Heritability of fetal hemoglobin, white cell count, and other clinical traits from a sickle cell disease family cohort.

Sickle cell disease (SCD) is the most common monogenic disorder in the world. Notably, there is extensive clinical heterogeneity in SCD that cannot be fully accounted for by known factors, and in particular, the extent to which the phenotypic diversity of SCD can be explained by genetic variation has not been reliably quantified. Here, in a family-based cohort of 449 patients with SCD and 755 relatives, we first show that 5 known modifiers affect 11 adverse outcomes in SCD to varying degrees. We then utilize a restricted maximum likelihood procedure to estimate the heritability of 20 hematologic traits, including fetal hemoglobin (HbF) and white blood cell count (WBC), in the clinically relevant context of inheritance from healthy carriers to SCD patients. We report novel estimations of heritability for HbF at 31.6% (±5.4%) and WBC at 41.2% (±6.8%) in our cohort. Finally, we demonstrate shared genetic bases between HbF, WBC, and other hematologic traits, but surprisingly little overlap between HbF and WBC themselves. In total, our analyses show that HbF and WBC have significant heritable components among individuals with SCD and their relatives, demonstrating the value of using family-based studies to better understand modifiers of SCD.

Prevalence of hearing loss in pseudohypoparathyroidism.

BACKGROUND: The main clinical features of pseudohypoparathyroidism (PHP)/inactivating parathyroid hormone/parathyroid hormone-related protein signaling disorders (iPPSD), including parathyroid hormone (PTH) resistance, brachydactyly and short stature, develop during middle and late childhood. Very few studies have addressed hearing loss in PHP/iPPSD patients, and these studies have yielded widely divergent conclusions. The aim of our study was to assess hearing and determine the predictive factors of hearing loss in patients with PHP/iPPSD. METHODS: Our retrospective cohort study was conducted between March 2019 and May 2020 in the Otolaryngology Department and the calcium phosphate reference center for rare diseases in Bicêtre Paris-Saclay Hospital, France. We retrospectively collected data from patients with PHP/iPPSDs (age, sex, genetic mutations, height, body mass index (BMI), PTH resistance, presence or absence of ectopic ossifications and brachydactyly). All patients underwent auditory investigations, including tonal and vocal audiometry. The primary outcome was the pure tone average (PTA). The PTA was compared with the norm according to the International Organization for Standardization. Hearing loss was defined as a PTA ≥ 20 db. RESULTS: The median age of the patients was 15.6 years [9.5, 28.5]. Thirty-six patients were diagnosed with iPPSD2, and eight were diagnosed with iPPSD3. Twenty-six of them (59%) were female. Hearing impairment was confirmed in 17 patients (39%). The mean PTA and the mean SRT of the deaf ears were 40 ± 26 db and 31 ± 14 db. The mean difference in the PTA between the patients and the normal controls was 11.4 db (p = 0.00002). Short stature and the presence of ectopic ossifications were two significant predictive factors of hearing loss (p = 0.009 and p = 0.03, respectively). Sex, BMI, PTH resistance, mutation category and brachydactyly were not associated with an increased risk of hearing loss (p = 0.19, p = 0.41, p = 0.13, p = 0.50, p = 0.19, respectively). CONCLUSION: Our study confirmed the frequency of hearing loss in patients with PHP/iPPSD disease (prevalence = 39%). A diagnosis of PHP/iPPSD should trigger auditory investigations and follow-up, especially when short stature and/or ectopic ossifications are present.

Characterization of Digestive Manifestations in Patients with Impaired PTH/PTHrP Signaling Disorder/Pseudohypoparathyroidism.

INTRODUCTION: Pseudohypoparathyroidism, newly classified as inactivating PTH/PTHrP signaling disorder (iPPSD) type 2 or type 3, is a rare disease caused by defects in the GNAS imprinted gene that encodes Gsα. The most common phenotype comprises resistance to hormones binding to G protein-coupled receptors such as PTH, PTHrP, or TSH, subcutaneous ossifications, short stature, brachydactyly, and early onset obesity. Uncommon features have been described including sleep apnea, asthma, and resistance to calcitonin. At the national French reference center for rare calcium and phosphate metabolism diseases, a large cohort of patients with iPPSD type 2 and type 3 is followed. Interestingly, digestive manifestations and in particular intractable constipation were regularly reported by families of children with iPPSD type 2 or type 3. OBJECTIVE: The aim of our study was therefore to specify the frequency and characteristics of digestive manifestations in children followed up for iPPSD2 or iPPSD3 in our reference center. MATERIAL AND METHODS: Thirty-six patients aged between 2 and 18 years (32 followed up for iPPSD2 and 4 for iPPSD3) were included. Parents completed a specific questionnaire to assess any digestive disorders in their child. The diagnosis of constipation was established using the Bristol visual scale in the event of a score of less than 2 according to stool appearance. RESULTS: Parents reported constipation through the questionnaires in 22/36 (over 60%) of the children. It was the most frequently reported digestive disorder. Among these 22 children, 19 (87%) had a Bristol score for stool shape and texture between 1 and 2 on a scale of 7, confirming constipation. Dedicated treatment had been initiated for 10 (55%) of them, yet only 3 families (16%) considered this treatment effective. Neonatal vomiting and eating disorders, such as lack of satiety or food selectivity, were also noted in 18 (50%) of patients, as was gastroesophageal reflux present in the neonatal period in 14 (40%) of children. There were no significant differences according to the type of iPPSD or patient age. CONCLUSION: Our work shows for the first time that digestive manifestations, including constipation, occur frequently in children followed for iPPSD, suggesting a potential role of Gsα and G protein receptors in the digestive tract. It is well known that constipation and digestive symptoms alter quality of life. Early management is therefore essential to improve the quality of life of children followed for iPPSD. Our data need to be confirmed on a larger cohort.

High prevalence of hypercalcitoninemia in a large cohort of adult and paediatric patients with PTH resistance syndromes.

BACKGROUND: Pseudohypoparathyroidism (PHP) refers to a group of rare hereditary disorders associated with resistance to parathormone (PTH) and other hormones now termed inactivating PTH/PTHrP disorders (iPPSD). Hypercalcitoninemia has been seldom reported in small series. Our aim was to investigate the characteristics of hypercalcitoninemia in paediatric and adult patients with PHP/iPPSD. METHODS: We retrospectively collected data from two cohorts from two European Endocrinology tertiary centers: the paediatric cohort comprised 88 children with available calcitonin (CT) measurements; the adult cohort included 43 individuals with simultaneous CT and PTH measurements. RESULTS: In the paediatric cohort 65.9% had hypercalcitoninemia (median CT 15 ng/L); in the adult cohort 53.5% (mean CT 21.6 ng/L). There was no difference between CT in paediatric and adult population; we observed stable CT levels over a median follow-up of 134.5 months in adults. Notably, no correlations were detected between CT and PTH levels. Other etiologies of hypercalcitoninemia were excluded, adult patients underwent regular thyroid ultrasound (US) to screen for medullary thyroid cancer (MTC). We performed 20 calcium stimulation tests in adult patients. While there was a significant difference in basal and peak CT between our patients, healthy subjects and subjects with MTC, there was no difference with patients with C-cell hyperplasia. CONCLUSIONS: This study underscores the common occurrence of hypercalcitoninemia in both paediatric and adult PHP/iPPSD patients, in particular with subtypes iPPSD2-iPPSD3. Furthermore, these patients show an hyperresponsiveness to calcium stimulation test falling between healthy subjects and patients with MTC. These findings contribute into the understanding of CT dynamics in the context of PHP/iPPSD.

Neonatal and Early Infancy Features of Patients With Inactivating PTH/PTHrP Signaling Disorders/Pseudohypoparathyroidism.

BACKGROUND: Pseudohypoparathyroidism (PHP) and related disorders newly referred to as inactivating PTH/PTHrP signaling disorders (iPPSD) are rare endocrine diseases. Many clinical features including obesity, neurocognitive impairment, brachydactyly, short stature, parathyroid hormone (PTH) resistance, and resistance to other hormones such as thyroid-stimulating hormone (TSH) have been well described, yet they refer mainly to the full development of the disease during late childhood and adulthood. OBJECTIVE: A significant delay in diagnosis has been reported; therefore, our objective is to increase awareness on neonatal and early infancy presentation of the diseases. To do so, we analyzed a large cohort of iPPSD/PHP patients. METHODS: We included 136 patients diagnosed with iPPSD/PHP. We retrospectively collected data on birth and investigated the rate of neonatal complications occurring in each iPPSD/PHP category within the first month of life. RESULTS: Overall 36% of patients presented at least one neonatal complication, far more than the general population; when considering only the patients with iPPSD2/PHP1A, it reached 47% of the patients. Neonatal hypoglycemia and transient respiratory distress appeared significantly frequent in this latter group, ie, 10.5% and 18.4%, respectively. The presence of neonatal features was associated with earlier resistance to TSH (P < 0.001) and with the development of neurocognitive impairment (P = 0.02) or constipation (P = 0.04) later in life. CONCLUSION: Our findings suggest that iPPSD/PHP and especially iPPSD2/PHP1A newborns require specific care at birth because of an increased risk of neonatal complications. These complications may predict a more severe course of the disease; however, they are unspecific which likely explains the diagnostic delay.

Combined gait analysis and radiologic examination in children with X-linked hypophosphatemia.

BACKGROUND: X-linked hypophosphataemia causes bone deformities and gait abnormalities that tend to worsen with age in the absence of appropriate treatment. However, doctors do not currently use quantitative tools to characterize these symptoms and their possible interactions. METHODS: Radiographs and 3D gait data from 43 non-surgical growing children with X-linked hypophosphataemia were acquired prospectively. Data from age-matched typically developing children were used to form the reference group. Subgroups based on radiological parameters were compared with each other and with the reference population. Linear correlations between radiographic parameters and gait variables were examined. FINDING: X-linked hypophosphatemic patients differed from the control group in pelvic tilt, ankle plantarflexion, knee flexion moment and power. High correlations with tibiofemoral angle were found for trunk lean, knee and hip adduction, and knee abduction moment. The Gait Deviation Index was below 80 for 88% of the patients with a high tibiofemoral angle (varus). Compared to other subgroups, varus patients had augmented trunk lean (+3°) and knee adduction (+10°) and decreased hip adduction (-5°) and ankle plantarflexion (-6°). Femoral torsion was associated with alterations in rotation at the knee, and hip. INTERPRETATION: Gait abnormalities induced in X-linked hypophosphataemia have been described in a large cohort of children. Links between gait alterations and lower limb deformities were found, with varus deformities standing out. Since bony deformities appear when X-linked hypophosphatemic children start walking and have been found to alter gait patterns, we suggest that combining radiology with gait analysis may improve the clinical management of X-linked hypophosphataemia.

Quantitative analysis of lower limb and pelvic deformities in children with X-linked hypophosphatemic rickets.

INTRODUCTION: X-linked hypophosphatemia (XLH) rickets mainly causes leg deformities in children that can worsen as they grow. We hypothesized that quantifying the bone parameters will help to document and monitor these deformities in children with XLH. METHODS: Thirty-five growing children affected by XLH were included in this cross-sectional study. Biplanar radiographs were taken with an EOS system allowing three-dimensional (3D) reconstructions of the pelvis and legs. Sixteen geometric parameters were calculated for the legs and pelvis. A control group of 40 age-matched patients was used to define the reference values for these geometric parameters. RESULTS: For the legs, significant differences (p<0.05) appeared between the XLH patients and the control group in the neck-shaft angle, femur/tibia length ratio and HKS. Among the 70 legs in the XLH group, 23 were in genu varum, 25 were in genu valgum and 22 were straight. There were significant differences between the genu varum and genu valgum subgroups in the femoral mechanical angle and the HKS. A strong correlation was found between the femoral mechanical angle and femorotibial angle (r2=0.73) and between the femoral mechanical angle and HKS (r2=0.69) The sacral slope and acetabular anteversion were significant different from the reference values. DISCUSSION: Quantitative radiological parameters derived from 3D reconstructions show that the deformities in XLH patients are (1) mainly in - but not limited to - the femoral shaft; (2) highly variable from one person to another. Some of these radiological parameters may be useful for the diagnosis and monitoring of XLH patients. LEVEL OF EVIDENCE: III; case control study.

Recombinant growth hormone improves growth and adult height in patients with maternal inactivating GNAS mutations.

BACKGROUND: Maternal inactivating GNAS mutations lead to pseudohypoparathyroidism 1A (PHP1A), newly classified as inactivating parathyroid hormone (PTH)/PTHrP-signaling disorder type 2 of maternal inheritance (iPPSD2). Patients present with resistance to PTH and other hormones, subcutaneous ossifications, brachydactyly, short stature, and early-onset obesity. They can be born small for gestational age (SGA) and may present with growth hormone (GH) deficiency. The use of recombinant human GH (rhGH) therapy has been sporadically reported, yet we lack data on the long-term efficacy and safety of rhGH, as well as on adult height. OBJECTIVE: Our multicenter, retrospective, observational study describes growth in patients treated with rhGH in comparison with untreated iPPSD2/PHP1A controls. METHODS: We included 190 patients, of whom 26 received rhGH. Height, weight, body mass index at various time points, and adult height were documented. We analyzed the effect of rhGH on adult height by using linear mixed models. RESULTS: Adult height was available for 11/26 rhGH-treated individuals and for 69/164 controls. Patients treated with rhGH showed a gain in height of 0.7 standard deviation scores (SDS) after 1 year (CI +0.5 to +0.8, P < .001) and of 1.5 SDS after 3 years (CI +1.0 to +2.0, P < .001). Additionally, there was a clear beneficial impact of rhGH on adult height when compared with untreated controls, with a difference of 1.9 SDS (CI +1.1 to +2.7, P < .001). Body mass index SDS did not vary significantly upon rhGH therapy. CONCLUSION: Recombinant human growth hormone treatment of iPPSD2/PHP1A patients with short stature improves growth and adult height. More studies are needed to confirm long-term efficacy and safety.

Adult height improved over decades in patients with X-linked hypophosphatemia: a cohort study.

OBJECTIVES: The aim of this study is to analyze height after cessation of growth (final height [FH]) and its evolution over the last decades in X-linked hypophosphatemia (XLH) patients in France, as the data on natural history of FH in XLH are lacking. DESIGN: We performed a retrospective observational study in a large cohort of French XLH patients with available data on FH measurements. MATERIALS AND METHODS: We divided patients into 3 groups according to their birth year: group 1 born between 1950 and 1974, group 2 born between 1975 and 2000, and group 3 born between 2001 and 2006, respectively, and compared their FHs. RESULTS: A total of 398 patients were included. Mean FHs were the following: for group 1, -2.31 ± 1.11 standard deviation score (SDS) (n = 127), 156.3 ± 9.7 cm in men and 148.6 ± 6.5 cm in women; for group 2, -1.63 ± 1.13 SDS (n = 193), 161.6 ± 8.5 cm in men and 153.1 ± 7.2 cm in women; and for group 3, -1.34 ± 0.87 SDS (n = 78), 165.1 ± 5.5 cm in men and 154.7 ± 6 cm in women. We report a significant increase in mean FH SDS over 3 generations of patients, for both men and women (P < .001). Final height SDS in male (-2.08 ± 1.18) was lower than in female (-1.70 ± 1.12) (P = .002). CONCLUSION: The FH of XLH patients in France increased significantly over the last decades. Even though men's FHs improved more than women's, men with XLH remain shorter reflecting a more severe disease phenotype. While the results are promising, most patients with XLH remain short leaving room for improvement.

Prospective Analysis of Muscle Adiposity in Children With X-linked Hypophosphatemic Rickets vs Control Children.

Context: Children with X-linked hypophosphatemic (XLH) rickets have muscle weakness that severely impairs their function. Intermuscular and intramuscular adipose tissue (IMAT and intraMAT, respectively) may contribute to this muscle weakness. Objective: This work aimed to compare IMAT and intraMAT in XLH children vs typically developing (TD) children. Methods: A prospective, monocentric cohort study was conducted of XLH (n = 11; aged 10.3 years [6-17]) and TD children (n = 22; aged 10.2 years [5-15.5]). All children underwent magnetic resonance imaging of the lower limbs; IMAT and intraMAT percentages were calculated after manual contouring of each muscle of the thigh and the deep fascia at mid-thigh level. Results: XLH children were comparable in age but shorter and heavier than TD children (P = .001 and P = .03, respectively). They had smaller muscle length and volume than TD children (P < .001) but there was no statistically significant difference in muscle cross-sectional area between the groups (P = .833). The total percentage of IMAT was higher in XLH children (8.66% vs 3.60% in TD children; P < .0001). In addition, though the total percentage of intraMAT did not differ significantly (12.58% and 10.85% in XLH and TD children, respectively; P = .143) intraMAT was statistically significantly higher in XLH children than TD children in 4 of the 13 muscles studied. Conclusion: Our results show that IMAT is higher in young children with XLH, independently of obesity and overweight. Further, these results will facilitate both the early prevention of functional and metabolic consequences of the increase in adipose tissue in XLH children.

Growth pattern in children with X-linked hypophosphatemia treated with burosumab and growth hormone.

BACKGROUND: X-linked hypophosphatemia (XLH) is characterized by increased serum concentrations of fibroblast growth factor 23 (FGF23), hypophosphatemia and insufficient endogenous synthesis of calcitriol. Beside rickets, odonto- and osteomalacia, disproportionate short stature is seen in most affected individuals. Vitamin D analogs and phosphate supplements, i.e., conventional therapy, can improve growth especially when started early in life. Recombinant human growth hormone (rhGH) therapy in XLH children with short stature has positive effects, although few reports are available. Newly available treatment (burosumab) targeting increased FGF23 signaling leads to minimal improvement of growth in XLH children. So far, we lack data on the growth of XLH children treated with concomitant rhGH and burosumab therapies. RESULTS: Thirty-six patients received burosumab for at least 1 year after switching from conventional therapy. Of these, 23 received burosumab alone, while the others continued rhGH therapy after switching to burosumab. Children treated with burosumab alone showed a minimal change in height SDS after 1 year (mean ± SD 0.0 ± 0.3 prepubertal vs. 0.1 ± 0.3 pubertal participants). In contrast, rhGH clearly improved height during the first year of treatment before initiating burosumab (mean ± SD of height gain 1.0 ± 0.4); patients continued to gain height during the year of combined burosumab and rhGH therapies (mean ± SD height gain 0.2 ± 0.1). As expected, phosphate serum levels normalized upon burosumab therapy. No change in serum calcium levels, urinary calcium excretion, or 25-OHD levels was seen, though 1,25-(OH)2D increased dramatically under burosumab therapy. CONCLUSION: To our knowledge, this is the first study on growth under concomitant rhGH and burosumab treatments. We did not observe any safety issue in this cohort of patients which is one of the largest in Europe. Our data suggest that continuing treatment with rhGH after switching from conventional therapy to burosumab, if the height prognosis is compromised, might be beneficial for the final height.

Tubular Acidification Defect in Adults with Sickle Cell Disease.

BACKGROUND AND OBJECTIVES: Metabolic acidosis is a frequent manifestation of sickle cell disease but the mechanisms and determinants of this disorder are unknown. Our aim was to characterize urinary acidification capacity in adults with sickle cell disease and to identify potential factors associated with decreased capacity to acidify urine. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Among 25 adults with sickle cell disease and an eGFR of ≥60 ml/min per 1.73 m2 from a single center in France, we performed an acute acidification test after simultaneous administration of furosemide and fludrocortisone. A normal response was defined as a decrease in urinary pH <5.3 and an increase in urinary ammonium excretion ≥33 µEq/min at one or more of the six time points after furosemide and fludrocortisone administration. RESULTS: Of the participants (median [interquartile range] age of 36 [24-43] years old, 17 women), 12 had a normal and 13 had an abnormal response to the test. Among these 13 participants, nine had normal baseline plasma bicarbonate concentration. Plasma aldosterone was within the normal range for all 13 participants with an abnormal response, making the diagnosis of type 4 tubular acidosis unlikely. The participants with an abnormal response to the test were significantly older, more frequently treated with oral bicarbonate, had a higher plasma uric acid concentration, higher hemolysis activity, lower eGFR, lower baseline plasma bicarbonate concentration, higher urine pH, lower urine ammonium ion excretion, and lower fasting urine osmolality than those with a normal response. Considering both groups, the maximum urinary ammonium ion excretion was positively correlated with fasting urine osmolality (r2=0.34, P=0.002), suggesting that participants with sickle cell disease and lower urine concentration capacity have lower urine acidification capacity. CONCLUSIONS: Among adults with sickle cell disease, impaired urinary acidification capacity attributable to distal tubular dysfunction is common and associated with the severity of hyposthenuria. PODCAST: This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_12_10_CJN07830719.mp3.

Physiological Evaluation for Endurance Exercise Prescription in Sickle Cell Disease.

PURPOSE: Although strenuous exercise may expose sickle cell disease (SCD) patients to risks of vaso-occlusive crisis, evidence suggests that regular endurance exercise may be beneficial. This study aimed to test (i) the safety and usefulness of a submaximal incremental exercise in evaluating physical ability of SCD patients and identify a marker for the management of endurance exercise and (ii) the feasibility of endurance exercise sessions in SCD patients. METHODS: Twenty adults with SCD (12 men and 8 women) performed a submaximal incremental exercise used to determine the first lactate threshold (LT1) and stopped as soon as blood lactate concentration ([lactate]b) reached ≥4 mmol·L. Fifteen of those patients (8 men and 7 women) also performed three 30-min endurance exercise sessions at ~2.5 mmol·L of [lactate]b on separate occasions. RESULTS: LT1 occurred at 47 ± 3 and 33 ± 3 W for men and women, respectively, demonstrating the extreme deconditioning and, thus, low physical ability of adult SCD patients. During endurance exercise, peripheral oxygen saturation and [lactate]b most often remained stable and within acceptable ranges. CONCLUSIONS: The proposed strategy of submaximal incremental exercise allowed safe determination of LT1, an important parameter of patients' physical ability. The study also demonstrated the feasibility and safety of individually tailored endurance exercises at ~2.5 mmol·L of [lactate]b. These latter results suggest that endurance training programs may be considered for adult SCD patients and that the method proposed here may be helpful in that regard.

Score Predicting Acute Chest Syndrome During Vaso-occlusive Crises in Adult Sickle-cell Disease Patients.

BACKGROUND: Vaso-occlusive crisis (VOC), hallmark of sickle-cell disease (SCD), is the first cause of patients' Emergency-Room admissions and hospitalizations. Acute chest syndrome (ACS), a life-threatening complication, can occur during VOC, be fatal and prolong hospitalization. No predictive factor identifies VOC patients who will develop secondary ACS. METHODS: This prospective, monocenter, observational study on SS/S-ß0thalassemia SCD adults aimed to identify parameters predicting ACS at Emergency-Department arrival. The primary endpoint was ACS onset within 15days of admission. Secondary endpoints were hospitalization duration, morphine consumption, pain evaluation, blood transfusion(s) (BT(s)), requiring intensive care and mortality. FINDINGS: Among 250 VOCs included, 247 were analyzed. Forty-four (17.8%) ACSs occurred within 15 (median [IQR] 3 [2, 3]) days post-admission based on auscultation abnormalities; missing chest radiographs excluded three patients. Comparing ACS to VOC, respectively, median hospital stay was longer 9 [7-11] vs 4 [3-7] days (p<0.0001), 7/41 (17%) vs 1/203 (0.5%) required intensive care (p<0.0001), and 20/41 (48.7%) vs 6/203 (3%) required BTs (p<0.0001). No patient died. The multivariate model retained reticulocyte and leukocyte counts, and spine and/or pelvis pain as being independently associated with ACS; the resulting ACS-predictive score's area under the ROC was 0.840 [95% CI 0.780-0.900], 98.8% negative-predictive value and 39.5% positive-predictive value for the real ACS incidence. INTERPRETATION: The ACS-predictive score is simple, easily applied and could change VOC management and therapeutic perspectives. Assessed ACS risk could lead to earlier discharges or close monitoring and rapid medical intensification to prevent ACS.