LRP6 High Bone Mass Characterized in Two Generations Harboring a Unique Mutation of Low-Density Lipoprotein Receptor-Related Protein 6.

Osteoblast Wnt/ß-catenin signaling conditions skeletal development and health. Bone formation is stimulated when on the osteoblast surface a Wnt binds to low-density lipoprotein receptor-related protein 5 (LRP5) or 6 (LRP6), in turn coupled to a frizzled receptor. Sclerostin and dickkopf1 inhibit osteogenesis if either links selectively to the first ß-propeller of LRP5 or LRP6, thereby disassociating these cognate co-receptors from the frizzled receptor. Sixteen heterozygous mutations identified since 2002 within LRP5 and three heterozygous mutations identified since 2019 within LRP6 prevent this binding of sclerostin or dickkopf1 and account for the exceptionally rare, but highly instructive, autosomal dominant disorders called LRP5 and LRP6 high bone mass (HBM). Herein, we characterize LRP6 HBM in the first large affected family. Their novel heterozygous LRP6 missense mutation (c.719C>T, p.Thr240Ile) was present in two middle-aged sisters and three of their sons. They considered themselves healthy. Their broad jaw and torus palatinus developed during childhood and, contrary to the two previous reports of LRP6 HBM, the appearance of their adult dentition was unremarkable. Skeletal modeling, defined radiographically, supported classification as an endosteal hyperostosis. Areal bone mineral density (g/cm2) of the lumbar spine and total hip featured accelerated increases reaching Z-scores of ~ +8 and +6, respectively, although biochemical markers of bone formation were normal. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Socio-economic deprivation and healthcare service use of young people with type 1 and type 2 diabetes.

AIM: Lower socio-economic status (SES) is linked to greater morbidity in people with young-onset type 2 (T2D) and type 1 diabetes (T1D). We assessed healthcare utilisation from this population and the impact of SES. METHODS: Retrospective analysis of 1,350 people with T2D and 731 with T1D diagnosed between 15-30 years of age referred to secondary diabetes services in Auckland, New Zealand. Primary care visits, referral to/attendance at diabetes clinics, and hospital admissions were recorded; their relationship to a validated national index of deprivation (NZDep) was assessed. RESULTS: The proportion with primary care attendance was similar in both groups with no significant variation with NZDep. For T2D, NZDep was a predictor of delayed referral (≧1-year post-diagnosis) to diabetes services, following adjustment for age and HbA1c in the year of diagnosis (OR 1.15 for every decile increase in NZDep, 95% CI 1.07-1.24, p=0.0003). The median number of appointments offered over a 2-year period was greater for T1D (2.0 (IQR 0, 7) vs (0 (IQR 0, 2), p<0.001); non-attendance increased with NZDep for T2D (p=0.016). The proportion with hospital admissions was similar in both groups and increased with NZDep (T1D p<0.001, T2D p=0.015). CONCLUSION: SES impacts several measures of healthcare utilisation. Current healthcare models are inadequately servicing people with young-onset T2D.

Impact of Bariatric Surgery on Unplanned Hospital Admissions for Infection.

PURPOSE: Both obesity and type 2 diabetes are associated with an increased risk of skin and soft tissue (SSTI), urinary tract, and lower respiratory tract infections but it is not clear whether the incidence of such infections is reduced after bariatric surgery. MATERIALS AND METHODS: In people accepted onto our publicly funded bariatric program, we recorded unplanned admissions to public hospitals over a median follow-up of 4.5 years in those successfully undergoing surgery and in those who withdrew from the program. Rates of admission for the composite outcome (SSTI, urinary tract, or lower respiratory infection) were compared. RESULTS: Of 774 people accepted onto the program, 49% underwent surgery. Infections accounted for 27% of unplanned admissions in those not completing surgery and 13% of those who underwent surgery (p < 0.001). The rate of admission was 60% lower in people who underwent surgery than those who did not: 4.3 vs 12.2 per 100 patient-years (P < 0.002), a difference maintained across 8 years' follow-up. The impact of surgery was independent of enrolment age, BMI, or diabetes and smoking status. Of the three types of infection in the composite outcome, SSTI were the most prevalent and showed the greatest reduction (p < 0.0001). The median day stay for infection was 0.5 day less in those who underwent surgery (p < 0.01). CONCLUSIONS: Hospitalization for these three infectious diseases in people undergoing bariatric surgery was lower than that in people enrolled in the bariatric program but not completing surgery. The effect was greatest for SSTI, and sustained to at least 8 years.

Deletion of the last two exons of FGF10 in a family with LADD syndrome and pulmonary acinar hypoplasia.

Pulmonary acinar hypoplasia (PAH) and lacrimo-auriculo-dento-digital (LADD) syndrome have both been associated with loss-of-function variants in, or deletions of FGF10. Here we report a multi-generational family with seven members manifesting varying features of LADD syndrome, with one individual dying in early infancy of PAH. Whole genome sequencing in one family member identified a 12,158 bp deletion on chromosome 5p12 that removes two of the three exons of FGF10. Allele-specific PCR demonstrated that all affected family members, including the individual with PAH, carried the 12 kb deletion. We conclude the deletion is pathogenic and expands the mutational spectrum of FGF10 variants in LADD syndrome. The common mechanism underlying the variable clinical features of LADD syndrome is defective terminal branching of salivary and lacrimal glands and pulmonary acini, regulated by the TBX4-FGF10-FGFR2 pathway. The variable phenotypic expressivity of FGF10 haploinsufficiency from relatively benign to lethal is likely due to variation at other genetic loci.

Socioeconomic status and risk factors for complications in young people with type 1 or type 2 diabetes: a cross-sectional study.

INTRODUCTION: Young people with type 2 diabetes (T2D) develop complications earlier than those with type 1 diabetes (T1D) of comparable duration, but it is unclear why. This apparent difference in phenotype could relate to relative inequality. RESEARCH DESIGN AND METHODS: Cross-sectional study of young people referred to secondary diabetes services in Auckland, Aotearoa-New Zealand (NZ): 731 with T1D and 1350 with T2D currently aged <40 years, and diagnosed between 15 and 30 years. Outcome measures were risk factors for complications (glycemic control, urine albumin/creatinine ratio (ACR), cardiovascular disease (CVD) risk) in relation to a validated national index of deprivation (New Zealand Deprivation Index (NZDep)). RESULTS: Young people with T2D were an average 3 years older than those with T1D but had a similar duration of diabetes. 71% of those with T2D were of Maori or Pasifika descent, compared with 24% with T1D (p<0.001). T1D cases were distributed evenly across NZDep categories. 78% of T2D cases were living in the lowest four NZDep categories (p<0.001). In both diabetes types, body mass index (BMI) increased progressively across the NZDep spectrum (p<0.002), as did mean glycated hemoglobin (HbA1c) (p<0.001), the prevalence of macroalbuminuria (p≤0.01), and CVD risk (p<0.001). Adjusting for BMI, diabetes type, and duration and age, multiple logistic regression revealed deprivation was the strongest risk factor for poorly controlled diabetes (defined as HbA1c >64 mmol/mol, >8%); OR 1.17, 95% CI 1.13 to 1.22, p<0.0001. Ordinal logistic regression showed each decile increase in NZDep increased the odds of a higher ACR by 11% (OR 1.11, 95% CI 1.06 to 1.16, p<0.001) following adjustment for BMI, blood pressure, diabetes type and duration, HbA1c, and smoking status. Multiple linear regression indicated a 4% increase in CVD risk for every decile increase in NZDep, regardless of diabetes type. CONCLUSIONS: The apparent more aggressive phenotype of young-onset T2D is at least in part explicable by relative deprivation.

Morbidity and mortality after recognition of macroalbuminuria in Pasifika people with type 2 diabetes in a primary health-care practice.

INTRODUCTION Macroalbuminuria in people with type 2 diabetes is common among Pasifika peoples and is associated with end-stage kidney disease and major cardiovascular disease. AIM In a primary care practice catering for Pasifika people, to determine the time after first recognition of macroalbuminuria to the occurrence of major cardiovascular and renal events, and to examine the relationship with retinopathy status. METHODS In a retrospective observational cohort study, we documented the occurrence of major cardiovascular events and amputations, end-stage kidney disease and death in 115 people with type 2 diabetes reviewed by a specialist diabetes physician at the Langimalie Tongan Health practice between 2005 and 2018. The follow up was 1-19 (median 9.5) years from the first recognition of macroalbuminuria (albumin:creatinine ratio of >30 g/mol). Survival was described by using Kaplan-Meier analysis. RESULTS Macroalbuminuria was detected a mean of 9 years after the diagnosis of diabetes, at a mean age of 52 (standard deviation 12) years. Within 6 years of macroalbuminuria detection, 4% of people had died, 15% had reached end-stage kidney disease, 15% had cardiovascular events or amputations and 30% had the composite outcome of any of these. Within 12 years, the respective proportions were: 24%, 29%, 20% and 48%. The composite outcome was less frequent (P < 0.002) in patients without retinopathy at the time macroalbuminuria was recognised. Compared to patients with retinopathy, this group were younger (P = 0.025), more obese (P < 0.0001), had better baseline renal function (P = 0.018) and a shorter interval between the diagnosis of diabetes and recognition of macroalbuminuria (P < 0.0001). DISCUSSION In this Pasifika population, macroalbuminuria was a marker for serious adverse cardiovascular and renal disease, and mortality, but in the 29% of patients without retinopathy at the time of recognition of macroalbuminuria, the natural history was more benign. The management of such comorbid patients is a substantial challenge for primary health-care services.

Does brittle cornea syndrome have a bone fragility phenotype?

Brittle cornea syndrome is a rare recessively inherited disorder (a sub-type of Ehlers-Danlos syndrome) with a clinical presentation dominated by corneal fragility and deafness. There have been suggestions that it may also have a bone fragility phenotype, but there has been little detailed description. We describe two siblings with brittle cornea syndrome due to compound heterozygous mutations in ZNF469 who had sustained ten or more fractures, the majority before the age of 15. When investigated as adults they had osteopenia, with lower z-scores than their parents who each carried one mutation. A bone biopsy from one sibling showed reduced cortical porosity. Both parents, who were heterozygous mutation carriers, had also suffered fractures but had normal bone density. This data supports the view that brittle cornea syndrome may have a bone fragility phenotype.

Insulin use and new diabetes after acceptance for bariatric surgery: comparison of outcomes after completion of surgery or withdrawal from the program.

INTRODUCTION: In people accepted onto a bariatric surgery program we compared diabetes-related outcomes in those who completed surgery with those who withdrew before having surgery-examining rates of insulin use in people with type 2 diabetes (T2D), and rates of incident diabetes in people without pre-existing T2D. RESEARCH DESIGN AND METHODS: 771 people were accepted onto the program. 463 people (60%) had T2D at referral, of which 48% completed surgery and 52% withdrew. Of 308 people without T2D at referral, 49% completed surgery, and 51% withdrew. Rates of insulin use and incident diabetes were compared by Kaplan-Meier analyses. Among those with pre-existing T2D, we examined rates of remission and relapse after surgery. RESULTS: People without T2D who withdrew from the program had higher mean body mass index and glycated hemoglobin levels than those completing surgery (p<0.005). The rate of incident diabetes at 5 years was 19% in those who withdrew versus 0% in those completing surgery (p<0.001). 30% of people with T2D were taking insulin at referral and all stopped insulin after surgery. During follow-up, the rate of insulin (re)introduction was lower in those who completed surgery (8% vs 26% at 5 years, p<0.001). Of those with T2D who completed surgery, 80% had remission, but 34% had relapsed by 5 years. Diabetes relapse was associated with less weight loss after surgery, a longer duration of T2D and previous insulin use. CONCLUSIONS: Despite a high relapse rate, people with T2D who completed surgery had lower insulin use at 5 years than those withdrawing from the program. In people without T2D, bariatric surgery prevented incident diabetes. People without T2D who withdrew from the program were at greater risk of diabetes, suggesting those who could benefit the most in terms of T2D prevention are not completing bariatric surgery.

Bisphosphonate-Induced Deterioration of Osteomalacia in Undiagnosed Adult Fanconi Syndrome.

We describe two women with a misdiagnosed fracturing bone disease who were treated erroneously with i.v. zoledronate. Over the next year, they suffered marked clinical and radiographic deterioration in skeletal disease. Both were eventually diagnosed with hypophosphatemic osteomalacia secondary to acquired Fanconi syndrome (caused by light-chain myeloma in one case and tenofovir treatment in the other). Appropriate treatment with phosphate supplementation was instituted with clinical improvement. These cases illustrate the importance of not missing osteomalacia in adults presenting with fractures, and the potentially damaging effects of treatment with long-acting inhibitors of bone resorption in these circumstances. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

A Novel Disorder of Osteoporosis, Osteonecrosis, and Metaphyseal Fracture.

We describe two unrelated women who in their fifth decade developed a severe disorder characterized by large joint osteonecrosis and multiple minimal trauma fractures in both the axial and appendicular skeleton, including unusual metaphyseal fractures of the proximal tibia. Bone density testing showed borderline osteoporosis of the spine and osteopenia of the femur. Therapy with bisphosphonates and teriparatide failed to prevent further fractures. To our knowledge, this disorder has not been described previously. Investigations to date, including a genetic screen, have not revealed its cause. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

HYPOPHOSPHATEMIC RICKETS WITH HYPERCALCIURIA: A NOVEL HOMOZYGOUS MUTATION IN SLC34A3 AND LITERATURE REVIEW.

OBJECTIVE: Hypophosphatemic rickets with hypercalciuria (HHRH) is a rare, recessively-inherited form of rickets caused by homozygous or compound heterozygous mutations in the SLC34A3 gene that encodes the renal tubular phosphate transporter protein NaPi2c. The bone phenotype varies from severe rickets to no disease. Accurate diagnosis is important as the treatment differs from other forms of rickets. METHODS: The patient was a 12-year-old boy from the Indian subcontinent with florid hypophosphatemic rickets. A targeted gene panel to search for mutations in genes associated with inherited forms of rickets was performed. We also completed a literature search of published cases of HHRH. RESULTS: The targeted gene panel demonstrated a novel homozygous SLC34A3 mutation: c.1339 G>A (p.Ala447Thr). His parents were heterozygous for the mutation. In our literature review we found that people with homozygous SLC34A3 mutations were more likely to have rickets than those with compound heterozygous mutations (85% versus 45%, p<0.002) and that serum phosphate z scores were lower in those with rickets than those without (-3.3 with a standard deviation of 1.5 versus -2.1 with a standard deviation of 1.5, p<0.005). CONCLUSION: The bone phenotype of HHRH is related to the nature of the mutation and serum phosphate levels. Targeted gene panels can aid in the accurate diagnosis of inherited forms of rickets, and facilitate correct treatment.

Increased Peripheral Blood Heteroplasmy of the mt.3243A>G Mutation Is Associated with Earlier End-Stage Kidney Disease: A Case Report and Review of the Literature.

The mitochondrial DNA mutation mt.3243A>G is most commonly associated with maternally inherited diabetes and deafness (MIM 52,000), but it has protean phenotypes including renal disease due to focal segmental glomerulosclerosis. We describe monozygotic twins who both harboured this mutation and developed ESRD. Although otherwise genetically identical, the twins differed in their peripheral blood leucocyte levels of circulating mt.3243A>G heteroplasmy: 20 versus 10%, when assessed at 42 years of age. The twin with the higher heteroplasmy load developed end-stage kidney disease 15 years earlier than her sister. A review of the published literature supports a relationship between heteroplasmy level and the age at the development of the end stage of renal failure in patients with mt.3243A>G-related kidney disease.

Juvenile Paget's disease with compound heterozygous mutations in TNFRSF11B presenting with recurrent clavicular fractures and a mild skeletal phenotype.

Juvenile Paget's disease (JPD) is a rare recessively-inherited bone dysplasia. The great majority of cases described to date have had homozygous mutations in TNFRSF11B, the gene encoding osteoprotegerin. We describe a boy who presented with recurrent clavicular fractures following minor trauma (8 fractures from age 2 to 11). He was of normal height and despite mild lateral bowing of the thighs and anterior bowing of the shins he remained physically active. Abnormal modelling was noted in ribs and humeri on clavicular radiographs, and a skeletal survey at the age of 7 showed generalised diaphyseal expansion of the long bones with thickening of the periosteal and endosteal surfaces of the cortices. On biochemical evaluation, serum alkaline phosphatase was noted to be persistently elevated. The diagnosis of JPD was confirmed by the finding of compound heterozygous mutations in TNFRSF11B: a maternally-inherited A>G missense mutation at position 1 of the first amino acid codon (previously reported) and a paternally-inherited splice acceptor site mutation in intron 3 at a highly conserved position (not previously reported). Bioinformatics analysis suggested both mutations were disease-causing. Compound heterozygote mutations in TNFRSF11B causing JPD have been previously reported only once - in a boy who also had a relatively mild skeletal phenotype. The milder features may lead to delay in diagnosis and diagnostic confusion with other entities, but the extraskeletal features of JPD may nonetheless develop.

Bisphosphonate Use and Fractures in Adults with Hypophosphatasia.

Adults with hypophosphatasia (HPP) may suffer femoral fractures resembling the atypical femoral fractures that can occur with long-term bisphosphonate treatment, and there is an emerging consensus that bisphosphonates should not be used in adults with HPP and low bone mass. However, the spectrum of HPP in adults is wide: ranging from the severely affected-who commonly have osteomalacia-through to the minimally affected. The former typically have biallelic and the latter, heterozygous ALPL mutations. We have reviewed reports of fractures in adults with genetically proven HPP which suggest that the risk of fracture is at least 200-fold greater in those with biallelic mutations. We also discuss two cases of postmenopausal women with heterozygous ALPL mutations. One had fractures and severe osteoporosis, but histology revealed no evidence of osteomalacia. The second had taken alendronate for 8 years, but despite profound suppression of bone turnover, histology again revealed no evidence of osteomalacia. The management of adults with HPP who have coexisting osteoporosis is challenging. More data are clearly needed, but we suggest that the risks of bisphosphonate therapy may be relatively low in patients who have heterozygous mutations and no histological evidence of osteomalacia. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Compound heterozygosity for a frameshift mutation and an upstream deletion that reduces expression of SERPINH1 in siblings with a moderate form of osteogenesis imperfecta.

SERPINH1 encodes the collagen chaperone HSP47 that binds to arginine-rich sequences in the type I procollagen trimers and provides the final steps in the folding and stabilization of the triple helical domain. Loss of both alleles in mice results in very early embryonic lethality. SERPINH1 mutations have been associated with one of the rarest forms of recessively inherited osteogenesis imperfecta (OI) with a moderate to severe phenotype. We identified a family with non-consanguineous unaffected parents who had two children with moderate short stature, low bone density, and fractures. Both children were compound heterozygotes for two mutations: a frameshift in the last exon that deleted the RER retention signal, and a 5,274 bp deletion 2.37 kb upstream from the transcription start site. The maternally-inherited frameshift allele was expressed at normal levels, but the protein was unstable. The mRNA encoded by the second allele represented about 50% of that from the frameshift-containing allele. The upstream deletion was inherited from the father, and the mRNA encoded by that allele in his cultured dermal fibroblasts was also expressed at a low level, which confirmed that this domain had a regulatory function for SERPINH1. Regulatory mutations are uncommon causes of human genetic disorders, and the ability to measure expression levels in appropriate cells is key to their identification.