Diverse genetic aetiologies and clinical outcomes of paediatric hypoparathyroidism

Further delineation of phenotype and genotype of Kenny-Caffey syndrome type 2 (phenotype and genotype of KCS type 2)

BACKGROUND

Kenny-Caffey syndrome type 2 (KCS2) is an extremely rare inherited disorder characterized by proportionate short stature, skeletal defects, ocular and dental abnormalities, and transient hypocalcemia. It is caused by variants in FAM111A gene. Diagnosis of KCS2 can be challenging because of its similarities to other syndromes, the absence of clear hallmarks and the deficient number of genetically confirmed cases. Here, we aimed to further delineate and summarize the genotype and phenotype of KCS2, in order to get a better understanding of this rare disorder, and promote early diagnosis and intervention.

METHODS

We present clinical and genetic characteristics of eight newly affected individuals with KCS2 from six families, including one family with three individuals found to be a father-to-daughter transmission, adding to the limited literature. Furthermore, we performed a review of genetically confirmed KCS2 cases in PubMed, MEDLINE and CNKI databases.

RESULTS

There were six females and two males in our cohort. All the patients presented with short stature (100.0%). Clinical manifestations included ocular defects such as hypermetropia (5/8), dental problems such as defective dentition (3/8) and dental caries (3/8), skeletal and brain anomalies such as delayed closure of anterior fontanelle (6/8), cerebral calcification (3/8), cortical thickening (3/8) and medullary stenosis (4/8) of tubular bones. Endocrinologic abnormalities included hypoparathyroidism (5/8) and hypocalcemia (3/8). One male patient had micropenis and microorchidism. All cases harboured missense variants of FAM111A, and nucleotides c.1706 arose as a mutational hotspot, with seven individuals harbouring a c.1706G>A (p.Arg569His) variant, and one child harbouring a c.1531T>C (p.Tyr511His) variant. Literature review yielded a total of 46 patients from 20 papers. Data analysis showed that short stature, hypoparathyroidism and hypocalcemia, ocular and dental defects, skeletal features including cortical thickening and medullary stenosis of tubular bones, and seizures/spasms were present in more than 70% of the reported KCS2 cases.

CONCLUSION

We provide detailed characteristics of the largest KCS2 group in China and present the first genetically confirmed instance of father-to-daughter transmission of KCS2. Our study confirms that Arg569His is the hot spot variant and summarizes the typical phenotypes of KCS2, which would help early diagnosis and intervention.

Unravelling the Intricate Roles of FAM111A and FAM111B: From Protease-Mediated Cellular Processes to Disease Implications

Proteases are critical enzymes in cellular processes which regulate intricate events like cellular proliferation, differentiation and apoptosis. This review highlights the multifaceted roles of the serine proteases FAM111A and FAM111B, exploring their impact on cellular functions and diseases. FAM111A is implicated in DNA replication and replication fork protection, thereby maintaining genome integrity. Additionally, FAM111A functions as an antiviral factor against DNA and RNA viruses. Apart from being involved in DNA repair, FAM111B, a paralog of FAM111A, participates in cell cycle regulation and apoptosis. It influences the apoptotic pathway by upregulating anti-apoptotic proteins and modulating cell cycle-related proteins. Furthermore, FAM111B's association with nucleoporins suggests its involvement in nucleo-cytoplasmic trafficking and plays a role in maintaining normal telomere length. FAM111A and FAM111B also exhibit some interconnectedness and functional similarity despite their distinct roles in cellular processes and associated diseases resulting from their dysfunction. FAM111A and FAM111B dysregulation are linked to genetic disorders: Kenny-Caffey Syndrome type 2 and Gracile Bone Dysplasia for FAM111A and POIKTMP, respectively, and cancers. Therefore, the dysregulation of these proteases in diseases emphasizes their potential as diagnostic markers and therapeutic targets. Future research is essential to unravel the intricate mechanisms governing FAM111A and FAM111B and explore their therapeutic implications comprehensively.

Expanding the Phenotypic Spectrum of Kenny-Caffey Syndrome

CONTEXT

Kenny-Caffey syndrome (KCS) is a rare hereditary disorder characterized by short stature, hypoparathyroidism, and electrolyte disturbances. KCS1 and KCS2 are caused by pathogenic variants in TBCE and FAM111A, respectively. Clinically the phenotypes are difficult to distinguish.

OBJECTIVE

The objective was to determine and expand the phenotypic spectrum of KCS1 and KCS2 in order to anticipate complications that may arise in these disorders.

METHODS

We clinically and genetically analyzed 10 KCS2 patients from 7 families. Because we found unusual phenotypes in our cohort, we performed a systematic review of genetically confirmed KCS cases using PubMed and Scopus. Evaluation by 3 researchers led to the inclusion of 26 papers for KCS1 and 16 for KCS2, totaling 205 patients. Data were extracted following the Cochrane guidelines and assessed by 2 independent researchers.

RESULTS

Several patients in our KCS2 cohort presented with intellectual disability (3/10) and chronic kidney disease (6/10), which are not considered common findings in KCS2. Systematic review of all reported KCS cases showed that the phenotypes of KCS1 and KCS2 overlap for postnatal growth retardation (KCS1: 52/52, KCS2: 23/23), low parathyroid hormone levels (121/121, 16/20), electrolyte disturbances (139/139, 24/27), dental abnormalities (47/50, 15/16), ocular abnormalities (57/60, 22/23), and seizures/spasms (103/115, 13/16). Symptoms more prevalent in KCS1 included intellectual disability (74/80, 5/24), whereas in KCS2 bone cortical thickening (1/18, 16/20) and medullary stenosis (7/46, 27/28) were more common.

CONCLUSION

Our case series established chronic kidney disease as a new feature of KCS2. In the literature, we found substantial overlap in the phenotypic spectra of KCS1 and KCS2, but identified intellectual disability and the abnormal bone phenotype as the most distinguishing features.

Challenges in establishing animal models for studying osteoimmunology of hypoparathyroidism

Hypoparathyroidism is a relatively rare human and veterinary disease characterized by deficient or absent production of parathyroid hormone (PTH). PTH is known as a classical regulator of calcium and phosphorus homeostasis. Nevertheless, the hormone also appears to modulate immune functions. For example, increased CD4:CD8 T-cell ratios and elevated interleukin (IL)-6 and IL-17A levels were observed in patients with hyperparathyroidism, whereas gene expression of tumor necrosis factor-α (TNF-α) and granulocyte macrophage-colony stimulating factor (GM-CSF) was decreased in patients with chronic postsurgical hypoparathyroidism. Various immune cell populations are affected differently. So, there is a need for validated animal models for the further characterization of this disease for identifying targeted immune-modulatory therapies. In addition to genetically modified mouse models of hypoparathyroidism, there are surgical rodent models. Parathyroidectomy (PTX) can be well performed in rats-for pharmacological and associated osteoimmunological research and bone mechanical studies, a large animal model could be preferable, however. A major drawback for successfully performing total PTX in large animal species (pigs and sheep) is the presence of accessory glands, thus demanding to develop new approaches for real-time detection of all parathyroid tissues.

Case report: Late middle-aged features of FAM111A variant, Kenny-Caffey syndrome type 2-suggestive symptoms during a long follow-up

Kenny-Caffey syndrome type 2 (KCS2) is an extremely rare skeletal disorder involving hypoparathyroidism and short stature. It has an autosomal dominant pattern of inheritance and is caused by variants in the FAM111 trypsin-like peptidase A (FAM111A) gene. This disease is often difficult to diagnose due to a wide range of more common diseases manifesting hypoparathyroidism and short stature. Herein, we present the case of a 56-year-old female patient with idiopathic hypoparathyroidism and a short stature. The patient was treated for these conditions during childhood. Upon re-evaluating the etiology of KCS2, we suspected that the patient had the disorder because of clinical manifestations, such as cortical thickening and medullary stenosis of the bones, and lack of intellectual abnormalities. Genetic testing identified a heterozygous missense variant in the FAM111A gene (p.R569H). Interestingly, the patient also had bilateral sensorineural hearing loss and vestibular dysfunction, which have been rarely described in previous reports of pediatric cases. In KCS2, inner ear dysfunction due to Eustachian tube dysfunction may progress in middle age or later. However, this disease is now being reported in younger patients. Nevertheless, our case may be instructive of how such cases emerge chronically after middle age. Herein, we also provide a literature review of KCS2.

Functions and evolution of FAM111 serine proteases

Proteolysis plays fundamental and regulatory roles in diverse cellular processes. The serine protease FAM111A (FAM111 trypsin-like peptidase A) emerged recently as a protease involved in two seemingly distinct processes: DNA replication and antiviral defense. FAM111A localizes to nascent DNA and plays a role at the DNA replication fork. At the fork, FAM111A is hypothesized to promote DNA replication at DNA-protein crosslinks (DPCs) and protein obstacles. On the other hand, FAM111A has also been identified as a host restriction factor for mutants of SV40 and orthopoxviruses. FAM111A also has a paralog, FAM111B, a serine protease with unknown cellular functions. Furthermore, heterozygous missense mutations in FAM111A and FAM111B cause distinct genetic disorders. In this review, we discuss possible models that could explain how FAM111A can function as a protease in both DNA replication and antiviral defense. We also review the consequences of FAM111A and FAM111B mutations and explore possible mechanisms underlying the diseases. Additionally, we propose a possible explanation for what drove the evolution of FAM111 proteins and discuss why some species have two FAM111 proteases. Altogether, studies of FAM111 proteases in DNA repair, antiviral defense, and genetic diseases will help us elucidate their functions and the regulatory mechanisms.

Management of Hypoparathyroidism

Hypoparathyroidism (HypoPT) is a rare disorder characterized by hypocalcemia in the presence of a low or inappropriately normal parathyroid hormone level. HypoPT is most commonly seen after neck surgery, which accounts for approximately 75% of cases, whereas approximately 25% have HypoPT due to nonsurgical causes. In both groups of patients, conventional therapy includes calcium and active vitamin D analogue therapy aiming to maintain serum calcium concentration in the low normal or just below the normal reference range and normalize serum phosphorus, magnesium concentrations, and urine calcium levels. The limitations of conventional therapy include wide fluctuations in serum calcium, high pill burden, poor quality of life, and renal complications. Parathyroid hormone (PTH) replacement therapy may improve the biochemical profile in those in whom conventional therapy proves unsatisfactory. Based on a systematic review and meta-analysis of the literature, the panel made a graded recommendation suggesting conventional therapy as first line therapy rather than administration of PTH (weak recommendation, low quality evidence). When conventional therapy is deemed unsatisfactory, the panel considers use of PTH. Because pregnancy and lactation are associated with changes in calcium homeostasis, close monitoring is required during these periods with appropriate adjustment of calcium and active vitamin D analogue therapy to ensure that serum calcium remains in the mid to low normal reference range in order to avoid maternal and fetal complications. Emerging therapies include molecules with prolonged PTH action as well as different mechanisms of action that may significantly enhance drug efficacy and safety. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Complications, Symptoms, Presurgical Predictors in Patients With Chronic Hypoparathyroidism: A Systematic Review

The complications and symptoms of hypoparathyroidism remain incompletely defined. Measuring serum parathyroid hormone (PTH) and calcium levels early after total thyroidectomy may predict the development of chronic hypoparathyroidism. The study aimed (i) to identify symptoms and complications associated with chronic hypoparathyroidism and determine the prevalence of those symptoms and complications (Part I), and (ii) to examine the utility of early postoperative measurements of PTH and calcium in predicting chronic hypoparathyroidism (Part II). We searched Medline, Medline In-Process, EMBASE, and Cochrane CENTRAL to identify complications and symptoms associated with chronic hypoparathyroidism. We used two predefined criteria (at least three studies reported the complication and symptom and had statistically significantly greater pooled relative estimates). To estimate prevalence, we used the median and interquartile range (IQR) of the studies reporting complications and symptoms. For testing the predictive values of early postoperative measurements of PTH and calcium, we used a bivariate model to perform diagnostic test meta-analysis. In Part I, the 93 eligible studies enrolled a total of 18,973 patients and reported on 170 complications and symptoms. We identified nine most common complications or symptoms probably associated with chronic hypoparathyroidism. The complications or symptoms and the prevalence are as follows: nephrocalcinosis/nephrolithiasis (median prevalence among all studies 15%), renal insufficiency (12%), cataract (17%), seizures (11%), arrhythmia (7%), ischemic heart disease (7%), depression (9%), infection (11%), and all-cause mortality (6%). In Part II, 18 studies with 4325 patients proved eligible. For PTH measurement, regarding the posttest probability, PTH values above 10 pg/mL 12-24 hours postsurgery virtually exclude chronic hypoparathyroidism irrespective of pretest probability (100%). When PTH values are below 10 pg/mL, posttest probabilities range from 3% to 64%. Nine complications and symptoms are probably associated with chronic hypoparathyroidism. A PTH value above a threshold of 10 pg/mL 12-24 hours after total thyroidectomy is a strong predictor that the patients will not develop chronic hypoparathyroidism. Patients with PTH values below the threshold need careful monitoring as some will develop chronic hypoparathyroidism. © 2022 American Society for Bone and Mineral Research (ASBMR).

Etiology and Pathophysiology of Hypoparathyroidism: A Narrative Review

The approach utilized a systematic review of the medical literature executed with specifically designed criteria that focused on the etiologies and pathogenesis of hypoparathyroidism. Enhanced attention by endocrine surgeons to new knowledge about parathyroid gland viability are reviewed along with the role of intraoperative parathyroid hormone (ioPTH) monitoring during and after neck surgery. Nonsurgical etiologies account for a significant proportion of cases of hypoparathyroidism (~25%), and among them, genetic etiologies are key. Given the pervasive nature of PTH deficiency across multiple organ systems, a detailed review of the skeletal, renal, neuromuscular, and ocular complications is provided. The burden of illness on affected patients and their caregivers contributes to reduced quality of life and social costs for this chronic endocrinopathy. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Genetics of monogenic disorders of calcium and bone metabolism

Disorders of calcium homeostasis are the most frequent metabolic bone and mineral disease encountered by endocrinologists. These disorders usually manifest as primary hyperparathyroidism (PHPT) or hypoparathyroidism (HP), which have a monogenic aetiology in 5%-10% of cases, and may occur as an isolated endocrinopathy, or as part of a complex syndrome. The recognition and diagnosis of these disorders is important to facilitate the most appropriate management of the patient, with regard to both the calcium-related phenotype and any associated clinical features, and also to allow the identification of other family members who may be at risk of disease. Genetic testing forms an important tool in the investigation of PHPT and HP patients and is usually reserved for those deemed to be an increased risk of a monogenic disorder. However, identifying those suitable for testing requires a thorough clinical evaluation of the patient, as well as an understanding of the diversity of relevant phenotypes and their genetic basis. This review aims to provide an overview of the genetic basis of monogenic metabolic bone and mineral disorders, primarily focusing on those associated with abnormal calcium homeostasis, and aims to provide a practical guide to the implementation of genetic testing in the clinic.

FAM111A is dispensable for electrolyte homeostasis in mice

Autosomal dominant mutations in FAM111A are causative for Kenny-Caffey syndrome type 2. Patients with Kenny-Caffey syndrome suffer from severe growth retardation, skeletal dysplasia, hypoparathyroidism, hypocalcaemia, hyperphosphataemia and hypomagnesaemia. While recent studies have reported FAM111A to function in antiviral response and DNA replication, its role in regulating electrolyte homeostasis remains unknown. In this study, we assessed the role of FAM111A in the regulation of serum electrolyte balance using a Fam111a knockout (Fam111a-/-) C57BL/6 N mouse model. Fam111a-/- mice displayed normal weight and serum parathyroid hormone (PTH) concentration and exhibited unaltered magnesium, calcium and phosphate levels in serum and 24-hour urine. Expression of calciotropic (including Cabp28k, Trpv5, Klotho and Cyp24a1), magnesiotropic (including Trpm6, Trpm7, Cnnm2 and Cnnm4) and phosphotropic (Slc20a1, Slc20a2, Slc34a1 and Slc34a3) genes in the kidneys, duodenum and colon were not affected by Fam111a depletion. Only Slc34a2 expression was significantly upregulated in the duodenum, but not in the colon. Analysis of femurs showed unaffected bone morphology and density in Fam111a-/- mice. Kidney and parathyroid histology were also normal in Fam111a-/- mice. In conclusion, our study is the first to characterise the function of FAM111A in vivo and we report that mice lacking FAM111A exhibit normal electrolyte homeostasis on a standard diet.

Homozygous missense variant of PTH (c.166C>T, p.(Arg56Cys)) as the cause of familial isolated hypoparathyroidism in a three-year-old child

OBJECTIVES

Hypoparathyroidism is a rare disorder which is predominantly of idiopathic or genetic origin in children. The diagnosis is made from the biochemical measurement of parathyroid hormone (PTH), and the key findings include a low PTH in combination with hypocalcemia and hyperphosphatemia. However, the level of PTH encountered in patients with hypoparathyroidism may be dependent on the underlying genetic cause of the disorder as well as the biochemical assay used for assessment of PTH.

CASE PRESENTATION

A three-year-old child with asymptomatic primary hypoparathyroidism was identified with a homozygous missense variant of PTH. A sudden unexpected high PTH result after a shift from 2nd to 3rd generation PTH assay in the routine laboratory provided a clue on the underlying genetic etiology.

CONCLUSIONS

Pathogenic variants of PTH as a cause of hypoparathyroidism are rarely described. In this case, the child was asymptomatic, and discordant PTH results were seen with different assays.

Clinical and Molecular Diagnosis of Osteocraniostenosis in Fetuses and Newborns: Prenatal Ultrasound, Clinical, Radiological and Pathological Features

Osteocraniostenosis (OCS, OMIM #602361) is a severe, usually lethal condition characterized by gracile bones with thin diaphyses, a cloverleaf-shaped skull and splenic hypo/aplasia. The condition is caused by heterozygous mutations in the FAM111A gene and is allelic to the non-lethal, dominant disorder Kenny‐Caffey syndrome (KCS, OMIM #127000). Here we report two new cases of OCS, including one with a detailed pathological examination. We review the main diagnostic signs of OCS both before and after birth based on our observations and on the literature. We then review the current knowledge on the mutational spectrum of FAM111A associated with either OCS or KCS, including three novel variants, both from one of the OCS fetuses described here, and from further cases diagnosed at our centers. This report refines the previous knowledge on OCS and expands the mutational spectrum that results in either OCS or KCS.

Therapy with PTH 1-34 or calcitriol and calcium in diverse etiologies of hypoparathyroidism over 27 years at a single tertiary care center

OBJECTIVE

Hypoparathyroidism has heterogeneous genetic and acquired etiologies with a broad spectrum of severity. Herein we describe the clinical outcomes of the largest cohort of hypoparathyroid patients reported to date, who were followed over 27-years.

DESIGN

Pooled analysis of current and past studies describing the differential responses to PTH 1-34 injections vs conventional therapy among the varied hypoPT etiologies.

METHODS

192 participants (ages 2-74 years) with hypoparathyroidism who received either calcitriol and calcium or PTH 1-34 by subcutaneous injection.

RESULTS

Among the 4 main etiologic categories of hypoparathyroidism (autoimmune polyglandular failure type 1, activating mutation of the calcium receptor, surgical, and idiopathic hypoparathyroidism), we reveal significant differences in PTH 1-34 dose requirements, prevalence of nephrocalcinosis, biomarkers of mineral homeostasis, and pharmacodynamic profiles. Serum 1,25-dihydroxyvitamin D₃ increased significantly (P < 0.001) and 25-hydroxyvitamin D levels decreased during PTH 1-34 injections compared to calcitriol therapy (P < 0.01). Post-surgical patients achieved consistently lower urine calcium excretion over long-term PTH 1-34 therapy compared to conventional therapy (p < 0.001), but this was not achieved in the other etiologies. At study entry, patients had a high prevalence of renal insufficiency and nephrocalcinosis which were directly related to the duration of hypoparathyroidism (P < 0.03). Renal function remained stable during participation in our studies for both PTH 1-34 and conventional therapies.

CONCLUSIONS

We conclude that the effects and dose-response of PTH 1-34 treatment differ according to the etiology of hypoparathyroidism. Postsurgical hypoPT maintained mean serum calcium levels in the mid- to low-normal range while concurrently maintaining normal mean urine calcium during long-term twice-daily PTH 1-34 therapy.

Characterization of the clinical and genetic spectrum of autoimmune polyendocrine syndrome type 1 in Chinese case series

BACKGROUND

Autoimmune polyendocrine syndrome type 1 (APS1) is a hereditary disease caused by mutations in the AIRE gene with both endocrine and non-endocrine organ involvement. The existing data from China are limited, and this study aims to describe the phenotypes and genetic characterization in Chinese APS1 patients. In this single-center, retrospective, observational study, comprehensive endocrine and extra-endocrine manifestations were collected, and genetic analysis in AIRE was conducted in patients with APS1 between the years of 1984 and 2018 at Peking Union Medical College Hospital.

RESULTS

In total, 13 patients from 12 unrelated families were enrolled, seven of whom were female, with hypoparathyroidism, chronic mucocutaneous candidiasis, and Addison's disease being the most frequently observed manifestations. Up to 84.7% presented with two or three of the above-mentioned manifestations, and nearly 4.9 ± 1.8 components presented in patients aged 21.2 ± 7.9 years old. Several less common phenotypes, such as myeloproliferative disease, pure red cell aplasia, renal tubular acidosis, asplenia, autoimmune hepatitis, and ankylosing spondylitis, were also observed in patients. Altogether, seven different AIRE mutations were found in six patients, four of which (K161fs, G208V, A246fs, and L308F) had not been previously reported in patients with APS1.

CONCLUSION

We have provided a comprehensive profile of Chinese patients with APS1, with less commonly observed features being observed in addition to more regularly seen manifestations. Additionally, different AIRE mutations that were observed have expanded the genetic spectrum, which will help with future understanding of the molecular pathogenesis of APS1.

Genotype-phenotype spectrum in isolated and syndromic nanophthalmos

PURPOSE

To (i) describe a series of patients with isolated or syndromic nanophthalmos with the underlying genetic causes, including novel pathogenic variants and their functional characterization and (ii) to study the association of retinal dystrophy in patients with MFRP variants, based on a detailed literature review of genotype-phenotype correlations.

METHODS

Patients with nanophthalmos and available family members received a comprehensive ophthalmological examination. Genetic analysis was based on whole-exome sequencing and variant calling in core genes including MFRP, BEST1, TMEM98, PRSS56, CRB1, GJA1, C1QTNF5, MYRF and FAM111A. A minigene assay was performed for functional characterization of a splice site variant.

RESULTS

Seven patients, aged between three and 65 years, from five unrelated families were included. Novel pathogenic variants in MFRP (c.497C>T, c.899-3C>A, c.1180G>A), and PRSS56 (c.1202C>A), and a recurrent de novo variant in FAM111A (c.1706G>A) in a patient with Kenny-Caffey syndrome type 2, were identified. In addition, we report co-inheritance of MFRP-related nanophthalmos and ADAR-related Aicardi-Goutières syndrome.

CONCLUSION

Nanophthalmos is a genetically heterogeneous condition, and the severity of ocular manifestations appears not to correlate with variants in a specific gene. However, retinal dystrophy is only observed in patients harbouring pathogenic MFRP variants. Furthermore, heterozygous carriers of MFRP and PRSS56 should be screened for the presence of high hyperopia. Identifying nanophthalmos as an isolated condition or as part of a syndrome has implications for counselling and can accelerate the interdisciplinary care of patients.

Renal complications in patients with chronic hypoparathyroidism on conventional therapy: a systematic literature review : Renal disease in chronic hypoparathyroidism

A systematic literature review was performed to summarize the frequency and nature of renal complications in patients with chronic hypoparathyroidism managed with conventional therapy. Methodology was consistent with the recommendations outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Peer-reviewed journal articles with specified medical subject heading terms were identified using the PubMed, EMBASE, and Cochrane databases. Data were extracted from eligible articles based on prespecified parameters for clinical outcomes of renal calcifications and disease. Because of the heterogeneity of the data, a meta-analysis could not be conducted. From 1200 potentially relevant articles, data were extracted from 13 manuscripts that reported data for ≥1 of the 19 predefined renal outcomes for ≥10 adult patients (n = 11 manuscripts) or pediatric patients (n = 2 manuscripts). The collective data provide evidence that adult and pediatric patients with chronic hypoparathyroidism and treated with conventional therapy (oral calcium and active vitamin D) had an increased risk of renal complications. The reported rate of nephrolithiasis was up to 36%, with the lowest rates in studies reporting shorter duration of disease. The rate of nephrocalcinosis was up to 38%. Some studies reported a combined nephrolithiasis/nephrocalcinosis outcome of 19% to 31%. Data for renal disease that encompassed a range of renal insufficiency to chronic kidney disease were reported in 10 articles; the reported rates ranged from 2.5% to 41%. In patients who receive long-term treatment with oral calcium and active vitamin D, chronic hypoparathyroidism may be associated with an increased risk of renal complications compared with the general population.

Adult Chinese twins with Kenny-Caffey syndrome type 2: A potential age-dependent phenotype and review of literature

Kenny-Caffey syndrome (KCS) type 2 (OMIM 127000) is a rare syndromic cause of hypoparathyroidism which is characterized by proportionate short stature, long bone abnormalities, delayed closure of anterior fontanelle, eye abnormalities, and normal intelligence. It is caused by variants in FAM111A (NM_001942519.1). In this review, we reported the first Chinese patients, a pair of monozygotic twins, with genetically confirmed KCS type 2 with over 20 years follow-up. We summarized the clinical features of 14 previously reported and genetically confirmed KCS type 2 patients; our twin patients exhibited a unique spinal manifestation which could be an important age-dependent feature of KCS type 2. In this review, over 60% KCS type 2 patients had dental problem and over 80% suffered from refractive errors or structural eye abnormalities. Therefore, early dental, ophthalmological, and orthopedic assessments are warranted for KCS type 2 patients. Micro-orchidism, previously reported in KCS type 2 patients, was also detected in our patients. The possibility of subfertility should be considered in male KCS type 2 patients. A multidisciplinary management approach for this rare syndrome is recommended.

Hypoparathyroidism, deafness, and renal dysplasia syndrome: 20 Years after the identification of the first GATA3 mutations

The hypoparathyroidism, deafness, and renal dysplasia (HDR) syndrome is an autosomal dominant disorder caused by heterozygous mutations of the GATA3 gene. In the last 20 years, since the identification of the genetic cause of the HDR syndrome, GATA3 mutations have been reported in 124 families (177 patients). The clinical aspects and molecular genetics of the HDR syndrome are reviewed here together with the reported mutations and phenotypes. Reported mutations consist of 40% frameshift deletions or insertions, 23% missense mutations, 14% nonsense mutations, 6% splice-site mutations, 1% in-frame deletions or insertions, 15% whole-gene deletions, and 1% whole-gene duplication. Missense mutations were found to cluster in the regions encoding the two GATA3 zinc-finger domains. Patients showed great clinical variability and the penetrance of each HDR defect increased with age. The most frequently observed abnormality was deafness (93%), followed by hypoparathyroidism (87%) and renal defects (61%). The mean age of diagnosis of HDR was 15.3, 7.5, and 14.0 years, respectively. However, patients with whole-gene deletions and protein-truncating mutations were diagnosed earlier than patients with missense mutations.

Hypoparathyroidism

BACKGROUND

Hypoparathyroidism is a rare endocrine disorder characterized by hypocalcemia and low or undetectable levels of parathyroid hormone.

METHODS

This review is an evidence-based summary of hypoparathyroidism in terms of relevant pathophysiological, clinical, and therapeutic concepts.

RESULTS

Many clinical manifestations of hypoparathyroidism are due to the lack of the physiological actions of parathyroid hormone on its 2 major target organs: the skeleton and the kidney. The skeleton is inactive, accruing bone without remodeling it. The kidneys lose the calcium-conserving actions of parathyroid hormone and, thus, excrete a greater fraction of calcium. Biochemical manifestations, besides hypocalcemia and low or undetectable levels of parathyroid hormone, include hyperphosphatemia and low levels of 1,25-dihydroxyvitamin D. Calcifications in the kidney, brain, and other soft tissues are common. Removal of, or damage to, the parathyroid glands at the time of anterior neck surgery is, by far, the most likely etiology. Autoimmune destruction of the parathyroid glands and other genetic causes represent most of the other etiologies. Conventional treatment with calcium and active vitamin D can maintain the serum calcium level but high doses may be required, adding to the risk of long-term soft tissue calcifications. The advent of replacement therapy with recombinant human PTH(1-84) represents a major step in the therapeutics of this disease.

CONCLUSIONS

Advances in our knowledge of hypoparathyroidism have led to greater understanding of the disease itself and our approach to it.

Novel heterozygous GATA3 and SLC34A3 variants in a 6-year-old boy with Barakat syndrome and hypercalciuria

BACKGROUND

Barakat syndrome is an autosomal dominant disorder characterized by the triad of hypoparathyroidism, sensorineural deafness, and renal anomalies and is caused by mutations in GATA3 gene. SLC34A3 is the cause gene of hypophosphatemic rickets with hypercalciuria, and heterozygous carriers may have milder clinical symptoms. The aim of this study was to identify the underlying genetic cause of a patient who initially presented with renal failure, hypercalciuria, kidney stone, and bilateral sensorineural deafness.

METHODS

A 6-year-old boy with complex clinical presentations was investigated. Comprehensive medical evaluations were performed including auditory function tests, endocrine function tests, metabolic studies, and imaging examinations. Molecular diagnoses were analyzed by trio whole-exome sequencing.

RESULTS

One novel de novo deleterious variant (c. 324del) of the GATA3 gene was identified in the patient. The patient can be diagnosed with Barakat syndrome. In addition, one novel variant (c. 589A>G) of the SLC34A3 gene was detected, which was inherited from the father. This heterozygous variant can explain the hypercalciuria and kidney stone that occurred in both the patient and his father.

CONCLUSION

This study provides a special case which is phenotype-driven dual diagnoses, and the two novel variants can parsimoniously explain the complex clinical presentations of this patient.

A case report and literature review: Identification of a novel AIRE gene mutation associated with Autoimmune Polyendocrine Syndrome Type 1 in East Asians

RATIONALE

Autoimmune polyendocrine syndrome type 1 (APS-1), also referred as the autoimmune polyendocrinopathy candidiasis-ectodermal dystrophy (APECED), is a rare autosomal inherited disease predominantly among Caucasians from Northern Europe. This syndrome is very rare in East Asian population.

PATIENTS CONCERNS

Here, we describe a case of a 15-year-old Chinese boy admitted due to a 1-month history of intermittent fatigue, nausea, vomiting, and diarrhea. His symptom became worse accompanied with chest tightness 4 days before admission. On physical examination, his temperature was 38.5°C, blood pressure was 75/38 mm Hg, and pulse was 98/min. He was a thin boy with mild hyperpigmentation and xanthochromia.

DIAGNOSIS

After abdominal computed technology and laboratory tests, his diagnosis was APS-1 accompanied with adrenal crisis. Further investigation on whole-exome sequencing revealed a novel homozygous mutation c.47C>G (p.T16R) in exon 1 in the autoimmune regulator (AIRE) gene.

INTERVENTIONS

This patient underwent replacement therapy of glucocorticoids, corticosteroid, and levothyroxine, as well as calcium and calcitriol supplementation.

OUTCOMES

He continues to do well 4 years after his hospitalization. During his last follow-up, he had serum thyroid-stimulating hormone level of 3.07 μIU/mL, free triiodothyronine level of 1.92 pg/mL, and free thyroxine level of 13.95 pg/mL. His serum cortisol and ACTH (8 a.m.) levels were 28.53 μg/dL and 69.48 pg/mL, respectively.

LESSONS

APS-1 is very rare in East Asians and the variable clinical presentations of the disease make the initial diagnosis especially difficult. Autoimmune thyroiditis, type 1 diabetes mellitus, and hepatitis were the three most frequent minor components of APS-1 in East Asian patients with age of onset in late teens and 20s. Sequence analysis of AIRE gene is necessary to verify its diagnostic efficacy in association with clinical findings.

Genetic Screening in a Large Chinese Cohort of Childhood Onset Hypoparathyroidism by Next-Generation Sequencing Combined with TBX1-MLPA

At least 15 candidate genes have been implicated in hypoparathyroidism (HP). However, comprehensive screening of causative genes for HP is lacking. Here, we investigated the genotype spectrum in a large group of Chinese patients with childhood onset HP. A total of 173 patients with childhood onset HP were analyzed using targeted next-generation sequencing (NGS), including 15 candidate genes combined with multiplex ligation-dependent probe amplification (MLPA) of the TBX1 gene. Twenty-seven pathogenic or likely pathogenic mutations in five genes (TBX1, AIRE, GATA3, FAM111A, and CASR) including 13 novel variants in 23 patients, and 12 variants of uncertain clinical significance in five genes (GATA3, CASR, FAM111A, GCM2, and PTH) in 11 patients, were identified by NGS. Additionally, an entire gene deletion of TBX1 in 25 patients was found by TBX1-MLPA. Combined with clinical data, 26 (15.0%) cases of DiGeorge syndrome (OMIM #188400), nine (5.2%) autoimmune polyglandular syndrome type 1 (OMIM #240300), eight (4.6%) autosomal dominant hypocalcemia type 1 (OMIM #601198), four (2.3%) hypoparathyroidism-deafness-renal dysplasia syndrome (OMIM #146255), and one (0.6%) Kenny-Caffey syndrome type 2 (OMIM #127000) were verified. Among them, 16 of 26 (61.5%) DiGeorge syndrome cases were undiagnosed due to the lack of obvious clinical clues before genetic testing. The onset age of patients with mutations (median [interquartile range], 2.8 [0.1, 9.6] years) was significantly earlier than those without mutations (13.0 [8.8, 15.0] years) (p < 0.001). Family history, early onset age, especially prior to 5 years old, and extraparathyroid manifestations were clues for hereditary HP. The combined targeted NGS and TBX-1 MLPA were conveniently and effectively used for comprehensive genetic screening in this large Chinese cohort of childhood onset HP patients. Genetic defects were identified in 27.7% of early-onset HP patients, including four kinds of syndromic HP and one isolated HP. A total of 13 novel mutations were detected, which expands the mutation spectrum of hypoparathyroidism. © 2019 American Society for Bone and Mineral Research.

Causes and pathophysiology of hypoparathyroidism

Hypoparathyroidism, a disorder characterized by hypocalcemia ensuing from inadequate parathyroid hormone secretion, is a rather rare disorder caused by multiple etiologies. When not caused by inadvertent damage or removal of the parathyroids during neck surgery, it is usually genetically determined. Epidemiological figures of this disease are still scarce and mainly limited to countries where non-anonymous databases are available and to surgical case series. Both the surgical and non-surgical forms pose diagnostic challenges. For surgical hypoparathyroidism, transient forms have to be ruled out even in the long term, in order to avoid unnecessary chronic replacement therapy with calcium and calcitriol. Regarding non-surgical hypoparathyroidism, once referred to as idiopathic, a systematic clinically and genetically-driven approach to define the precise diagnosis have to be pursued. In the case of syndromic hypoparathyroidism, patients have to be screened for associated abnormalities. Autoimmune, non-genetic hypoparathyroidism is still a diagnosis of exclusion, since no specific autoantibodies are specific for this condition.

A case of severe TBCE-negative hypoparathyroidism-retardation-dysmorphism syndrome: Case report and literature review

Hypoparathyroidism-retardation-dysmorphism syndrome (HRD) is a rare autosomal recessive disorder attributed to the mutations in the tubulin-specific chaperone E (TBCE) gene, which is vital for microtubule function during mitosis, organelle positioning, and neuronal cytokinesis. HRD is a congenital syndromic hypoparathyroidism associated with growth deficiency, microcephaly, intellectual disability, ocular anomalies, and facial dysmorphism. To our knowledge, there is only one published case of mild HRD-like syndrome with no identifiable genetic etiology. We report a case of severe TBCE-negative phenotypic HRD in a 4-year-old female from India presenting with hypocalcemic seizures due to congenital hypoparathyroidism, extreme microcephaly, growth deficiency, ocular anomalies, and facial dysmorphism. SNP microarray and whole exome sequencing (WES) did not detect any abnormalities in TBCE or other genes of interest. WES revealed two variants of unknown clinical significance in CASC5 gene, which codes for a protein in the kinetochore and, interestingly similar to TBCE, is essential for proper microtubule function during mitosis and cell proliferation and has been implicated in primary microcephaly disorders. However, further targeted sequencing in the parents revealed both variants inherited from the unaffected mother. Significant copy number variant noise in the proband and her parents limited further analysis. At this time the role of variants in the CASC5 gene is unclear and cannot explain our patient's phenotype. In conclusion, we report a severe case of phenotypic HRD syndrome, in which extensive genetic evaluation failed to reveal an etiology. Our case demonstrates that the pathogenesis of HRD may be genetically heterogenous, meriting further genetic investigations.

Hypoparathyroidism

Hypoparathyroidism is a disease characterized by inadequately low circulating concentrations of parathyroid hormone (PTH) resulting in low calcium levels and increased phosphate levels in the blood. Symptoms of the disease result from increased neuromuscular irritability caused by hypocalcaemia and include tingling, muscle cramps and seizures. The most common cause of the disease is inadvertent removal of, or injury to, the parathyroid glands during neck surgery, followed by genetic, idiopathic and autoimmune aetiologies. Conventional treatment includes activated vitamin D and/or calcium supplements, but this treatment does not fully replace the functions of PTH and can lead to short-term problems (such as hypocalcaemia, hypercalcaemia and increased urinary calcium excretion) and long-term complications (which include nephrocalcinosis, kidney stones and brain calcifications). PTH replacement has emerged as a new treatment option. Clinical trials using human PTH(1-34) and PTH(1-84) showed that this treatment was safe and effective in studies lasting up to 6 years. Recombinant human PTH(1-84) has been approved in the United States and Europe for the management of hypoparathyroidism; however, its effect on long-term complications is still being evaluated. Clinical practice guidelines, which describe the consensus of experts in the field, have been published and recognize the need for more research to optimize care. In this Primer, we summarize current knowledge of the prevalence, pathophysiology, clinical presentation and management of hypoparathyroidism.

Short stature and hypoparathyroidism in a child with Kenny-Caffey syndrome type 2 due to a novel mutation in FAM111A gene

Background

Hypoparathyroidism in children is a heterogeneous group with diverse genetic etiologies. To aid clinicians in the investigation and management of children with hypoparathyroidism, we describe the phenotype of a 6-year-old child with hypoparathyroidism and short stature diagnosed with Kenny-Caffey syndrome (KCS) Type 2 and the subsequent response to growth hormone (GH) treatment.

Case presentation

The proband presented in the neonatal period with hypocalcemic seizures secondary to hypoparathyroidism. Her phenotype included small hands and feet, hypoplastic and dystrophic nails, hypoplastic mid-face and macrocrania. Postnatal growth was delayed but neurodevelopment was normal. A skeletal survey at 2 years of age was suggestive of KCS Type 2 and genetic testing revealed a novel de novo heterozygous mutation c.1622C > A (p.Ser541Tyr) in FAM111A. At 3 years and 2 months, her height was 80cms (SDS −3.86). She had normal overnight GH levels. GH therapy was commenced at a dose of 4.9 mg/m²/week for her short stature and low height velocity of 5cms/year. At the end of the first and second years of GH treatment, height velocity was 6.5cms/year and 7.2cms/year, respectively with maximal dose of 7.24 mg/m²/week.

Conclusion

This case highlights the phenotype and the limited response to GH in a child with genetically proven KCS type 2. Long-term registries monitoring growth outcomes following GH therapy in patients with rare genetic conditions may help guide clinical decisions regarding the use and doses of GH in these conditions.