Genetic basis of osteogenesis imperfecta from a single tertiary centre in South Africa.

Osteogenesis imperfecta (OI) is a clinically heterogeneous disorder characterised by skeletal fragility and an increased fracture incidence. It occurs in approximately one in every 15-20,000 births and is known to vary considerably in its severity. This report aimed to use next-generation sequencing (NGS) technology to identify disease genes and causal variants in South African patients with clinical-radiological features of OI. A total of 50 affected individuals were recruited at Tygerberg Hospital's Medical Genetics clinic. Patients were selected for a gene panel test (n = 39), a single variant test (n = 1) or exome sequencing (ES) (n = 12, 7 singletons, 1 affected duo, and 1 trio), depending on funding eligibility. An in-house genomic bioinformatics pipeline was developed for the ES samples using open-source software and tools. This study's 100% diagnostic yield was largely attributable to an accurate clinical diagnosis. A causal variant in COL1A1 or COL1A2 was identified in 94% of this patient cohort, which is in line with previous studies. Interestingly, this study was the first to identify the common South African pathogenic FKBP10 variant in a patient of mixed ancestry, adding to what was previously known about this variant in our population. Additionally, a recurrent variant in COL1A2: c.1892G>T was discovered in 27 individuals (25 from three large unrelated families and two further individuals), facilitating the establishment of local testing for this variant in South African patients.

Performance of glucagon stimulation test in diagnosing central adrenal insufficiency in children when utilising the Roche Elecsys® cortisol II assay: a pilot study.

OBJECTIVES: The glucagon stimulation test (GST) is used for the simultaneous assessment of central adrenal insufficiency (CAI) and growth hormone deficiency. The new Roche cortisol II (C II) assay was recently introduced, confounding interpretation of the GST. The performance of the GST in diagnosing central adrenal insufficiency (CAI), utilising the C II assay, was therefore compared with that of the overnight metyrapone test (ONMTPT). METHODS: A diagnostic accuracy study was performed by retrospectively analysing folders and laboratory records of 25 children and adolescents investigated for hypopituitarism with the GST and the ONMTPT between September 2016 and December 2019. The peak serum cortisol (C) of the GST, the post-metyrapone serum 11-deoxycortisol and adrenocorticotropin levels of the ONMTPT were recorded. Diagnostic performance of the GST at a previously suggested cut-off of 374 nmol/L was evaluated. RESULTS: Seventeen boys and 8 girls, aged 1.7-16.3 years (median 7.3 years) were identified. The sensitivity of the post-GST C-level at 374 nmol/L was 0.40 (95% confidence interval [CI] 0.17-0.69), specificity 0.64 (95% CI 0.39-0.84), positive predictive value 0.44 (95% CI 0.19-0.73), negative predictive value 0.60 (95% CI 0.36-0.80), accuracy 0.54 (95% CI 0.35-0.72), positive likelihood ratio (+LR) 0.93 (95% CI 0.49-1.77) and negative LR 1.12 (95% CI 0.40-3.15). The area under the receiver of operating characteristics (ROC) curve was 0.379 (95% CI 0.142-0.615). CONCLUSIONS: This study suggests that the GST at any C II cut-off cannot replace the ONMTPT as a diagnostic test for CAI in children. Findings should be confirmed in a larger study.

Hypothalamic-pituitary-adrenal axis suppression in asthma: A glucocorticoid receptor polymorphism may protect.

BACKGROUND: Asthmatic children on corticosteroids can develop hypothalamic-pituitary-adrenal axis suppression (HPAS). Single nucleotide polymorphisms (SNPs) rs242941 and rs1876828 of the corticotrophin-releasing hormone receptor 1 (CRHR1) gene were associated with lower stimulated cortisol (F) levels, whereas rs41423247 of the glucocorticoid receptor (NR3C1) gene was associated with higher basal F levels. The objective of the current study was to confirm whether these three SNPs are associated with HPAS in asthmatic children. METHODS: DNA was extracted from saliva obtained from 95 asthmatic children, who had previously undergone basal F and metyrapone testing. Thirty-six children were classified as suppressed. Non-suppressed children were subclassified according to their post-metyrapone adrenocorticotropin (PMTP ACTH) level into a middle (106-319 pg/mL) and a high (>319 pg/mL) ACTH response group. TaqMan® polymerase chain reaction assays were utilized. RESULTS: Only rs41423247 was inversely associated with HPAS (OR = 0.27 [95% CI 0.06-0.90]). Its GC genotype was inversely associated with HPAS (log odds = -1.28, P = .021). √PMTP ACTH was associated with CC (effect size = 10.85, P = .005) and GC genotypes (effect size = 4.06, P = .023). The C allele is inherited as a dominant trait (effect size = -1.31 (95% CI -2.39--0.33; P = .012). In the high ACTH response group, both genotypes affected the PMTP ACTH (effect sizes 1.41 and 15.46; P-values .023 and <2 × 10-26 for GC and CC, respectively). CONCLUSIONS: The C allele of rs41423247 was found to be protective against HPAS. CC genotype is associated with the highest PMTP ACTH response.

Case report: An index of suspicion in hyponatraemia.

Serum indices can give valuable information and should be interpreted as a result. Lipaemia can influence results through different mechanisms, an important one being the electrolyte exclusion effect. A case of pseudohyponatraemia due to this is reported. A 15-year-old female with type 2 diabetes was seen for follow-up. Her biochemistry results revealed severe hyponatraemia of 118 mmol/L. Her capillary glucose concentration was 13.7 mmol/L with a corrected sodium of 122 mmol/L. A lipaemic index of 3+ (absolute value 1320) was noted, which was not flagged by the laboratory information system, as it was below the critical lipaemia limit for sodium determination. Repeated analysis of the same sample using a direct ion selective electrode method, the serum sodium concentration was 134 mmol/L (sodium corrected for glucose = 138 mmol/L). A triglyceride concentration was requested, which was severely raised (100.1 mmol/L). The electrolyte exclusion effect is an analytical phenomenon that causes falsely low electrolyte concentrations in the presence of severe lipaemia or hyperproteinaemia when using indirect analytical methods. These methods are used on many modern-day automated chemistry analysers and should be considered in a patient with asymptomatic hyponatraemia.

Screening for hypothalamic-pituitary-adrenal axis suppression in asthmatic children remains problematic: a cross-sectional study.

OBJECTIVE: To determine which parameter is the most useful screening test for hypothalamic-pituitary-adrenal suppression in asthmatic children. DESIGN: Cross-sectional study. SETTING: Paediatric allergy clinics in Cape Town, South Africa. PARTICIPANTS: 143 asthmatic children of mostly mixed ancestry, aged 5-12 years. OUTCOME MEASURES: Primary outcome measures included Spearman correlation coefficients (r) calculated between the postmetyrapone (PMTP) serum adrenocorticotropic hormone (ACTH), 11-deoxycortisol (11DOC), 11DOC+ cortisol (C) and height, weight, height velocity, weight velocity, change in systolic blood pressure from supine to standing, early morning urinary free cortisol (UFC), morning C, ACTH and dehydroepiandrosterone sulfate (DHEAS). Secondary outcome measures were the receiver operating characteristics (ROC) curve and the diagnostic statistics for the most promising test. RESULTS: All screening variables were weakly correlated with the three PMTP outcomes. Only DHEAS and UFC (nmol/m(2)) were statistically significant-DHEAS for PMTP ACTH and 11DOC (r=0.20, p=0.025 and r=0.21, p=0.017); UFC (nmol/m(2)) for PMTP 11DOC and 11DOC+C (r=0.19, p=0.033 and r=0.20, p=0.022). The area under ROC curve for DHEAS in the 5-year to 9-year age group was 0.69 (95% CI 0.47 to 0.92). At DHEAS cut-off of 0.2 µmol/L: sensitivity=0.88 (CI 0.47 to 1.00), specificity=0.61 (CI 0.42 to 0.78), positive predictive value=0.37 (CI 0.16 to 0.62), negative predictive value=0.95 (CI 0.75 to 1.00), accuracy=0.67 (CI 0.50 to 0.81), positive likelihood ratio=2.26 (CI 1.35 to 3.78), negative likelihood ratio=0.20 (CI 0.03 to 1.30). CONCLUSIONS: No parameter is useful as a universal screening test. DHEAS may be suitable to exclude HPAS before adrenarche. Further research is needed to confirm these findings and identify factors, for example, genetic that may predict or protect against HPAS.

Biceps skin-fold thickness may detect and predict early lipoatrophy in HIV-infected children.

BACKGROUND: The prevalence of potentially stigmatizing lipoatrophy in children receiving antiretroviral therapy in Southern Africa is high, affecting around a third of children. Early diagnosis of lipoatrophy is essential for effective intervention to arrest progression. METHODS: Prepubertal children receiving antiretroviral therapy were recruited from a hospital-based family HIV clinic in Cape Town and followed up prospectively. Lipoatrophy was identified and graded by consensus between 2 HIV pediatricians. A dietician performed anthropometric measurements of trunk and limb fat. Anthropometric measurements in children with and without lipoatrophy were compared using multivariable linear regression adjusting for age and gender. The most discerning anthropometric indicators of lipoatrophy underwent receiver operating characteristic curve analysis. The precision of anthropometric measurements performed by an inexperienced healthcare worker was compared with that of a research dietician. RESULTS: Of 100 recruits, 36 had lipoatrophy at baseline and a further 9 developed lipoatrophy by 15-month follow-up. Annual incidence of lipoatrophy was 12% (confidence interval [CI]: 5-20%) per person-year of follow-up. A biceps skin-fold thickness <5 mm at baseline had a sensitivity of 89% (CI: 67-100%) and a specificity of 60% (CI: 46-75%) for predicting development of lipoatrophy by 15-month follow-up. Negative and positive predictive values were 97% (CI: 91-100%) and 32% (CI: 14-50%). CONCLUSION: Biceps skin-fold thickness <5 mm in prepubertal children exposed to thymidine analogue-based antiretroviral therapy may be a useful screening tool to identify children who are likely to develop lipoatrophy. The variation in precision of measurements performed by an inexperienced healthcare worker only marginally impacted performance.

High prevalence of lipoatrophy in pre-pubertal South African children on antiretroviral therapy: a cross-sectional study.

BACKGROUND: Despite changes in WHO guidelines, stavudine is still used extensively for treatment of pediatric HIV in the developing world. Lipoatrophy in sub-Saharan African children can be stigmatizing and have far-reaching consequences. The severity and extent of lipoatrophy in pre-pubertal children living in sub-Saharan Africa is unknown. METHODS: In this cross-sectional study, children who were 3-12 years old, on antiretroviral therapy and pre-pubertal were recruited from a Family HIV Clinic in South Africa. Lipoatrophy was identified and graded by consensus between two HIV pediatricians using a standardized grading scale. A professional dietician performed formal dietary assessment and anthropometric measurements of trunk and limb fat. Previous antiretroviral exposures were recorded. In a Dual-Energy X-ray Absorbtiometry (DXA) substudy body composition was determined in 42 participants. RESULTS: Among 100 recruits, the prevalence of visually obvious lipoatrophy was 36% (95% CI: 27%-45%). Anthropometry and DXA measurements corroborated the clinical diagnosis of lipoatrophy: Both confirmed significant, substantial extremity fat loss in children with visually obvious lipoatrophy, when adjusted for age and sex. Adjusted odds ratio for developing lipoatrophy was 1.9 (95% CI: 1.3 - 2.9) for each additional year of accumulated exposure to standard dose stavudine. Cumulative time on standard dose stavudine was significantly associated with reductions in biceps and triceps skin-fold thickness (p=0.008). CONCLUSIONS: The prevalence of visually obvious lipoatrophy in pre-pubertal South African children on antiretroviral therapy is high. The amount of stavudine that children are exposed to needs review. Resources are needed to enable low-and-middle-income countries to provide suitable pediatric-formulated alternatives to stavudine-based pediatric regimens. The standard stavudine dose for children may need to be reduced. Diagnosis of lipoatrophy at an early stage is important to allow timeous antiretroviral switching to arrest progression and avoid stigmatization. Diagnosis using visual grading requires training and experience, and DXA and comprehensive anthropometry are not commonly available. A simple objective screening tool is needed to identify early lipoatrophy in resource-limited settings where specialized skills and equipment are not available.

Hypothalamic-pituitary-adrenal axis suppression in asthmatic school children.

BACKGROUND AND OBJECTIVE: Hypothalamic-pituitary-adrenal axis suppression (HPAS) when treating children with corticosteroids is thought to be rare. Our objective was to determine the prevalence of and predictive factors for various degrees of HPAS. METHODS: Clinical features of HPAS, doses, adherence, asthma score, and lung functions were recorded in 143 asthmatic children. The overnight metyrapone test was performed if morning cortisol was >83 nmol/L. Spearman correlations coefficients (r) were calculated between 3 postmetyrapone outcomes and each continuous variable. A multiple linear regression model of √postmetyrapone adrenocorticotropic hormone (ACTH) and a logistic regression model for HPAS were developed. RESULTS: Hypocortisolemia was seen in 6.1% (1.8-10.5), hypothalamic-pituitary suppression (HPS) in 22.2% (14.5-29.9), adrenal suppression in 32.3% (23.7-40.9), HPAS in 16.3% (9.3-23.3), and any hypothalamic-pituitary-adrenal axis dysfunction in 65.1% (56.5-72.9). Log daily nasal steroid (NS) dose/m(2) was associated with HPAS in the logistic regression model (odds ratio = 3.7 [95% confidence interval: 1.1-13.6]). Daily inhaled corticosteroids (ICSs) + NS dose/m(2) predicted HPAS in the univariate logistic regression model (P = .038). Forced expiratory volume in 1 second/forced vital capacity <80% was associated with HPAS (odds ratio = 4.1 [95% confidence interval: 1.0-14.8]). Daily ICS + NS/m(2) dose was correlated with the postmetyrapone ACTH (r = -0.29, P < .001). BMI (P = .048) and percent adherence to ICS (P < .001) and NS (P = .002) were predictive of √postmetyrapone ACTH (R(2) = .176). CONCLUSIONS: Two-thirds of children on corticosteroids may have hypothalamic-pituitary-adrenal axis dysfunction. In one-third, central function had recovered but adrenal suppression persisted. Predictive factors for HPAS are NS use, BMI, and adherence to ICS and NS.

Hypothalamic-pituitary-adrenal axis suppression in asthmatic children on inhaled and nasal corticosteroids--more common than expected?

BACKGROUND: Hypothalamic pituitary adrenal axis suppression (HPAS) when treating asthmatic children with inhaled corticosteroids (ICS) is thought to be rare. OBJECTIVE: To determine the prevalence of HPAS in asthmatic children treated with ICS and nasal steroids (NS). METHODS: Twenty-six asthmatic children were recruited. Clinical features of HPAS, height, weight, height and weight velocity, steroid dose, adherence, symptom control and lung functions were documented. Metyrapone test was performed if the serum cortisol was > 83 nmol/L (> 3 microg/dL). RESULTS: No child had a serum cortisol < 83 nmol/L (< 3 microg/dL). Prevalence of HPAS was 35 (CI = 17%-56%). Daily NS dose/ m2 and cumulative NS dose/m2 were significantly (p = 0.03) inversely correlated with the post-metyrapone ACTH (r = -0.42 for both). Current ICS dose was not associated with the post-metyrapone ACTH (r = 0). There was a weak correlation with the daily ICS dose/m2 (r = -0.12) and cumulative ICS dose/m2 (r = -0.26). CONCLUSIONS: A third of asthmatic children on ICS and NS develop HPAS. Contributing factors are the use of NS, body size and cumulative dose of ICS.

Hypothalamic-pituitary-adrenal axis suppression in asthmatic children on inhaled and nasal corticosteroids: is the early-morning serum adrenocorticotropic hormone (ACTH) a useful screening test?

BACKGROUND: Hypothalamic-pituitary-adrenal axis suppression (HPAS) in asthmatic children treated with inhaled corticosteroids (ICS), with or without nasal steroids (NS), may be more common than previously thought. Only dynamic testing will identify children at risk of adrenal crisis. It is impractical to test all asthmatic children for HPAS with a gold standard adrenal function test, i.e. the metyrapone or insulin tolerance test. OBJECTIVE: To determine which clinical or biochemical parameter is the most useful screening test for HPAS in asthmatic children. METHODS: Twenty-six asthmatic children, 5-18 yr old, on ICS ± NS, not treated with oral or topical steroids in the preceding year were recruited. Height, weight, height velocity, weight velocity and a change in systolic blood pressure from the recumbent to the standing position (ΔSBP) were recorded. Early-morning urine for urinary free cortisol (UFC) and urinary cortisol metabolites (UCM) was collected. UFC was analysed by both a chemiluminescent assay and gas chromatography/mass spectrometry (GC-MS). Morning serum cortisol and adrenocorticotropic hormone (ACTH) levels were measured. The overnight metyrapone test was performed if the fasting morning serum cortisol was >83 nmol/l. HPAS was diagnosed if the ACTH failed to rise >100 pg/ml after metyrapone. Spearman correlation coefficients (r) were calculated between the post-metyrapone ACTH and each variable. A receiver-operating characteristics (ROC) curve was drawn for the most promising test, and the diagnostic performance was calculated. RESULTS: All clinical and biochemical parameters investigated were weakly and non-significantly correlated with the post-metyrapone ACTH, except for the morning serum ACTH (r = 0.68; p <0.001). The best discrimination between those who have and those who do not have HPAS is a morning serum ACTH level of 11.7 pg/ml. This corresponds to a sensitivity of 0.89 (0.57-0.98), a specificity of 0.77 (0.53-0.90), a positive predictive value of 0.67 (0.39-0.87), a negative predictive value of 0.93 (0.69-0.99), an accuracy of 0.81 (0.61-0.94), a positive likelihood ratio of 3.78 (1.68-9.49) and a negative likelihood ratio of 0.15 (0.03-0.60). CONCLUSIONS: The morning serum ACTH level was found to be the most useful screening test to detect HPAS in this sample of children receiving ICS ± NS. A larger study should be undertaken to refine the diagnostic precision of the morning serum ACTH level.

Hypothalamic-pituitary-adrenal axis suppression in asthmatic children on inhaled corticosteroids (Part 2)--the risk as determined by gold standard adrenal function tests: a systematic review.

The evidence for hypothalamic-pituitary-adrenal axis (HPA) suppression by inhaled corticosteroids (ICS) was found to be conflicting. Reviewers have not distinguished between gold standard and basal adrenal function tests. The utility of the latter is limited by physiological and pathological variability as well as by methodological concerns. The risk of HPA suppression in asthmatic children and adolescents treated with ICS, as determined by gold standard adrenal function tests, needs to be established. A systematic review of the literature from January 1973 to July 2005 was performed. The Medline and Cochrane databases were searched, the reference lists of retrieved articles were inspected and pharmaceutical companies were approached. Randomized-controlled trials, cohort and case-control studies designed to detect HPA suppression caused by ICS, diagnosed by the insulin tolerance test (ITT) or the metyrapone test, performed on asthmatics of all ages not on oral steroids, were included and assessed for methodological quality. Of the 22 identified studies only four met the criteria for inclusion. All of these were published before 1988 and only one was methodologically sound. The cohort study showed that the baseline risk for HPA suppression is 0% while the absolute risk is 100% in asthmatic children treated with a beclomethasone dipropionate metered dose inhaler at a dose of 250-600 mug/m(2)/day for 6-42 months. As suggested by other observations these results could be generalized to other ICS. They may be of clinical significance especially if children are subjected to stress. Further research is needed to establish the cumulative dose for all ICS at which HPA suppression will be precipitated. Guidelines for future trials are suggested.

Hypothalamic-pituitary-adrenal axis suppression in asthmatic children on inhaled corticosteroids: part 1. Which test should be used?

The effect of inhaled corticosteroids (ICS) on the hypothalamic-pituitary-adrenal axis (HPA) has been regarded as a 'benign physiological response'. A recent survey suggests that adrenal crisis might be more common in asthmatic children on ICS than previously thought. The clinical features of adrenal insufficiency are non-specific and can easily be missed. Accurate biochemical assessment of the axis is therefore mandatory. A review of the literature determined that all basal adrenal function tests, including plasma cortisol profiles, cannot identify which children can respond to stress. There is no evidence to suggests that the degree of the physiological adjustment of the HPA to ICS predicts clinically significant HPA suppression. Only gold standard adrenal function tests can assess the integrity of the whole axis. Of the two available tests, the correctly performed overnight metyrapone test (with ACTH levels) is safe and better by far. The use of cortisol profiles should only be used to demonstrate differences in systemic activity of various ICS and delivery devices. Regulatory bodies should insist on trials that evaluate the HPA with a gold standard adrenal function test before it is declared safe and allowed to be marketed. A re-analysis of studies that have utilized gold standard adrenal function tests only might identify the lowest safe dose and duration of ICS.