Monica Grover

WNT1 Mutations in Early-Onset Osteoporosis and Osteogenesis Imperfecta

This report identifies human skeletal diseases associated with mutations in WNT1. In 10 family members with dominantly inherited, early-onset osteoporosis, we identified a heterozygous missense mutation in WNT1, c.652T→G (p.Cys218Gly). In a separate family with 2 siblings affected by recessive osteogenesis imperfecta, we identified a homozygous nonsense mutation, c.884C→A, p.Ser295*. In vitro, aberrant forms of the WNT1 protein showed impaired capacity to induce canonical WNT signaling, their target genes, and mineralization. In mice, Wnt1 was clearly expressed in bone marrow, especially in B-cell lineage and hematopoietic progenitors; lineage tracing identified the expression of the gene in a subset of osteocytes, suggesting the presence of altered cross-talk in WNT signaling between the hematopoietic and osteoblastic lineage cells in these diseases.

Phenotypic Variability of Osteogenesis Imperfecta Type V Caused by an IFITM5 Mutation

In a large cohort of osteogenesis imperfecta type V (OI type V) patients (17 individuals from 12 families), we identified the same mutation in the 5′ untranslated region (5′UTR) of the interferon‐induced transmembrane protein 5 (IFITM5) gene by whole exome and Sanger sequencing (IFITM5 c.–14C > T) and provide a detailed description of their phenotype. This mutation leads to the creation of a novel start codon adding five residues to IFITM5 and was recently reported in several other OI type V families. The variability of the phenotype was quite large even within families. Whereas some patients presented with the typical calcification of the forearm interosseous membrane, radial head dislocation and hyperplastic callus (HPC) formation following fractures, others had only some of the typical OI type V findings. Thirteen had calcification of interosseous membranes, 14 had radial head dislocations, 10 had HPC, 9 had long bone bowing, 11 could ambulate without assistance, and 1 had mild unilateral mixed hearing loss. The bone mineral density varied greatly, even within families. Our study thus highlights the phenotypic variability of OI type V caused by the IFITM5 mutation.

Assessment of bone mineral status in children with Marfan syndrome.

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder with skeletal involvement. It is caused by mutations in fibrillin1 (FBN1) gene resulting in activation of TGF‐β, which developmentally regulates bone mass and matrix properties. There is no consensus regarding bone mineralization in children with MFS. Using dual‐energy X‐ray absorptiometry (DXA), we evaluated bone mineralization in 20 children with MFS unselected for bone problems. z‐Scores were calculated based on age, gender, height, and ethnicity matched controls. Mean whole body bone mineral content (BMC) z‐score was 0.26 ± 1.42 (P = 0.41). Mean bone mineral density (BMD) z‐score for whole body was −0.34 ± 1.4 (P = 0.29) and lumbar spine was reduced at −0.55 ± 1.34 (P = 0.017). On further adjusting for stature, which is usually higher in MFS, mean BMC z‐score was reduced at −0.677 ± 1.37 (P = 0.04), mean BMD z‐score for whole body was −0.82 ± 1.55 (P = 0.002) and for lumbar spine was −0.83 ± 1.32 (P = 0.001). An increased risk of osteoporosis in MFS is controversial. DXA has limitations in large skeletons because it tends to overestimate BMD and BMC. By adjusting results for height, age, gender, and ethnicity, we found that MFS patients have significantly lower BMC and BMD in whole body and lumbar spine. Evaluation of diet, exercise, vitamin D status, and bone turnover markers will help gain insight into pathogenesis of the reduced bone mass. Further, larger longitudinal studies are required to evaluate the natural history, incidence of fractures, and effects of pharmacological therapy.

Decreased bone mineralization in children with Noonan syndrome: another consequence of dysregulated RAS MAPKinase pathway?

INTRODUCTION Noonan syndrome (NS) is a disorder of RAS- mitogen activated protein kinase (MAPK) pathway with clinical features of skeletal dysplasia. This pathway is essential for regulation of cell differentiation and growth including bone homeostasis. Currently, limited information exists regarding bone mineralization in NS. MATERIALS AND METHODS Using dual-energy X-ray absorptiometry (DXA), bone mineralization was evaluated in 12 subjects (mean age 8.7 years) with clinical features of NS. All subjects underwent genetic testing which showed mutations in PTPN11 gene (N=8) and SOS1 gene (N=1). In a subgroup of subjects with low bone mass, indices of calcium-phosphate metabolism and bone turnover were obtained. RESULTS 50% of subjects had low bone mass as measured by DXA. Z-scores for bone mineral content (BMC) were calculated based on age, gender, height, and ethnicity. Mean BMC z-score was marginally decreased at -0.89 {95% CI -2.01 to 0.23; p=0.1}. Mean total body bone mineral density (BMD) z-score was significantly reduced at -1.87 {95% CI -2.73 to -1.0; p=0.001}. Mean height percentile was close to - 2 SD for this cohort, thus total body BMD z-scores were recalculated, adjusting for height age. Adjusted mean total body BMD z-score was less reduced but still significant at -0.82 {95% CI -1.39 to -0.25; p=0.009}. Biochemical evaluation for bone turnover was unremarkable except serum IGF-I and IGF-BP3 levels which were low-normal for age. DISCUSSION Children with NS have a significantly lower total body BMD compared to age, gender, ethnicity and height matched controls. In addition, total BMC appears to trend lower in children with NS compared to controls. We conclude that the metabolic bone disease present resulted from a subtle variation in the interplay of osteoclast and osteoblast activity, without clear abnormalities being defined in the metabolism of either. Clinical significance of this finding needs to be validated by larger longitudinal studies. Also, histomorphometric analysis of bone tissue from NS patients and mouse model of NS may further elucidate the relationship between the RAS-MAPK pathway and skeletal homeostasis.

Autoimmune polyglandular syndrome Type 3 and growth hormone deficiency.

Quintos JB, Grover M, Boney CM, Salas M. Autoimmune polyglandular syndrome type 3 and growth hormone deficiency.

Losartan increases bone mass and accelerates chondrocyte hypertrophy in developing skeleton

Angiotensin receptor blockers (ARBs) are a group of anti-hypertensive drugs that are widely used to treat pediatric hypertension. Recent application of ARBs to treat diseases such as Marfan syndrome or Alport syndrome has shown positive outcomes in animal and human studies, suggesting a broader therapeutic potential for this class of drugs. Multiple studies have reported a benefit of ARBs on adult bone homeostasis; however, its effect on the growing skeleton in children is unknown. We investigated the effect of Losartan, an ARB, in regulating bone mass and cartilage during development in mice. Wild type mice were treated with Losartan from birth until 6 weeks of age, after which bones were collected for microCT and histomorphometric analyses. Losartan increased trabecular bone volume vs. tissue volume (a 98% increase) and cortical thickness (a 9% increase) in 6-weeks old wild type mice. The bone changes were attributed to decreased osteoclastogenesis as demonstrated by reduced osteoclast number per bone surface in vivo and suppressed osteoclast differentiation in vitro. At the molecular level, Angiotensin II-induced ERK1/2 phosphorylation in RAW cells was attenuated by Losartan. Similarly, RANKL-induced ERK1/2 phosphorylation was suppressed by Losartan, suggesting a convergence of RANKL and angiotensin signaling at the level of ERK1/2 regulation. To assess the effect of Losartan on cartilage development, we examined the cartilage phenotype of wild type mice treated with Losartan in utero from conception to 1 day of age. Growth plates of these mice showed an elongated hypertrophic chondrocyte zone and increased Col10a1 expression level, with minimal changes in chondrocyte proliferation. Altogether, inhibition of the angiotensin pathway by Losartan increases bone mass and accelerates chondrocyte hypertrophy in growth plate during skeletal development.

Case report: long-term follow-up of a 45,X male with SHOX haploinsufficiency.

Abstract The 45,X disorder of sexual differentiation (DSD) is a rare disorder. We report long-term follow-up of a 5-year-old African-American male whose evaluation for short stature revealed a karyotype of 45,X der(X)t(X;Y)(p22.3;p11.2)(SRY+). Presence of the SRY (sex-determining region Y) gene resulted in his male development. His chromosome abnormality also resulted in a deletion of the SHOX (short stature homeobox-containing) gene, which partly contributed to his short stature and skeletal features. He underwent normal spontaneous pubertal development, but his final height remained compromised due to advanced bone age, non-optimal response to recombinant human growth hormone (rhGH) treatment during the period of compliance and ultimately non-compliance with rhGH therapy. To our knowledge, this is the first case report describing long-term follow-up of a 45,X male DSD which highlights the similarities and differences from Turner syndrome females.

The Impact of Frequency and Tone of Parent–Youth Communication on Type 1 Diabetes Management

BackgroundThe purpose of this study is to assess the impact of frequency and tone of parent–youth communication on glycemic control as measured by the Family Communication Inventory (FCI). Adolescence provides a unique set of diabetes management challenges, including suboptimal glycemic control. Continued parental involvement in diabetes management is associated with improved HbA1c outcomes; however, diabetes-related conflict within the family can have adverse effects. Although it is clear that communication plays an important role in diabetes outcomes, the specific impact of frequency and tone of such communication is largely understudied.MethodsA total of 110 youths with type 1 diabetes and their parents completed questionnaires assessing diabetes-related adherence, family conflict, and family communication (i.e., frequency and tone) during a routine clinic visit. Routine testing of HbA1c was performed.ResultsYouth- and parent-reported frequency of communication were unrelated to HbA1c. Instead, greater discrepancies between parents and children on reported frequency of communication (most commonly parents reporting frequent and youth reporting less frequent communication) corresponded with poorer glycemic control and increased family conflict. More positive tone of communication as rated by youth was associated with lower HbA1c.ConclusionsDiabetes-related communication is more complex than conveyed simply by how often children and their parents communicate. Tone of communication and discrepancies in a family’s perception of the frequency of communication were better than frequency as predictors of glycemic control. The FCI appears to capture the frequency and tone of diabetes-related communication, though larger-scale studies are warranted to inform future use of this scale.

Osteoporosis in Children with Chronic Illnesses: Diagnosis, Monitoring, and Treatment

Purpose of ReviewOsteoporosis is an under-recognized complication of chronic illness in childhood. This review will summarize recent literature addressing the risk factors, evaluation, and treatment for early bone fragility.Recent FindingsCriteria for the diagnosis of pediatric osteoporosis include the presence of low trauma vertebral fractures alone or the combination of low bone mineral density and several long bone fractures. Monitoring for bone health may include screening for vertebral fractures that are common but often asymptomatic. Pharmacologic agents should be offered to those with fragility fractures especially when spontaneous recovery is unlikely. Controversies persist about the optimal bisphosphonate agent, dose, and duration. Newer osteoporosis drugs have not yet been adequately tested in pediatrics, though clinical trials are underway.SummaryThe prevalence of osteoporosis is increased in children with chronic illness. To reduce the frequency of fragility fractures requires increased attention to risk factors, early intervention, and additional research to optimize therapy and potentially prevent their occurrence.

Treatment of Adolescent Osteoporosis

The diagnosis and management of osteoporosis in adolescents differ in several ways from the care of older adults. The diagnosis cannot be based upon low bone mineral density alone. The criteria for osteoporosis in a pediatric patient include a low trauma vertebral fracture or low bone density for age and a significant fracture history (2 or more long bone fractures before age 10 or 3 or more long bone fractures before age 19). Since many vertebral fractures are asymptomatic, radiographic screening is important for youth at high risk. Primary osteoporosis results from heritable disorders, whereas secondary osteoporosis is acquired as a consequence of chronic disease and the medications used for treatment. The myriad disorders linked to bone fragility share one or more common skeletal risk factors including nutritional deficits, reduced mobility, increased inflammatory cytokines, sex steroid or growth hormone deficiency, and osteotoxic drug therapy. The net result is reduced bone formation, which may be compounded by increased bone resorption. Growing children have the potential to restore bone strength if they recover from illness, whereas pharmacologic therapy may be indicated on a compassionate basis for patients with fragility fractures and limited potential to recover spontaneously. Primary care providers can play a critical role by identifying teens at risk for bone fragility, by encouraging optimal nutrition (including protein, calcium, and vitamin D) and physical activity, and by referring to physicians with expertise in pediatric osteoporosis. The goal of this chapter is to educate providers about current consensus and controversy on the use of osteoporosis drugs in adolescents.