TIMR) in patients with osteogenesis imperfecta with respect to the remodelling status of fracture or osteotomy sites and TIMR regions, in order to identify risk factors for fracture. A total of 44 femora and 28 tibiae in 25 patients with a mean age of 5.0 years (1.9 to 10.5) at presentation were studied. There were six patients with Sillence type I, five with type III, 13 with type IV and one with type V osteogenesis imperfecta. All received bisphosphonate treatment at the same stage during the mean follow-up of 7.3 years (0.5 to 18.1). The fracture-free survival was estimated at 6.2 years (95% confidence interval 5.1 to 7.3) by Kaplan-Meier analysis. More than half the fracture or osteotomy sites remained in a less-remodelled state at the latest follow-up or time of fracture. Of the 33 fractures, 29 (87.9%) occurred in long bones containing a less-remodelled site, and these fractures were located at this site. The relative fracture risk at the rod tip was significantly greater than in any other TIMR region (p < 0.001), and this was higher in bone segments having a less-remodelled site. This study shows a persistent fracture risk in TIMR-stabilised long bones, especially at less-remodelled fracture or osteotomy sites and at the rod tip.

Vitamin D Status in Pediatric Patients with Osteogenesis Imperfecta

Osteogenesis Imperfecta (OI) is a heterogeneous genetic disorder causing skeletal fragility. Although there is increasing awareness about the important role of vitamin D in pediatric bone health, specific data regarding vitamin D status are limited and sometimes unavailable in children with musculoskeletal disorders, such as OI. In this study, we aimed to examine the prevalence of vitamin D deficiency, insufficiency and sufficiency in children with OI. We used a retrospective cohort (case-only) study of 61 children diagnosed with OI. The study variables were analyzed using descriptive statistics. 25-hydroxyvitamin D serum levels less than 20 ng/ml were considered deficient, levels between 20–32 ng/ml were considered insufficient, and levels more than 32 ng/ml were considered sufficient. Sixty one patients (31 boys, 30 girls) were classified according to Sillence type (type I, n = 31; type III, n = 14; and type IV, n = 16). Overall, vitamin D insufficiency and deficiency were identified in approximately half of the patients (50.9%). Vitamin D sufficiency was observed in the majority of infants and toddlers from birth to 3 years (n=13, 56.5%) and in children aged 4–10 years (n=12, 57.1%). A minority of children over the age of 10 were vitamin D sufficient (n=5, 29.4%). The majority of Caucasian patients (n=26, 54.2%) were vitamin D sufficient. Sufficient vitamin D levels were more prevalent among type I OI patients (n =19, 61.3%). Type III patients were found to have an equal prevalence of vitamin D insufficiency (n=6, 42.9%) and sufficiency (n=6, 42.9%). Vitamin D insufficiency was most prevalent in type IV (n=8, 50). Patients with an elevated BMI had a higher prevalence of vitamin D insufficiency (n=4, 57.1%). Further studies are recommended to clarify the relationship between vitamin D serum level and BMI in OI patients.

PPIB Mutations Cause Severe Osteogenesis Imperfecta

Deficiency of cartilage-associated protein (CRTAP) or prolyl 3-hydroxylase 1(P3H1) has been reported in autosomal-recessive lethal or severe osteogenesis imperfecta (OI). CRTAP, P3H1, and cyclophilin B (CyPB) form an intracellular collagen-modifying complex that 3-hydroxylates proline at position 986 (P986) in the alpha1 chains of collagen type I. This 3-prolyl hydroxylation is decreased in patients with CRTAP and P3H1 deficiency. It was suspected that mutations in the PPIB gene encoding CyPB would also cause OI with decreased collagen 3-prolyl hydroxylation. To our knowledge we present the first two families with recessive OI caused by PPIB gene mutations. The clinical phenotype is compatible with OI Sillence type II-B/III as seen with COL1A1/2, CRTAP, and LEPRE1 mutations. The percentage of 3-hydroxylated P986 residues in patients with PPIB mutations is decreased in comparison to normal, but it is higher than in patients with CRTAP and LEPRE1 mutations. This result and the fact that CyPB is demonstrable independent of CRTAP and P3H1, along with reported decreased 3-prolyl hydroxylation due to deficiency of CRTAP lacking the catalytic hydroxylation domain and the known function of CyPB as a cis-trans isomerase, suggest that recessive OI is caused by a dysfunctional P3H1/CRTAP/CyPB complex rather than by the lack of 3-prolyl hydroxylation of a single proline residue in the alpha1 chains of collagen type I.

Correlation of Scoliotic Curvature With Z-Score Bone Mineral Density and Body Mass Index in Patients With Osteogenesis Imperfecta

A cross-sectional radiographic and clinical study of patients with osteogenesis imperfecta (OI). To determine demographic, anthropometric, and radiographic parameters that correlate with development of scoliosis in patients with OI. Despite the relatively high prevalence of scoliosis in patients with OI and its clinical significance, little is known about demographic and anthropometric parameters that correlate with the development of scoliosis. Clinical records and spinal radiographs of 19 OI patients were reviewed. There were 5 male and 14 female patients with an average age of 14.2 years (range, 4-20 years). Seven patients were Sillence Type I and 12 patients were Type III. The Cobb angle of scoliosis was analyzed for correlations with age, body mass index (BMI), physical capability, leg-length discrepancy, Z-score bone mineral density (BMD) in the lumbar spine, thoracic kyphosis angle, and lumbar lordosis angle by using Pearson's correlation method. A probability of less than 0.05 was considered statistically significant. The average Cobb angle of scoliosis was 25.2 degrees (range, 5 degrees-108 degrees) including 6 patients with an angle of > or = 30 degrees. Five of these 6 patients were Sillence Type III. Statistical analysis showed a significant positive correlation between the extent of scoliosis and BMI, as well as leg-length discrepancy. There was an inverse correlation between the extent of scoliotic curvature and the Z-score BMD as well as the thoracic kyphosis angle. The correlation of scoliosis with the Z-score BMD and BMI supports the pathology of scoliosis based on vertebral fragility. Proper management of BMD and BMI may have therapeutic value in delaying the progression of scoliosis in patients with osteogenesis imperfecta.

Poster 180: Age of Onset of Scoliosis in Osteogenesis Imperfecta May Be Associated With Sillence Type but Not Body Mass Index

Objective: To determine whether there is an association between body mass index (BMI) earlier in life and/or Sillence type and age of onset of significant scoliosis in children with osteogenesis imperfecta (OI). Design: Retrospective analysis of a convenience sample. Setting: Biomedical research hospital. Participants:86 children with type III and IV OI enrolled in research protocols. 34 subjects met criteria for analysis. Subjects included ambulatory and nonambulatory children. Interventions: Not applicable.

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.

Musculo-skeletal problems associated with pregnancy in women with osteogenesis imperfecta

Having seen a number of women with osteogenesis imperfecta who developed severe back pain during or just after pregnancy, we wished to determine the likelihood of this and other musculoskeletal problems in pregnancy. We interviewed by telephone 100 women with osteogenesis imperfects who had, between them, 213 pregnancies between 1957 and 1998. For each pregnancy we recorded the Sillence type for the osteogenesis imperfecta, the mode of delivery and the musculo-skeletal complications. The most common problem was back pain, which was severe in or after 28 pregnancies (13·1%). There was no identifiable relationship to the type of osteogenesis imperfecta or to the mode of delivery. In many cases the back pain could be related to crush fractures of vertebrae. Other problems identified included spinal deformity, non-vertebral fractures, disc problems and ligament problems. We suggest that it may be appropriate to advise the avoidance of long periods of breast feeding in women with OI, particularly in those who have vertebral fractures.

Multiple Flexion-Stress Vertebral End-Plate Fractures An Osteogenesis Imperfecta Presentation

A 28-year-old woman underwent bone scintigraphy for a 7-day history of severe back pain of sudden onset. Intense linear accumulation of Tc-99m HDP was present in several lower thoracic and lumbar vertebrae without vertebral body deformity. Intense uptake was also present in other thoracic vertebrae with vertebral body changes. X-rays demonstrated osteopenia and dual photon densitometry studies confirmed a significant degree of osteoporosis. Endocrine assessment identified that she and other female members of the family had osteogenesis imperfecta, Sillence type 1. This disorder should be considered in all differential diagnoses of nonobvious traumatic fractures of the vertebrae in healthy young adults.

Osteogenesis Imperfecta as a Differential Diagnosis of Pathologic Burst Fractures of the Spine

A 22-year-old man suffered two noncontiguous burst fractures of the thoracic spine after minor motor vehicular trauma. He was diagnosed with pathologic spinal burst fracture associated with osteogenesis imperfecta Sillence Type 1A. The diagnosis was based on the relatively minor nature of the trauma, clinical characteristics, roentgenograms, and detailed family history. Osteogenesis imperfecta, although rare, should be considered in the differential diagnosis of severe burst fractures of the spine.

A single amino acid deletion in the ?2(I) chain of type I collagen produces osteogenesis imperfecta type III

RNase A protection analysis was used in the search for the cause of a non-lethal osteogenesis imperfecta (OI) phenotype (Sillence type III). Cleavage of the hybrid formed between a normal alpha 2(I) sequence and RNA isolated from the patient indicated the presence of a mismatch. The position of the mismatch was determined and the corresponding area of COL1A2 was amplified using the polymerase chain reaction. Sequencing of cloned amplified DNA revealed the deletion, which was not present in either parent, of the final three bases of exon 19 in one of the patient's two COL1A2 alleles. The deletion results in the loss of amino acid 255 (a valine encoded by the last codon of exon 19) of the triple helical region of half of the alpha 2(I) collagen chains but does not disrupt the splicing of the heterogeneous nuclear RNA (hnRNA). This provides further evidence that OI type III may result from autosomal dominant mutations rather than only from autosomal recessive mutations as had previously been believed.

Non-invasive prenatal diagnosis of osteogenesis imperfecta.

The main mode of non-invasive prenatal diagnosis of osteogenesis imperfecta (OI) is fetal imaging, either by radiography or detailed ultrasonography. Radiography is more of historical interest and ultrasonography is in practice virtually exclusively used for non-invasive second trimester diagnosis of OI. Both methods have also been reported later in pregnancy when diagnosis allows the most appropriate method of delivery to be planned. For example, a caesarean section can be avoided if the fetus is shown to have a form of OI associated with limited survival. Ultrasonography is useful mainly for prenatal diagnosis of the severe forms of OI, especially the perinatally lethal forms (Sillence type II) and to a lesser extent for the severe progressively deforming forms (Sillence types III and III/IV). For the milder varieties of OI (Sillence types I and IV), many cases will be missed by scans. Invasive methods of prenatal diagnosis of OI (principally chorion villous sampling) are used for families with the milder dominant forms of OI and in severe forms of OI in which the actual biochemical or molecular defect in type I collagen is known. Many cases of type II OI and a few of type III have now been reported which were detected by scans before 20 weeks gestation, the earliest being at 15 weeks, for type IIA OI. These include cases not only at genetic risk but also sporadic cases in which scans were done either routinely or for obstetric indications. The ultrasonic abnormalities which are found include reduced echogenicity, multiple fractures, and deformity of the long bones, ribs and skull.(ABSTRACT TRUNCATED AT 250 WORDS)

The growth hormone and somatomedin axis in short children with osteogenesis imperfecta.

Growth deficiency is a cardinal feature of severe osteogenesis imperfecta (OI) and a frequent feature of mild to moderate forms of this disease. We have investigated the status of hormones related to growth in 22 short prepubertal children, 13 males and 9 females, with various types of OI. Ten children had Sillence type III OI, 10 had type IV, and 2 had type I. Evaluation included GRH stimulation, three standard GH provocative tests (arginine-insulin tolerance test, L-dopa), 24-h sampling for measurement of unstimulated GH secretion and a somatomedin-C generation test. None of these children had GH deficiency by standard criteria. We found that 9 OI children had decreased responsiveness to GRH, similar to the GRH response of GH-deficient children. Overall, however, mean 24-h GH values and mean peak GH response to provocative agents of OI children were within the normal range. In the somatomedin generation test, the OI children as a group showed a blunted response, with 13 of 22 having less than a 2-fold stimulation of somatomedin-C by GH. This suggested resistance of the liver and other somatomedin-C secreting tissues to GH. The group with blunted insulin-like growth factor-I response did not correlate significantly with the group with decreased GRH response. To investigate the responsiveness of OI bone to growth stimulation, six OI children with less than average integrated GH secretion were enrolled in a pilot study in which one child received exogenous GH and six received clonidine for at least 6 months. The child treated with exogenous GH and three of six treated with clonidine experienced at least a 4.7 cm/yr increase over their pretreatment growth rates. Growth response could not be predicted from baseline studies. We conclude that abnormalities of the GH-somatomedin axis exist in some children with OI. Administration of GH or clonidine may augment growth rates in OI children; however, the effect of these agents on final stature is unknown.

Recurrence risks and prognosis in severe sporadic osteogenesis imperfecta.

A study was carried out in the United Kingdom of patients with severe osteogenesis imperfecta (OI), born with fractures to normal parents, in order to determine recurrence risks. A total of 105 cases from 98 families survived the perinatal period and 60 cases from 57 families were stillborn or died during the first week of life. The majority of the perinatal survivors correspond to the overlapping group of Sillence type III and sporadic type IV OI. In 40 of these, the radiograph at birth was available and in 37 it showed a characteristic appearance similar to that described previously for type III OI. The other three cases had radiological type IIB OI at birth and died before 26 months of age. The patients with perinatally lethal OI were subdivided on radiological appearance into Sillence type IIA (30 cases, described in the previous paper), type IIB (12 cases from 11 families), and type IIC (three cases from three families), and in five cases from three families the radiological appearance was the same as that of the 37 perinatal survivors described above. Ten cases from 10 families were not classified because their radiographs were unavailable. To analyse the empirical recurrence risks, patients were grouped according to radiological appearance at birth. Those with a type III-like pattern numbered 42 cases and they were grouped with the other cases of severe deforming OI who survived the perinatal period, for whom no x ray at birth was available, making a total of 107 cases. Taking one affected child per family as the proband, there were 98 probands. They had 146 sibs, of whom 10 were affected, giving an empirical recurrence risk of 6.9%. This is consistent with the disease arising as a new dominant mutation in about three quarters of families and as a recessive in about one quarter in this heterogeneous group. It is reasonable to give a recurrence risk of up to 25% in cases with parental consanguinity and a risk of 4.4% in cases with unrelated parents. Fifteen patients (14 probands) with Sillence type IIB OI had 13 sibs, one affected, giving an empirical recurrence risk of 7.7%. The parents were consanguineous in three families and the evidence for autosomal recessive inheritance for the majority in this group is probably stronger. The three patients with type IIC OI had three healthy sibs and the 10 unclassifiable perinatally lethal cases had 22 sibs, all normal. The radiological appearance at birth predicts prognosis to some extent; essentially, the better the bone morphology and mineralisation the longer the survival.

Risk of dominant mutation in older fathers: evidence from osteogenesis imperfecta.

The mean paternal age at birth of 80 presumed mutant cases of dominant osteogenesis imperfecta (OI) was significantly higher than that of population controls and remained so after adjusting for maternal age. There was also an increase in mean maternal age (not significant) which disappeared after adjusting for paternal age. No significant increase in maternal or paternal age was found in cases having OI either of a dominant type with an affected parent or of a type (Sillence type III) usually regarded as recessive. We conclude that, as in certain other dominant conditions, the risk of mutant OI increases with paternal age. However, the rate of increase of risk with paternal age appears to be considerably lower than, for example, in achondroplasia. The overall risk of fresh dominant mutation in older fathers may therefore be lower than has previously been suggested.

Collagen genes and proteins in osteogenesis imperfecta.

Type I collagen is a heteropolymer of alpha 1(I) and alpha 2(I) chains, each of which is a separate product of genes localised to chromosomes 17 and 7 respectively. Molecular defects of type I collagen produce a group of inherited disorders of connective tissue primarily affecting bones, which are easily broken and collagen depleted (osteogenesis imperfecta). Sillence classifies these diseases into four groups, two of which are autosomal dominant and relatively mild, the others being either genetic lethals or responsible for very severe progressive disease. Here we describe two specific molecular abnormalities of type I collagen. One, a cysteine substitution in alpha 1(I) collagen, causes a mild Sillence type I disease, the other, a four base deletion in the C terminal extension of alpha 2(I) collagen, causes progressive Sillence type III disease in the homozygously affected patient and mild premature osteoporosis in his clinically symptomless parents. We have briefly reviewed a variety of other similar mutations causing various OI syndromes, which are tabulated, including various helical and non-helical deletions and a variety of structural protein changes. Several restriction fragment length polymorphisms for alpha 2(I) and alpha 1(II) collagens have also been described, and 5' EcoRI and 3' MspI polymorphisms for alpha 2(I) collagen segregate with Sillence type IV OI.

Reduced strength of skin in osteogenesis imperfecta.

The biochemical properties and ratio collagen type I/type III of skin biopsies from nine patients with osteogenesis imperfecta and nine age- and sex-matched controls were studied. Four of six patients with osteogenesis imperfecta Sillence type I had pronounced reductions in skin tensile strength, decreased ratios of collagen type I/type III, primarily accomplished by reduced amounts of collagen type I, moderate or no disability. The three patients with osteogenesis imperfecta Sillence type III had severe skeletal deformities, but normal skin tensile strength, and ratios of collagen type I/type III within the normal range. These observations may be explained as resulting from various structural defects in the type I collagen of patients with osteogenesis imperfecta.

Exclusion of the alpha 1(II) cartilage collagen gene as the mutant locus in type IA osteogenesis imperfecta.

Using two restriction site polymorphisms within the structural gene coding for human type II collagen we have examined the segregation of this gene in three pedigrees with dominantly inherited osteogenesis imperfecta (Sillence type IA). We have demonstrated that the gene does not segregate with clinical expression of the disease and cannot, therefore, contain the mutation responsible for osteogenesis imperfecta in these families.

Heterogeneity of osteogenesis imperfecta type I.

We have studied 166 patients from 71 families with Sillence type I osteogenesis imperfecta (dominant inheritance and blue sclerae). We confirm earlier findings that there are two subgroups, those with and those without dentinogenesis imperfecta; each family can be allocated to one or other group. Our confidence that the two groups represent distinct disorders is increased by finding that the patients with dentinogenesis imperfecta differ not only in their dental characteristics but also in other clinical features. They have a more severe disease with a greater fracture rate and a greater likelihood of growth impairment.