Bone fragility and osteoporosis in children and young adults

Osteoporosis is a metabolic bone disorder which increases fragility fracture risk. Elderly individuals, especially postmenopausal women, are particularly susceptible to osteoporosis. Although rare, osteoporosis in children and young adults is becoming increasingly evident, highlighting the need for timely diagnosis, management and follow-up. Early-onset osteoporosis is defined as the presence of a low BMD (Z-score of ≤ -2.0 in individuals aged < 20 years; T-score of ≤ -2.5 in those aged between 20 to 50 years) accompanied by a clinically significant fracture history, or the presence of low-energy vertebral compression fractures even in the absence of osteoporosis. Affected children and young adults should undergo a thorough diagnostic workup, including collection of clinical history, radiography, biochemical investigation and possibly bone biopsy. Once secondary factors and comorbidities are excluded, genetic testing should be considered to determine the possibility of an underlying monogenic cause. Defects in genes related to type I collagen biosynthesis are the commonest contributors of primary osteoporosis, followed by loss-of-function variants in genes encoding key regulatory proteins of canonical WNT signalling (specifically LRP5 and WNT1), the actin-binding plastin-3 protein (encoded by PLS3) resulting in X-linked osteoporosis, and the more recent sphingomyelin synthase 2 (encoded by SGMS2) which is critical for signal transduction affecting sphingomyelin metabolism. Despite these discoveries, genetic causes and underlying mechanisms in early-onset osteoporosis remain largely unknown, and if no causal gene is identified, early-onset osteoporosis is deemed idiopathic. This calls for further research to unravel the molecular mechanisms driving early-onset osteoporosis that consequently will aid in patient management and individualised targeted therapy.

A Novel IFITM5 Variant Associated with Phenotype of Osteoporosis with Calvarial Doughnut Lesions: A Case Report

Osteogenesis imperfecta (OI) and other decreased bone density disorders comprise a heterogeneous group of heritable diseases with skeletal fragility. Recently, it was discovered that mutations in SGMS2, encoding sphingomyelin synthetase 2, result in aberrant sphingomyelin metabolism and lead to a novel form of OI termed osteoporosis with calvarial doughnut lesions (OP-CDL) with moderate to severe skeletal fragility and variable cranial hyperostotic lesions. This study describes a Japanese family with the skeletal phenotype of OP-CDL. The affected individuals have moderately severe, childhood-onset skeletal fragility with multiple long-bone fractures, scoliosis and bone deformities. In addition, they exhibit multiple CDLs or calvarial bumps with central radiolucency and peripheral radiopacity. However, SGMS2 sequencing was normal. Instead, whole-exome sequencing identified a novel IFITM5 missense mutation c.143A>G (p.N48S) (classified as a VUS by ACMG). IFITM5 encodes an osteoblast-restricted protein BRIL and a recurrent c.-14C>T mutation in its 5' UTR region results in OI type V, a distinctive subtype of OI associated with hyperplastic callus formation and ossification of the interosseous membranes. The patients described here have a phenotype clearly different from OI type V and with hyperostotic cranial lesions, feature previously unreported in association with IFITM5. Our findings expand the genetic spectrum of OP-CDL, indicate diverse phenotypic consequences of pathogenic IFITM5 variants, and imply an important role for BRIL in cranial skeletogenesis.

Defective WNT signaling may protect from articular cartilage deterioration - a quantitative MRI study on subjects with a heterozygous WNT1 mutation

OBJECTIVE

WNT signaling is of key importance in chondrogenesis and defective WNT signaling may contribute to the pathogenesis of osteoarthritis and other cartilage diseases. Biochemical composition of articular cartilage in patients with aberrant WNT signaling has not been studied. Our objective was to assess the knee articular cartilage in WNT1 mutation-positive individuals using a 3.0T MRI unit to measure cartilage thickness, relaxation times, and texture features.

DESIGN

Cohort comprised mutation-positive (N = 13; age 17-76 years) and mutation-negative (N = 13; 16-77 years) subjects from two Finnish families with autosomal dominant WNT1 osteoporosis due to a heterozygous missense mutation c.652T>G (p.C218G) in WNT1. All subjects were imaged with a 3.0T MRI unit and assessed for cartilage thickness, T2 and T1ρ relaxation times, and T2 texture features contrast, dissimilarity and homogeneity of T2 relaxation time maps in six regions of interest (ROIs) in the tibiofemoral cartilage.

RESULTS

All three texture features showed opposing trends with age between the groups in the medial tibiofemoral cartilage (P = 0.020-0.085 for the difference of the regression coefficients), the mutation-positive individuals showing signs of cartilage preservation. No significant differences were observed in the lateral tibiofemoral cartilage. Cartilage thickness and means of T2 relaxation time did not differ between groups. Means of T1ρ relaxation time were significantly different in one ROI but the regression analysis displayed no differences.

CONCLUSIONS

Our results show less age-related cartilage deterioration in the WNT1 mutation-positive than the mutation-negative subjects. This suggests, that the WNT1 mutation may alter cartilage turnover and even have a potential cartilage-preserving effect.

Defective WNT signaling associates with bone marrow fibrosis-a cross-sectional cohort study in a family with WNT1 osteoporosis

This study explores bone marrow function in patients with defective WNT1 signaling. Bone marrow samples showed increased reticulin and altered granulopoiesis while overall hematopoiesis was normal. Findings did not associate with severity of osteoporosis. These observations provide new insight into the role of WNT signaling in bone marrow homeostasis.

INTRODUCTION

WNT signaling regulates bone homeostasis and survival and self-renewal of hematopoietic stem cells. Aberrant activation may lead to osteoporosis and bone marrow pathology. We aimed to explore bone marrow findings in a large family with early-onset osteoporosis due to a heterozygous WNT1 mutation.

METHODS

We analyzed peripheral blood samples, and bone marrow aspirates and biopsies from 10 subjects with WNT1 mutation p.C218G. One subject was previously diagnosed with idiopathic myelofibrosis and others had no previously diagnosed hematologic disorders. The findings were correlated with the skeletal phenotype, as evaluated by number of peripheral and spinal fractures and bone mineral density.

RESULTS

Peripheral blood samples showed no abnormalities in cell counts, morphology or distributions but mild increase in platelet count. Bone marrow aspirates (from 8/10 subjects) showed mild decrease in bone marrow iron storages in 6 and variation in cell distributions in 5 subjects. Bone marrow biopsies (from 6/10 subjects) showed increased bone marrow reticulin (grade MF-2 in the myelofibrosis subject and grade MF-1 in 4 others), and an increase in overall, and a shift towards early-phase, granulopoiesis. The bone marrow findings did not associate with the severity of skeletal phenotype.

CONCLUSIONS

Defective WNT signaling associates with a mild increase in bone marrow reticulin and may predispose to myelofibrosis, while overall hematopoiesis and peripheral blood values are unaltered in individuals with a WNT1 mutation. In this family with WNT1 osteoporosis, bone marrow findings were not related to the severity of osteoporosis.

PLS3 sequencing in childhood-onset primary osteoporosis identifies two novel disease-causing variants

Altogether 95 children with primary bone fragility were screened for variants in PLS3, the gene underlying X-linked osteoporosis. Two children with multiple peripheral and spinal fractures and low BMD had novel disease-causing PLS3 variants. Children with milder phenotypes had no pathogenic variants. PLS3 screening is indicated in childhood-onset primary osteoporosis.

INTRODUCTION

The study aimed to determine the role of pathogenic PLS3 variants in children's bone fragility and to elucidate the associated phenotypic features.

METHODS

Two cohorts of children with bone fragility were screened for variants in PLS3, the gene underlying X-linked osteoporosis. Cohort I comprised 31 patients with childhood-onset primary osteoporosis of unknown etiology. Cohort II comprised 64 children who had sustained multiple fractures but were otherwise healthy. Clinical and radiological data were reviewed. Peripheral blood DNA was Sanger sequenced for coding exons and flanking intronic regions of PLS3.

RESULTS

In two patients of cohort I, where other common genetic causes had been excluded, we identified two novel disease-causing PLS3 variants. Patient 1 was a male with bilateral femoral fractures at 10 years, low BMD (Z-score -4.1; 18 years), and multiple vertebral compression fractures. He had a novel nonsense variant in PLS3. Patient 2 was a girl with multiple long bone and vertebral fractures and low BMD (Z-score -6.6 at 6 years). She had a de novo missense variant in PLS3; whole exome sequencing and array-CGH identified no other genetic causes. Iliac crest bone biopsies confirmed low-turnover osteoporosis in both patients. In cohort II, no pathogenic PLS3 variants were identified in any of the subjects.

CONCLUSIONS

Two novel disease-causing variants in PLS3 were identified in a boy and a girl with multiple peripheral and spinal fractures and very low BMD while no pathogenic variants were identified in children with less severe skeletal fragility. PLS3 screening is warranted in male and female patients with childhood-onset primary osteoporosis.

Abnormal Proteoglycan Synthesis Due to Gene Defects Causes Skeletal Diseases with Overlapping Phenotypes

In recent years, massively parallel sequencing technologies have helped us to identify novel disease genes and solve the mysteries behind rare diseases. Today, we know that some diseases with many overlapping and distinct clinical features, as presented in this review, can be caused by mutations in genes that encode enzymes playing crucial roles at different steps of the exact same pathway. In this review, we exclusively focused on 5 genes - XYLT1, XYLT2, B4GALT7, B3GALT6, and B3GAT3 - that encode enzymes involved in the biosynthesis of the common tetrasaccharide linker region of proteoglycans and review the associated diseases, also referred to as linkeropathies, by summarizing the cases reported in literature. Since proteoglycans are essential macromolecules in development, signaling and homeostasis of many tissues and organs, mutations in these genes can affect many organs; including bone, cartilage, eyes, ears, heart, and skin. Short stature, developmental delay, facial dysmorphism, and skeletal dysplasias are some of the common features observed in patients with mutations in these genes. Among these genes, XYLT2 mutations cause a relatively distinct phenotype, the so-called spondyloocular syndrome, which is characterized by clinical presentation of a very severe childhood-onset primary osteoporosis, cataract, and hearing impairment. The full phenotype spectrum of diseases mentioned here is likely to expand with additional clinical reports and further molecular studies.

Body composition and adipokines in patients with juvenile idiopathic arthritis and systemic glucocorticoids

OBJECTIVES

The aim of this cross-sectional study was to explore body composition, and the relationship of serum adipokines with bone mass and disease activity, in a cohort of JIA patients with at least three months' exposure to systemic glucocorticoids (GC).

METHODS

Fifty patients with JIA (34 girls, median age 12.4 years and disease duration 6.3 years) and 88 controls matched for gender and age participated in this study. Bone mineral content (BMC) and areal bone mineral density (BMD) of the lumbar spine and whole body, as well as body composition were assessed with dual-energy x-ray absorptiometry. Fasting serum leptin and adiponectin were measured.

RESULTS

Fat and lean mass were similar between patients and controls, but patients had slightly decreased BMD Z-scores. Serum leptin and adiponectin concentrations were similar. Disease activity was low, and no correlation with adipokines was observed. Patients with bone age-corrected lumbar spine BMD Z-score ≤-1.0 ("low BMD") did not show alterations in body composition, GC exposure or current disease activity, but had decreased BMC-to-lean mass ratio (p<0.001) and tendency for increased serum leptin (p=0.064). However, no association of leptin with BMD in multivariate analysis existed in patients or controls. An inverse association between adiponectin and whole body BMD was observed in both groups.

CONCLUSIONS

Normal body composition was observed in a JIA cohort with low-dose GC exposure. Patients with "low BMD" tended to have increased serum leptin, but leptin did not associate with BMD. In this cohort with low disease activity, no correlation between adipokines and disease activity was present.

Bone Characteristics and Their Determinants in Adolescents and Young Adults with Early-Onset Severe Obesity

Childhood obesity is associated with compromised bone health. We studied bone characteristics and their determinants in obese young adults. The study included 68 subjects with early-onset severe obesity and 73 normal-weight controls. Data on physical activity (PA), diet and smoking were collected. Bone characteristics were measured using peripheral QCT. The obese and control subjects were similar in age (mean 19.6 ± 2.6 years) and height but BMIs differed (39.7 and 22.6 kg/m(2)). A clustering of unhealthy lifestyles was marked: Obese subjects reported less supervised PA in childhood, adolescence and currently (p < 0.03) and were more likely to smoke (p = 0.005), and had a lower healthy eating index (HEI) (p = 0.007) but similar alcohol consumption compared with controls. In obese women, all crude bone characteristics were higher than in controls; in men, the differences were smaller. Associations of lifestyle factors with bone characteristics were tested using partial correlations. Independently of BMI, supervised PA in adolescence and alcohol consumption were related positively to bone characteristics in both groups. HEI associated positively with bone characteristics only in controls, while smoking was a positive determinant of bone characteristics only in obese subjects. The multivariate model showed that the contribution of lifestyle factors to bone characteristics was minimal compared with BMI. Early-onset obesity is accompanied by poor dietary quality, sedentary lifestyle, and more frequent smoking, but the overall contribution of these lifestyle factors to bone strength is limited. Bone strength is more likely to be compromised in men and in unloaded bone sites in subjects with early-onset severe obesity. The impact of obesity-related endocrine changes on bone characteristics need to be evaluated in future studies.

SLC26A2 disease spectrum in Sweden - high frequency of recessive multiple epiphyseal dysplasia (rMED)

Diastrophic dysplasia (DTD) is an autosomal recessive skeletal dysplasia caused by SLC26A2 mutations. Clinical features include short stature, joint contractures, spinal deformities, and cleft palate. SLC26A2 mutations also result in other skeletal dysplasias, including the milder recessive multiple epiphyseal dysplasia (rMED). DTD is overrepresented in Finland and we speculated that this may have influenced the prevalence and spectrum of SLC26A2-related skeletal conditions also in Sweden. We reviewed the patient registry at Department of Clinical Genetics, Karolinska University Hospital, Stockholm to identify subjects with SLC26A2 mutations. Seven patients from six families were identified; clinical data were available for six patients. All but one patient had one or two copies of the Finnish SLC26A2 founder mutation IVS1+2T>C. Arg279Trp mutation was present in compound heterozygous form in five patients with phenotypes consistent with rMED. Their heights ranged from -2.6 to -1.4 standard deviation units below normal mean and radiographic features included generalised epiphyseal dysplasia and double-layered patellae. Two rMED patients had hypoplastic C2 and cervical kyphosis, a severe manifestation previously described only in DTD. Our study confirms a high prevalence of rMED in Sweden and expands the phenotypic manifestations of rMED.

Long-term skeletal consequences of childhood acute lymphoblastic leukemia in adult males: a cohort study

OBJECTIVE

Long-term health sequelae of childhood-onset acute lymphoblastic leukemia (ALL) remain largely unknown. Low bone mineral content (BMC) and bone mineral density (BMD) are recognized complications, but it is unknown whether these persist until adulthood. We evaluated skeletal characteristics and their association with ALL therapy in long-term male ALL survivors.

DESIGN

This cross-sectional cohort study included 49 long-term male ALL survivors and 55 age-matched healthy males.

METHODS

BMD and compression fractures were assessed by dual-energy X-ray absorptiometry; blood biochemistry was obtained for parameters of calcium homeostasis.

RESULTS

The ALL survivors (median age 29 years, range 25-38 years), assessed 10-38 years after ALL diagnosis, had lower lumbar spine (P<0.001), femoral neck (P<0.001), and whole-body (P=0.017) BMD than expected based on normative values. When compared with the controls (median age 30 years, range 24-36 years), the ALL survivors had lower lumbar spine BMC (P=0.014), lower whole-body BMC (P<0.001), and lower whole-body BMD (P<0.001), but the differences were partly explained by differences in height. Altogether, 20% of the ALL survivors had spinal compression fractures, but these were equally prevalent in the controls. Males diagnosed with ALL before age 5 years had significantly lower BMD values. Other recognized risk factors included untreated hypogonadism, vitamin D deficiency, hypophosphatemia, low IGF-binding protein-3, and low physical activity.

CONCLUSIONS

At young adulthood, long-term male ALL survivors have significantly reduced BMC and BMD and a high prevalence of spinal compression fractures. Careful follow-up and active treatment of the recognized risk factors are warranted.

Anti-tumor necrosis factor treatment in cherubism--clinical, radiological and histological findings in two children

Cherubism is a rare and disfiguring genetic disorder with excessive bone resorption and multilocular lesions in the mandible and/or maxilla. The disease-causing gain-of-function mutations in the SH3-binding protein 2 (SH3BP2) gene result in increased myeloid cell responses to macrophage colony stimulating factor and RANK ligand, formation of hyperactive osteoclasts (giant cells), and hyper-reactive macrophages that produce excessive amounts of the inflammatory cytokine tumor necrosis factor α (TNF-α). Recent findings in the cherubism mouse model suggest that TNF-α plays a major role in disease pathogenesis and that removal of TNF-α prevents development of the bone phenotype. We treated two children with cherubism with the TNF-α antagonist adalimumab for approximately 2.5 years and collected extensive clinical, radiological and histological follow-up data during the treatment. Histologically the treatment resulted in a significant reduction in the number of multinucleated giant cells and TNF-α staining positivity in both patients. As evaluated by computed tomography and magnetic resonance imaging, the lesions in Patient 1 showed either moderate enlargement (mandibular symphysis) or remained stable (mandibular rami and body, the maxilla). In Patient 2, the lesions in mandibular symphysis showed enlargement during the first 8 months of treatment, and thereafter the lesions remained unchanged. Bone formation and resorption markers remained unaffected. The treatment was well tolerated. Based on our findings, TNF-α antagonist may decrease the formation of pathogenic giant cells, but does not result in lesion regression or prevent lesion expansion in active cherubism. TNF-α modulator treatment thus does not appear to provide sufficient amelioration for patients suffering from cherubism.

Osteoporosis-pseudoglioma syndrome: three novel mutations in the LRP5 gene and response to bisphosphonate treatment

BACKGROUND/AIMS

Osteoporosis-pseudoglioma (OPPG) syndrome is a rare disorder characterized by congenital or infancy-onset visual loss and severe juvenile osteoporosis. OPPG is caused by homozygous mutations in the low-density lipoprotein receptor-related protein 5 (LRP5) gene. We present three novel homozygous LRP5 mutations found in 3 unrelated Turkish children with consanguineous parents, along with clinical phenotypes and response to treatment with bisphosphonates (bisP).

METHODS/RESULTS

The LRP5 gene was analyzed by direct sequencing after PCR amplification. Mutation screening for LRP5 revealed homozygous nonsense R1002X mutation in the first patient and homozygous missense mutations V336M and G507S in the second and third patient, respectively. The parents were heterozygous for these mutations. The patients' eye symptoms began during the first months of life but the OPPG diagnoses were made based on skeletal deformities and osteopenia after 4 years of age. The patients' bone mineral density Z scores were very low and consistent with osteopenia. All patients were treated with bisP for 3.5-7 years.

CONCLUSION

We report three novel LRP5 mutations in 3 Turkish patients with OPPG. We show that the response of bisP therapy has improved the lumbar spinal bone mineral density Z scores and the patients' quality of life as the bone pains decreased.

Peripheral quantitative computed tomography (pQCT) reveals alterations in the three-dimensional bone structure in children with haemophilia

Children with haemophilia are at risk of suboptimal bone mass accrual and low bone mineral density (BMD). We recently demonstrated that although BMD in Finnish children with haemophilia was within the normal range, their whole body BMD was significantly lower and hypercalciuria more prevalent than in controls. This study sought to determine the bone structure and strength in physically active children with haemophilia. To investigate the underlying mechanisms in this group, we conducted a case-control study to assess bone structure and strength by peripheral quantitative computed tomography (pQCT) at the radius. The study group comprised 29 patients (mean age 12.2 years) and 46 age-matched controls. Children with haemophilia had decreased total BMD Z-score at the distal radius (P ≤ 0.001), but increased cortical bone density at the proximal radius (P ≤ 0.001). Total bone area at the proximal radius was significantly lower in children with haemophilia (P = 0.002), whereas there were no differences in cortical bone area or in polar Strength-Strain Index, a parameter of bone strength, between the patients and controls. Patients with mild to moderate haemophilia and on-demand treatment had inferior bone strength compared to those with moderate to severe haemophilia and prophylaxis. Our findings suggest altered skeletal development in patients with haemophilia in the radius, resulting in smaller bone size and higher cortical bone density. Importantly, bone strength at the radius appears equal to healthy children. Prophylactic treatment seems to have a beneficial effect on bone health.

The effect of oral glucose tolerance test on serum osteocalcin and bone turnover markers in young adults

Osteocalcin (OC) is an osteoblast-derived protein implicated in the regulation of glucose tolerance and energy metabolism. This endocrine function has been suggested to be exerted via its undercarboxylated form, which has been shown to induce expression of adiponectin, insulin, and islet cell proliferation in mice. Furthermore, insulin has recently been shown to regulate the biological activity of OC in bone. Our aim was to explore the association between glucose and bone metabolism by evaluating the effect of a standard 75 g oral glucose tolerance test (OGTT) on serum OC, carboxylated OC (cOC) and bone-turnover markers (BTMs) C terminal telopeptide (βCTX-I) and N terminal propeptide (PINP) of type I collagen and tartrate-resistant acid phosphatase 5b (TRACP5b). Serum samples collected at 0 and at 120 min were analyzed in a cohort of normoglycemic young adults (n = 23, mean age 23.6 years). During OGTT a significant decrease was observed in all BTMs (P < 0.001 for all variables). The median decreases from 0 to 120 min for OC, cOC, βCTX-I, PINP, and TRACP5b were -32.1% (-37.9 to -19.6), -34.4% (-39.8 to -22.2), -61.4% (-68.5 to -53.0), -26.8% (-33.2 to -19.2), and -44.5% (-48.3 to -40.2), respectively. A strong association between the changes in OC and cOC was observed (r = 0.83, P < 0.001). The decrease in PINP was associated with changes in OC, whereas the changes in βCTX-I and TRACP5b were not associated with decreases in OC or cOC. The observed OGTT-induced changes in bone-derived proteins were partially independent of each other and potentially mediated by different mechanisms.

Maternal vitamin D status affects bone growth in early childhood--a prospective cohort study

In this prospective study, 87 children were followed up from birth to 14 months with data on maternal vitamin D status during the pregnancy. Postnatal vitamin D supplementation improved vitamin D status but only partly eliminated the differences in bone variables induced by maternal vitamin D status during the fetal period.

INTRODUCTION

Intrauterine nutritional deficits may have permanent consequences despite improved nutritional status postnatally. We evaluated the role of prenatal and postnatal vitamin D status on bone parameters in early infancy.

METHODS

Eighty-seven children were followed from birth to 14 months. Background data were collected with a questionnaire and a 3-day food record. At 14 months bone variables were measured with peripheral computed tomography (pQCT) from the left tibia. Serum 25-OHD and bone turnover markers were determined. Findings were compared with maternal vitamin D status during pregnancy.

RESULTS

The children were divided into two groups based on vitamin D status during pregnancy. Despite discrepant S-25-OHD at baseline (median 36.3 vs. 52.5 nmol/l, p < 0.001), the values at 14 months were similar (63 vs. 66 nmol/l, p = 0.58) in Low D and High D. Serum 25-OHD increased more in Low D (p < 0.001) despite similar total intake of vitamin D (mean 12.3 μg/day). In Low D, tibial bone mineral content (BMC) was lower at birth but BMC gain was greater (multivariate analysis of variance [MANOVA]; p = 0.032) resulting in similar BMC at 14 months in the two groups. In High D, tibial total bone cross-sectional area was higher at baseline; the difference persisted at 14 months (MANOVA; p = 0.068). Bone mineral density (BMD) and ΔBMD were similar in the two groups.

CONCLUSIONS

Postnatal vitamin D supplementation improved vitamin D status but only partly eliminated the differences in bone variables induced by maternal vitamin D status during the fetal period. Further attention should be paid to improving vitamin D status during pregnancy.

Maternal vitamin D status determines bone variables in the newborn

CONTEXT

Vitamin D regulates 3% of the human genome, including effects on bone health throughout life. Maternal vitamin D status may program neonatal skeletal development. The objective here was to determine the association of mothers' vitamin D status with bone variables of their newborns.

SUBJECTS AND METHODS

In a birth hospital, pregnant women (n = 125) participated in a cross-sectional study with a longitudinal follow-up of the pregnancy. The mean (sd) values for age, body mass index before pregnancy, pregnancy weight gain, and total vitamin D intake in mothers were 31 (4) yr, 23.5 (3.7) kg/m(2), 13.1 (4.3) kg, and 14.3 (5.8) microg, respectively. All newborns were full-term, 99% were appropriate for gestational age, and 53% were boys. Blood samples were collected from mothers during the first trimester and 2 d postpartum and from umbilical cords at birth for analysis of serum 25-hydroxyvitamin D (S-25-OHD), PTH, and bone remodeling markers. Bone variables were measured by pQCT at the 20% site of the newborn tibia on an average of 10 (11) d postpartum. Bone contour was analyzed with a single threshold of 180 mg/mm(3) for the detection of total bone mineral density (BMD), bone mineral content (BMC), and cross-sectional area (CSA).

RESULTS

Mean S-25-OHD was 41.0 (13.6), 45.1 (11.9), and 50.7 (14.9) nmol/liter during the first trimester, postpartum, and in the umbilical cord, respectively. The median value of the individual means for first trimester and the 2-d postpartum S-25-OHD was 42.6 nmol/liter, which was used as cutoff to define two equal-sized groups. Groups are called below median and above median in the text. Newborns below median were heavier (P = 0.05), and 60% were boys. Tibia bone mineral content was 0.047 (95% confidence interval, 0.011-0.082) g/cm higher (P = 0.01), and cross-sectional area was 12.3 (95% confidence interval, 2.0-22.6) mm(2) larger (P = 0.02), but no difference in bone mineral density was observed, above median compared with below median group. These results were adjusted for newborn Z-score birth weight, maternal height, and newborn age at the measurement. A positive, significant correlation was observed between remodeling markers in mothers at different time points and above median group in the cord.

CONCLUSIONS

Although the mean total intake of vitamin D among mothers met current Nordic recommendations, 71% of women and 15% of newborns were vitamin D deficient during the pregnancy. Our results suggest that maternal vitamin D status affects bone mineral accrual during the intrauterine period and influences bone size. More efforts should be made to revise current nutrition recommendations for pregnant women that may have permanent effects on the well-being of children.

Vitamin D status and optimal supplementation in institutionalized adults with intellectual disability

BACKGROUND

Adults with intellectual disability (ID) have several risk factors for osteoporosis. Feeding problems with consequent nutritive deficiencies, and lack of sunshine exposure may lead to vitamin D deficiency. The purpose of this study was to evaluate vitamin D status in adults with ID living in nursing homes and to compare two different means to administer vitamin D in adults with ID.

METHODS

The study included 138 adults (95 males and 43 females) with ID living in nursing homes of Pääjärvi Inter-Municipal Association. Clinical data on the etiology and severity of ID, other illnesses, medications, anthropometry and fractures during the preceding 5 years were collected from medical records. The participants were alternately allocated to receive vitamin D3 either per orally 800 IU daily for 6 months (PO group, n = 72) or as a single intramuscular injection of 150 000 IU (IM group, n = 66). Blood samples were obtained at baseline and at 6 months for parameters of calcium homeostasis, including serum concentrations of 25-hydroxyvitamin D (S-25-OHD) and parathyroid hormone (P-PTH).

RESULTS

At baseline, the mean S-25-OHD was low, 40 nmol/L in the PO group and 41 nmol/L in the IM group. The low vitamin D levels were associated with secondary hyperparathyroidism in 17%. At 6 months the mean S-25-OHD was 82 nmol/L in the PO group (P < 0.001 for the difference from baseline) and 62 nmol/L in the IM group (P < 0.001). P-PTH decreased in both groups: from 51 ng/L to 33 ng/L in the PO group (P < 0.001) and from 54 ng/L to 34 ng/L in the IM group (P < 0.001). With daily dosing (800 IU/day) the recommended level (>80 nmol/L) was attained in 42%, but with intramuscular dose only in 12%. S-25-OHD was >100 nmol/L in 14 participants in the PO group and in one participant in the IM group; these high values were associated with hypercalcemia in two and hyperphosphatemia in six participants. Participants with S-25-OHD >100 nmol/L at 6 months were lighter (51.9 kg vs. 67.5 kg, P = 0.002) and had smaller body mass index than participants with lower S-25-OHD (20.5 kg/m(2) and 24.4 kg/m(2), P = 0.017).

CONCLUSIONS

Vitamin D insufficiency was common in adults with ID living in nursing homes. Both oral and intramuscular administrations of vitamin D3 improved vitamin D status without adverse effects. The treatment response at 6 months was better in the PO group. High-dose intramuscular vitamin D3 injections may be a convenient way to maintain sufficient vitamin D status in adults with ID but further studies are needed to establish the optimal dose and interval as well as subsequent potential health benefits in these patients. Based on this study, vitamin D supplementation with per oral 800 IU/day is recommended to all adults with ID living in nursing homes.

Insufficient energy and nutrient intake in children with motor disability

AIM

Children with motor disabilities are at increased risk of compromised bone health due to impaired weight bearing. Poor nutritional status may be an additional risk factor. The aim of this study was to evaluate energy and nutrient intakes in children with motor disability.

PATIENTS AND METHODS

Fifty-four children with motor disability (cerebral palsy in 59%) were included. Three-day food diaries were collected and analysed. The results were compared with recommended dietary allowances for age and sex.

RESULTS

The median age was 10.9 years. The median energy intake was 76% of the recommendation and <80% in 57% of children. Of the total energy, 17% was from protein, 32% from fat and 50% from carbohydrates. The medians were for calcium intake 142% and for vitamin D intake 76% of the recommendation; serum 25-hydroxy-vitamin D concentrations were low (median 46 nmol/L). Children with low energy intake were shorter and lighter and had more severe motor disability than children with sufficient energy intake.

CONCLUSION

Insufficient energy and nutrient intake is common in children with motor disability. This may have adverse health effects especially when associated with low vitamin D intake. Energy and vitamin D supplements should be considered.

Impaired bone health in adolescents after liver transplantation

Long-term complications related to immunosuppressive medication are an important problem after liver transplantation (OLT). This study was carried out to evaluate the bone health and risk factors for osteoporosis and fractures in 40 pediatric liver transplant recipients. The results of 208 longitudinal bone mineral density (BMD) measurements were analyzed retrospectively. In addition, a dual-energy X-ray absorptiometry was performed to assess the bone mineral content more precisely and to detect subclinical vertebral fractures (VF). The median age of the patients was 14 years and mean postoperative follow-up 7.0 years. The results showed that over half (58%) had lumbar spine (LS) Z-score </=-1.0 and one-fifth (18%) had asymptomatic VF. LS Z-score tended to increase from the first year after OLT, but during puberty the bone mass gain was suboptimal and Z-scores decreased in some subjects. Patients with VF were older at the time of OLT (p = 0.002) and their LS Z-score was lower (p = 0.001). Children transplanted before 10 years of age had less VF (p = 0.004) and higher LS Z-score (p = 0.005) than older patients. In conclusion, adolescent liver recipients are prone to osteoporosis and prevention should be targeted especially to this age group.

High-dose vitamin D supplementation in children with cerebral palsy or neuromuscular disorder

Adequate vitamin D levels are essential for normal skeletal development and mineralization. This is particularly important in children with cerebral palsy or other neuromuscular disorders who are at an increased risk of osteoporosis. The aim of this study was to evaluate the effect of high-dose vitamin D3 supplementation on vitamin D status in 44 disabled children. Vitamin D was administered during school days (1000 IU vitamin D3 per orally five days per week for 10 weeks) to half of the children (N=21) while the others (N=23) continued without supplementation. At baseline the median serum 25-hydroxyvitamin D was 44 nmol/L (range 26-82 nmol/L). The concentration increased significantly during the 10 weeks intervention in the supplemented group (median 56 nmol/L, range 39-88 nmol/L; p=0.012 for the difference from baseline) and decreased in the control group (median 37 nmol/L, range 24-74 nmol/L; p=0.038). No significant changes in any of the other measured parameters were observed. Hypovitaminosis D is prevalent in disabled children. Supplementation with 1000 IU vitamin D3 perorally five days per week results in a significant increase in vitamin D level and is not associated with hypercalcemia or other adverse effects.

Cerebroretinal microangiopathy with calcifications and cysts

BACKGROUND

Extensive cerebral calcifications and leukoencephalopathy have been reported in two rare disorders Coats plus and leukoencephalopathy with calcifications and cysts. In the latter, a progressive formation of parenchymal brain cysts is a special feature, whereas Coats plus is characterized by intrauterine growth retardation, bilateral retinal telangiectasias and exudations (Coats disease), sparse hair, and dysplastic nails without cyst formation.

METHODS

We identified 13 patients, including two pairs of siblings, with extensive cerebral calcifications and leukoencephalopathy. We reviewed clinical, ophthalmologic, radiologic and neuropathologic data of seven deceased patients and studied five patients prospectively.

RESULTS

Eleven patients were small for gestational age; the other symptoms emerged from infancy to adolescence. All patients had neurologic symptoms including seizures, spasticity, dystonia, ataxia, and cognitive decline. Progressive intracerebral calcifications involved deep gray nuclei, brainstem, cerebral and cerebellar white matter, and dentate nuclei and were accompanied by diffuse white matter signal changes and, in five patients, cerebral cysts. Eleven patients had retinal telangiectasias or angiomas. Additional features were skeletal and hematologic abnormalities, intestinal bleeding, and poor growth. Neuropathologic examination showed extensive calcinosis and abnormal small vessels with thickened, hyalinized wall and reduced lumen.

CONCLUSIONS

Our data suggest that Coats plus syndrome and leukoencephalopathy with calcifications and cysts belong to the same spectrum. The primary abnormality seems to be an obliterative cerebral angiopathy involving small vessels, leading to dystrophic calcifications via slow necrosis and finally to formation of cysts and secondary white matter abnormalities.

Bone health in autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED): findings in 25 adults

OBJECTIVE

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is characterized by chronic mucocutaneous candidiasis and autoimmune destruction of endocrine organs. The resulting endocrinopathies and their treatment may impact bone health. The purpose of our study was to assess bone health and its correlates in adult patients with APECED.

PATIENTS AND METHODS

Twenty-five adults (12 males) with APECED were prospectively assessed. Data on their previous medical history were collected from hospital records. Areal bone mineral density (aBMD) for the lumbar spine (L1-L4), femoral neck and whole body as well as volumetric BMD (vBMD) for the lumbar spine (L2-L4) were measured with dual-energy X-ray absorptiometry (DXA).

RESULTS

Mean age was 34 years (range 21-59 years). All patients had 1-4 autoimmune endocrinopathies, the most common being adrenocortical failure (20 patients) and hypoparathyroidism (18 patients). Osteopaenia or osteoporosis was present in 28%. The median (range) aBMD Z-scores were for the lumbar spine -0.3 (-2.3 to +3.3) and for the femoral neck, -0.1 (-2.2 to +2.0). The BMD Z-scores tended to be higher in patients with hypoparathyroidism than in patients with normal parathyroid function (at the lumbar spine +0.4 vs.-1.2, P = 0.016, and at the femoral neck +0.3 vs.-0.4, P = 0.090). Adrenocortical failure had a negative impact on BMD. Six patients had had low-impact fractures and three were diagnosed with compression fractures.

CONCLUSIONS

Despite the complex endocrine problems, the overall prevalence of symptomatic osteoporosis is low in adults treated for APECED. Osteopaenia is frequently observed and warrants follow-up. Treated hypoparathyroidism may have a positive, and adrenocortical failure a negative, impact on bone health.

Scoliosis after solid organ transplantation in children and adolescents

The occurrence of scoliosis in children after solid organ transplantation is not known. A total of 196 children, which is 93% of patients surviving kidney, liver and heart transplantation in our country, participated in a cross-sectional survey. All children were screened for rib hump, and those with clinically significant hump (over 6 degrees ) underwent radiographs of the spine. The occurrence of scoliosis was compared to data obtained from a previously published comparison group. Forty-three (21.9%) of the patients had scoliosis greater than 10 degrees , and 21 (10.7%) of them had curves greater than 20 degrees . The RR (95% CI) for scoliosis needing treatment (over 20 degrees ) was 17.0 (6.75-42.7) in the patients as compared with control population. The occurrence of scoliosis was 17.9% of the kidney, 13.6% of the liver and 51.7% of the heart transplant patients (p < 0.001). In a logistic regression model, heart transplantation (OR (95% CI) 7.27 (2.62-20.2)) and growth hormone treatment (3.98 (1.77-8.94)) were most significant risk factors for scoliosis. The risk of scoliosis is increased in patients with solid organ transplantation. Pediatricians treating these patients should be aware of this increased risk to diagnose early curves and to refer these patients to an orthopedic surgeon.

Skeletal phenotype in patients with Shwachman-Diamond syndrome and mutations in SBDS

Pancreatic exocrine and bone marrow dysfunctions are considered to be universal features of Shwachman-Diamond syndrome (SDS) whereas the associated skeletal dysplasia is variable and not consistently observed. The genetic defect in SDS has recently been identified; causative mutations have been shown in the SBDS gene. The aims of this study were to characterize the nature, frequency, and age-related changes of radiographic skeletal abnormalities in patients with SBDS mutations and to assess genotype-phenotype correlation. Fifteen patients (mean age 9.7 years) with a clinical diagnosis of SDS and documented SBDS gene mutations were included. Review of their skeletal radiographs showed abnormalities in all patients. The skeletal changes were variable, even in patients with identical genotypes. The typical features were (1) delayed appearance of secondary ossification centers, (2) variable widening and irregularity of the metaphyses in early childhood, followed by progressive thickening and irregularity of the growth plates, and (3) generalized osteopenia. There was a tendency towards normalization of the epiphyseal maturation defect and progression of the metaphyseal changes with age. The results suggest that the characteristic skeletal changes are present in all patients with SDS and SBDS mutations, but their severity and localization varies with age. No phenotype-genotype correlation was observed.

Genetic changes in the RNA components of RNase MRP and RNase P in Schmid metaphyseal chondrodysplasia

BACKGROUND

The Schmid type of metaphyseal chondrodysplasia (MCDS) is generally due to mutations in COL10A1 encoding for type X collagen of cartilage.

METHODS

We performed a study on the genes coding for the RNA components of RNase MRP (MRPR) and RNase P (H1RNA) among 20 patients with diagnosis of MCDS and no mutations in COL10A1.

RESULTS

Two patients were found to be homozygous for a base substitution G for A at nucleotide 70 of RMRP, which is the major mutation causing cartilage-hair hypoplasia. No pathogenic mutations were detected in H1RNA.

CONCLUSION

Cartilage-hair hypoplasia diagnosis should be considered in patients with metaphyseal chondrodysplasia even in the absence of any extra-skeletal manifestations if no mutation in COL10A1 can be found and the family history is compatible with autosomal recessive inheritance. Correct diagnosis is important for genetic counselling and for proper follow up of the patients.

Early treatment improves growth and biochemical and radiographic outcome in X-linked hypophosphatemic rickets

X-Linked hypophosphatemic rickets (XLH) is characterized by hypophosphatemia, rickets, and impaired growth. Despite oral phosphate and 1,25-dihydroxyvitamin D(3) treatment, many patients have suboptimal growth and bone healing. The aim of this study was to assess whether age at treatment onset impacts the outcome. Growth data, biochemistry, and radiographs of 19 well-controlled patients with XLH were analyzed retrospectively. Patients were divided into two groups based on the age at treatment onset (group 1, <1.0 yr; group 2, >or=1.0 yr). The median height z-score was higher in group 1 (n = 8) than in group 2 (n = 11) at treatment onset [-0.4 SD score (SDS) vs. -1.7 SDS; P = 0.001], at the end of the first treatment year (-0.7 SDS vs. -1.8 SDS; P = 0.009), throughout childhood (P > 0.05) and until predicted adult height (-0.2 SDS vs. -1.2 SDS; P = 0.06). The degree of hypophosphatemia was similar in both groups, but serum alkaline phosphatase remained higher in group 2 throughout childhood. Radiographic signs of rickets were more marked in group 2, but even patients with early treatment developed significant skeletal changes of rickets. These data suggest that treatment commenced in early infancy results in improved outcome in patients with XLH, but does not completely normalize skeletal development.

Hirschsprung disease associated with severe cartilage-hair hypoplasia

Cartilage-hair hypoplasia is a chondrodysplasia with a high incidence of Hirschsprung disease. This study suggests that Hirschsprung disease is associated especially with severe cartilage-hair hypoplasia: the patients with Hirschsprung disease had severe growth failure and a higher incidence of alopecia, infections, malignancies, and childhood anemia than the patients with cartilage-hair hypoplasia who did not have Hirschsprung disease.

Mutations in the RNA component of RNase MRP cause a pleiotropic human disease, cartilage-hair hypoplasia

The recessively inherited developmental disorder, cartilage-hair hypoplasia (CHH) is highly pleiotropic with manifestations including short stature, defective cellular immunity, and predisposition to several cancers. The endoribonuclease RNase MRP consists of an RNA molecule bound to several proteins. It has at least two functions, namely, cleavage of RNA in mitochondrial DNA synthesis and nucleolar cleaving of pre-rRNA. We describe numerous mutations in the untranslated RMRP gene that cosegregate with the CHH phenotype. Insertion mutations immediately upstream of the coding sequence silence transcription while mutations in the transcribed region do not. The association of protein subunits with RNA appears unaltered. We conclude that mutations in RMRP cause CHH by disrupting a function of RNase MRP RNA that affects multiple organ systems.

Increased mortality in cartilage-hair hypoplasia

BACKGROUND

Cartilage-hair hypoplasia (CHH) is an autosomal recessive chondrodysplasia with severe growth failure and impaired immunity. Impaired immunity may result in increased mortality.

AIMS

To follow a cohort of 120 CHH patients for mortality from 1971 to 1995.

METHODS

The overall and cause specific disease mortality rates in patients with CHH, and the disease mortality rate in 194 parents and 158 non-affected sibs were compared with the national rates.

RESULTS

During follow up seven disease related deaths were observed versus 0.8 expected (standardised mortality ratio 9.3, 95% confidence interval 3.7 to 19). In most cases, the deaths were confined to the younger age groups and associated with defective immunity. The mortality of the parents and the non-affected sibs was similar to that in the general population.

CONCLUSION

The study confirms increased mortality in patients with CHH attributable to defective immunity, especially in children.

Deficiency of humoral immunity in cartilage-hair hypoplasia

OBJECTIVE

Cartilage-hair hypoplasia (CHH), a metaphyseal chondrodysplasia, is usually associated with impaired cellular immunity. This study evaluates humoral immunity in patients with CHH.

METHODS

The concentrations of immunoglobulins G, A, and M (IgG, IgA, and IgM) and IgG subclasses were studied in 20 patients. Data for 5 additional patients with recurrent infections were retrospectively reviewed.

RESULTS

Seven of the prospectively evaluated patients (35%) had defective humoral immunity. Three patients had IgA deficiency. Four patients had IgG2 deficiency, accompanied by IgA deficiency, IgG4 deficiency, or both in 3 patients. IgG4 was low in most patients. Increased infections were usually associated with supranormal IgG and IgG1 and subnormal IgA, IgG2, or IgG4 concentrations. One retrospectively reviewed patient had severe hypogammaglobulinemia, and 3 had multiple IgG subclass deficiencies.

CONCLUSIONS

Humoral immunity is impaired in CHH and contributes to the increased susceptibility to infections.

Anemia in children with cartilage-hair hypoplasia is related to body growth and to the insulin-like growth factor system

Cartilage-hair hypoplasia (CHH) is a metaphyseal chondrodysplasia characterized by severe short-limbed short stature, hypoplastic hair, and defective immunity. The patients also have anemia. As GH may regulate both body growth and erythropoiesis, we used CHH as a clinical model to study their interrelationships. Retrospective analysis of hematological data of 114 patients showed that the severity of the anemia and macrocytosis in CHH varies with age. The anemia was most severe in early childhood. A prospective study of 21 patients with CHH showed that height correlates with hemoglobin (P = 0.006) and mean corpuscular volume of red blood cells (P < 0.0001). The individual hemoglobin levels correlated with the GH parameters [P = 0.035 for insulin-like growth factor I (IGF-I) and P = 0.002 for IGF-binding protein-3], and the mean corpuscular volume of red blood cell values correlated with fetal hemoglobin. Bone marrow cultures obtained from six patients with CHH showed reduced or totally absent erythroid colony formation, which was not influenced by GH or IGF-I in vitro or by GH treatment in vivo. In patients with CHH, we observed an association between erythropoiesis and growth. We conclude that body growth and erythropoiesis share common regulators. One of these is the GH-IGF-I axis; other factors, as not yet identified, may also be important.

Increased incidence of cancer in patients with cartilage-hair hypoplasia

OBJECTIVE

Previous reports have suggested an increased risk of cancer among patients with cartilage-hair hypoplasia (CHH). This study was carried out to further evaluate this risk among patients with CHH and their first-degree relatives.

STUDY DESIGN

One hundred twenty-two patients with CHH were identified through 2 countrywide epidemiologic surveys in 1974 and in 1986. Their parents and nonaffected siblings were identified through the Population Register Center. This cohort underwent follow-up for cancer incidence through the Finnish Cancer Registry to the end of 1995.

RESULTS

A statistically significant excess risk of cancer was seen among the patients with CHH (standardized incidence ratio 6.9, 95% confidence interval 2.3 to 16), which was mainly attributable to non-Hodgkin's lymphoma (standardized incidence ratio 90, 95% confidence interval 18 to 264). In addition, a significant excess risk of basal cell carcinoma was seen (standardized incidence ratio 35, 95% confidence interval 7.2 to 102). The cancer incidence among the siblings or the parents did not differ from the average cancer incidence in the Finnish population.

CONCLUSIONS

This study confirms an increased risk of cancer, especially non-Hodgkin's lymphoma, probably attributable to defective immunity, among patients with CHH.

Susceptibility to infections and in vitro immune functions in cartilage-hair hypoplasia

Cartilage-hair hypoplasia (CHH), an autosomal recessive chondrodysplasia, results in severe growth failure, sparse hair and impaired cellular immunity. Lymphocyte subpopulations and proliferative responsiveness in mitogen stimulation were analysed in 35 patients of whom 31% had an increased incidence of infections the year prior to the evaluation. Of the patients, 57% had a decreased CD4+ cell count which led to a decreased total count of T-lymphocytes in 52% and a subnormal CD4 +/CD8 + cell ratio in 32%. The B-lymphocyte count was usually normal. The natural killer cell count was above reference values in 40% of the patients. The lymphocyte stimulation indices as studied with phytohaemagglutinin , Concanavalin A and pokeweed mitogen were subnormal in 69%, 69% and 83% of the patients, respectively. The numbers of lymphocytes, T-lymphocytes and CD4+ cells, and the pokeweed mitogen stimulation index. but not the other measured parameters, correlated significantly with the proness to infections during the preceding year. However, the correlation was reverse with higher counts in the patients who had had recurring infections. The observed significant correlations may reflect immunological stimuli caused by recurring infections.

CONCLUSION

The presently used parameters of cellular immunity poorly predict the clinical outcome of an individual cartilage-hair hypoplasia patient. All patients, irrespective of their in vitro immunological competence, have to be carefully followed because of possibility of serious infections and malignancies.

Growth in diastrophic dysplasia

OBJECTIVE

To study the growth and its correlates in diastrophic dysplasia (DTD) and to construct standard growth curves for DTD.

METHODS

Growth data of 121 Finnish patients with DTD were collected. Percentile growth curves for height and relative weight were constructed by using interpolated values from individual curves. Pubertal growth, intrafamilial variability, and correlates of adult height were assessed.

RESULTS

The median adult height was 135.7 cm for the male and 129.0 cm for the female subjects. The growth failure was progressive partly because of absent or weak pubertal growth spurt. The severity of the growth failure varied greatly, even among siblings. The final height did not correlate with the midparental height but correlated well with the height at 1.0 and 5.0 years. The relative weight was normal in childhood but increased before puberty; 28% of the adults were overweight. Head circumference was normal.

CONCLUSIONS

DTD interferes profoundly with normal growth and results in progressive growth failure of varying severity. The growth charts should prove useful in following up an individual patient with DTD; they may be used to predict adult height and to evaluate growth-promoting therapies.

Uniparental disomy in cartilage-hair hypoplasia

Cartilage-hair hypoplasia (CHH) is an autosomal recessive disorder that presents with pleiotropic manifestations including impaired skeletal growth and cellular immunity. It is most prevalent among two founder populations, the Old Order Amish in the USA and the Finns. The gene has been localized to 9p13 by linkage analysis and linkage disequilibrium mapping. A statistically significant deficiency of affected members resulting in a lower than expected segregation ratio has been reported in the Amish, but was not found in a previous study in Finnish CHH families. Reduced penetrance was the mechanism suggested in the Amish, but could not be verified by haplotype analyses performed after the assignment of the CHH gene. Here we have carried out segregation analysis of 101 Finnish CHH families, but again, evidence of a significant deficiency of affected members was not found. Nevertheless, among 54 uniplex families, 2 patients with CHH and uniparental disomy (UPD) for chromosome 9 were discovered. UPD might contribute to low segregation ratios by increasing the number of families with only 1 affected individual. These observations show that UPD may occur in an unexpectedly high number of the patients and should be taken into account in the genetic counselling and prenatal diagnostics of CHH families.

Defective in-vitro colony formation of haematopoietic progenitors in patients with cartilage-hair hypoplasia and history of anaemia

Cartilage-hair hypoplasia (CHH) is a metaphyseal chondrodysplasia with short-limbed short stature. The CHH gene has been recently mapped to chromosome 9, and a generalized defect in cellular proliferation has been suggested. Immunological and haematological abnormalities are common findings in CHH. In the present study erythroid, megakaryocyte, and granulocyte-macrophage colony formation in vitro by progenitors from bone marrow and blood was investigated in eight patients with CHH. All patients showed decreased erythroid and megakaryocyte colony formation. Only one patient had a normal granulocyte-macrophage growth, while the others showed decreased numbers of colonies. The defect in colony formation did not correlate with the haemoglobin concentration, platelet count or neutrophil count. The impaired growth was not caused by a decreased number of progenitors as shown by erythroid cultures. The erythroid progenitors were incapable of colony formation in culture conditions sufficient for colony formation by normal progenitors. In a more effectively stimulated culture assay the number of erythroid progenitors was normal or increased.

CONCLUSION

The present study shows defective in vitro colony formation in all myeloid lineages in patients with CHH, which is in accordance with the suggestion of a common cell proliferation defect in CHH.

Cartilage-hair hypoplasia

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High-resolution linkage-disequilibrium mapping of the cartilage-hair hypoplasia gene

We recently assigned the gene for an autosomal recessive skeletal dysplasia, cartilage-hair hypoplasia (CHH), to 9p21-p13 in Finnish and Amish families. An association was observed between CHH and alleles at D9S163 in both family series, suggesting that these loci are in linkage disequilibrium and close to each other. Here we extended these studies by exploiting the linkage-disequilibrium information that can be obtained from families with a single affected child, and we studied 66 Finnish CHH families with seven microsatellite markers. The analysis based on the Luria and Delbrück (1943) method and adapted to the study of human founder populations suggests that the distance between CHH and D9S163 is approximately 0.3 cM. An eight-point linkage analysis modified to take advantage of all possible information in 15 Finnish and 17 Amish families was capable of narrowing the likely location of CHH to within an interval of 1.7 cM on a male map. The peak lod score of 54.92 was attained 0.03 and 0.1 cM proximal to D9S163 on the male and female maps, respectively. These results confirm the power of genetic resolution, that lies in the study of linkage disequilibrium in well-defined founder populations with one major ancestral disease mutation.

Cartilage-hair hypoplasia gene assigned to chromosome 9 by linkage analysis

Cartilage-hair hypoplasia (CHH) is an autosomal recessive skeletal dysplasia of unknown pathogenesis leading to short-limbed stature. Associated features include hypoplasia of hair, abnormal cellular immunity, deficient erythrogenesis, increased risk of malignancies, Hirschsprung disease, and Diamond-Blackfan type hypoplastic anaemia. We mapped the CHH gene by linkage analysis with 5 markers to chromosome 9. Multipoint linkage analysis gives a lod score of 9.94 for a location between D9S43 and D9S50. Based on strong linkage disequilibrium the closest marker, D9S50, is likely to be less than 1 cM from the gene. No heterogeneity was observed in 14 Finnish families, nor was there evidence of reduced penetrance. These results provide a starting point for the eventual cloning and characterization of the CHH gene.

Cartilage-hair hypoplasia--clinical manifestations in 108 Finnish patients

Cartilage-hair hypoplasia is an autosomal recessive metaphyseal chondrodysplasia with short-limbed short stature, hypoplastic hair, and defective immunity and erythrogenesis. We have analysed the clinical outcome of 108 Finnish patients. Birth length was below -2.0 SD in 70% of the patients; the adult heights ranged from -11.4 SD to -5.2 SD. The sitting height percentage was increased in all but 4 patients. Six patients had normal hair. Increased ligamentous laxity was present in 95%, limited extension of the elbows in 92%, increased lumbar lordosis in 85%, thoracal deformity in 68%, genu varum in 63% and scoliosis in 21% of the patients. Defective cellular immunity had been observed in 88% and increased susceptibility to infections in 56% of the patients. Six patients had died of primary infections. The incidence of malignancies was 6%. Childhood anaemia had occurred in 79% of the patients. It was usually mild, but severe in 14 patients. Hirschsprung disease had been observed in 8, anal stenosis in 1 and oesophageal atresia in 1 patient. The intrafamilial variation of the syndrome was considerable as studied in 16 sibships.

Anaemia and macrocytosis--unrecognized features in cartilage-hair hypoplasia

Cartilage-hair hypoplasia is an autosomal recessive osteo-chondrodysplasia which results in short stature, sparse hair and impaired cell-mediated immunity. In a study of 88 Finnish patients we found episodes of anaemia and/or macrocytosis during childhood in 86% of the patients. The reticulocyte index was always low in relation to anaemia. Bone marrow examination revealed decreased erythropoiesis in six of eight anaemic patients studied. Anaemia was most prevalent and severe during infancy. Spontaneous recovery occurred before adulthood in all patients except in three infants with fatal hypoplastic anaemia. Sixty-two percent of the patients had had lymphopenia and 24% neutropenia. Presence of anaemia significantly correlated to severity of immunodeficiency and growth failure and to presence of neutropenia. Disordered erythrogenesis is an integral feature of cartilage-hair hypoplasia and may, together with growth failure and immunodeficiency, reflect a generalized defect in cellular proliferation.

Cartilage-hair hypoplasia in Finland: epidemiological and genetic aspects of 107 patients

Cartilage-hair hypoplasia (CHH) is an autosomal recessive form of metaphyseal chondrodysplasia characterised by short limbed short stature, hypoplastic hair growth, and impaired cell mediated immunity and erythrocyte production. The syndrome is exceptionally prevalent among the Finns and among the Old Order Amish in the United States; sporadic cases have been reported from other countries. An epidemiological and genetic study of CHH in Finland showed 107 patients, 46 males and 61 females, in 85 families. Eighteen of them had died, seven before the age of 1 year. The living patients ranged in age from 1 to 51 years, median 21 years. The incidence was estimated to be 1:23,000 live births. Consanguinity was found in two families and interfamilial relationships in 20 families. Geographical distribution of the birth places of the patients and their great grandparents showed accumulation in a small area in western Finland and regional clusters were seen in other parts of the country as well. The result of the segregation analysis was in accordance with recessive inheritance with reduced penetrance.

Growth in cartilage-hair hypoplasia

Cartilage-hair hypoplasia is an osteochondrodysplasia with short-limbed short stature. The cartilage-hair hypoplasia gene is exceptionally prevalent in Finland; more than 100 patients have been identified. We have analyzed the growth of 100 Finnish patients and present cartilage-hair hypoplasia-specific growth charts of height and weight for height. The disproportions were analyzed by sitting height, subischial leg height, sitting height:height ratio, and span-height difference. The stature was short at birth with a mean relative length of -3.0 SD. The median adult height was 131.1 cm (-7.9 SD, range 110.7 to 149.0 cm) for 15 males and 122.5 cm (-7.9 SD, range 103.7 to 137.4 cm) for 20 females. The progression of the growth failure was partly explained by weakness or absence of pubertal growth spurt. Weight for height was above normal median in childhood and increased further at puberty. Most of the adults were overweight. The adults' mean relative head circumference was -0.9 SD. Growth was disturbed both in the limbs and in the spine, more severely in the limbs. Adult height showed no correlation with the midparent height. The charts are useful for assessment of growth, prediction of adult height, detection of superimposed disorders, and evaluation of growth-accelerating therapy.