Hypophosphatasia

2021 ◽  
pp. jclinpath-2021-207426
Author(s):  
Jonathan Samuel Fenn ◽  
Nathan Lorde ◽  
John Martin Ward ◽  
Ingrid Borovickova
Keyword(s):  
Serum Alkaline Phosphatase ◽  
Incidental Finding ◽  
Correct Diagnosis ◽  
Loss Of Function ◽  
Inherited Disorders ◽  
Gene Encoding ◽  
Genetic Characteristics ◽  
Enzyme Replacement ◽  
Alp Activity ◽  
Low Serum

Hypophosphatasia (HPP) is a group of inherited disorders characterised by the impaired mineralisation of bones and/or teeth and low serum alkaline phosphatase (ALP) activity. It is caused by a mutation in the ALPL gene encoding the tissue-non-specific isoenzyme of ALP (TNSALP) resulting in a loss of function. The disease is highly heterogenous in its clinical expression ranging from stillbirth without mineralised bone to the mild form of late adult onset with symptoms and signs such as musculoskeletal pain, arthropathy, lower-extremity fractures, premature loss of teeth or an incidental finding of reduced serum ALP activity. A classification based on the age at diagnosis and the presence or absence of bone symptoms was historically used: perinatal, prenatal benign, infantile, childhood, adult and odontohypophosphatasia. These subtypes are known to have overlapping signs and complications. Three forms of HPP distinguishable by their genetic characteristics have been described: severe, moderate and mild. Severe forms of HPP (perinatal and infantile severe) are recessively inherited, whereas moderate HPP may be dominantly or recessively inherited. The biochemical hallmark of HPP is persistently low serum ALP for age and increase in natural substrates of TNSALP, pyridoxal 5′-phosphate and phosphoethanolamine supported by radiological findings. The diagnosis is confirmed by ALPL sequencing. A multidisciplinary team of experts is essential for the effective management. Calcium restriction is recommended in infants/children to manage hypercalcaemia. A targeted enzyme replacement therapy for HPP has become available and correct diagnosis is crucial to allow early treatment.

scholarly journals SUN-LB64 Urine Phosphoethanolamine Is an Underutilized Biomarker for Hypophosphastasia

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Zahra Shajani-Yi ◽  
Nadia Ayala-Lopex ◽  
Margo Black ◽  
Kathryn McCrystal Dahir
Keyword(s):  
Functional Performance ◽  
Clinical Phenotype ◽  
Surrogate Marker ◽  
Reference Interval ◽  
Joint Disease ◽  
Activity Levels ◽  
Loss Of Function ◽  
Inorganic Pyrophosphate ◽  
Enzyme Replacement ◽  
Alp Activity

Abstract Hypophosphatasia (HPP) is a rare disease caused by a loss-of-function mutation in the ALPL gene leading to a deficiency in the tissue-non-specific isoenzyme alkaline phosphatase (ALP) and excess of extracellular inorganic pyrophosphate (PPi) and pyridoxal 5’phosphate (PLP). Patients with HPP have a widely variable clinical phenotype, from neonatal seizures and hypomineralization to isolated dental or joint disease in adults. Patients present with ALP activity levels below their age-adjusted reference interval and elevations in PLP. This variable clinical phenotype leads to significant diagnostic challenges, particularly in those with minor disease manifestations. Biomarkers for diagnosing HPP and monitoring patients on enzyme replacement therapy (ERT) are limited. Low ALP activity is not specific for HPP; it can be low in other conditions including untreated hypothyroidism, and other skeletal dysplasias. Accurate PLP assessment is limited in patients on ERT due to hydrolysis of the substrate. Phosphoethanolamine (PEA) is a substrate hydrolyzed by TNSALP and elevated levels of PEA may be observed in HPP, supporting the diagnosis of HPP, but have been reported to be non-specific. We hypothesized that urine PEA levels could be used to diagnose HPP and as a surrogate marker for ERT compliance. We performed a retrospective analysis on 83 adult patients (63F: 20M) presenting for investigation or follow-up of HPP from 7/1/2014 to 1/7/2020. Urine was sent to the Children’s Hospital in Colorado for PEA testing. Patients were diagnosed with HPP if they had ALP levels persistently below the age-adjusted reference interval, were positive for an ALPL gene mutation/had a family history of HPP and had musculoskeletal/dental symptoms consistent with the disease. Patients were negative for HPP if ALP was not persistently low, vitamin B6 levels were normal without supplementation, negative ALPL genetic testing results (when available) and no musculoskeletal/dental symptoms. PEA levels were not considered for diagnosis. The following was collected from the EMR: PEA results, diagnosis, and ERT status. PEA levels were higher in patients with HPP not on ERT (median=117.0, N=39) vs. those negative for HPP (median=24.0, N=15, p<0.0001). The receiver operator curve for PEA in diagnosing HPP had an AUC of 0.94 (SE=0.03, p<0.0001). Specificity was 100% at PEA levels >53.5 ng/ml (sensitivity=79.5%) with an NPV of 65.2% and PPV of 100%. Initial PEA values in patients with HPP and not on ERT were higher (median 117.0, N=39) than patients on ERT (median 65.0, N=16, p=0.004). Patients who began ERT had a decline in PEA levels after treatment (mean decrease 68.1%). PEA is a specific diagnostic marker for HPP in patients undergoing investigation for HPP and may be used as a surrogate marker to monitor ERT compliance. Future studies are necessary to evaluate the association between PEA levels and functional performance.

scholarly journals Hypophosphatasia

2021 ◽  
Vol 10 (23) ◽  
pp. 5676
Author(s):  
Symeon Tournis ◽  
Maria P. Yavropoulou ◽  
Stergios A. Polyzos ◽  
Artemis Doulgeraki
Keyword(s):  
Alkaline Phosphatase ◽  
Autosomal Dominant ◽  
Serum Alkaline Phosphatase ◽  
Severe Disease ◽  
Loss Of Function ◽  
Inorganic Pyrophosphate ◽  
Live Births ◽  
Enzyme Replacement ◽  
Asfotase Alfa ◽  
Reduced Activity

Hypophosphatasia (HPP) is an inherited metabolic disease caused by loss-of-function mutations in the tissue non-specific alkaline phosphatase (TNAP) gene. Reduced activity of TNAP leads to the accumulation of its substrates, mainly inorganic pyrophosphate and pyridoxal-5΄-phosphate, metabolic aberrations that largely explain the musculoskeletal and systemic features of the disease. More than 400 ALPL mutations, mostly missense, are reported to date, transmitted by either autosomal dominant or recessive mode. Severe disease is rare, with incidence ranging from 1:100,000 to 1:300,000 live births, while the estimated prevalence of the less severe adult form is estimated to be between 1:3100 to 1:508, in different countries in Europe. Presentation largely varies, ranging from death in utero to asymptomatic adults. In infants and children, clinical features include skeletal, respiratory and neurologic complications, while recurrent, poorly healing fractures, muscle weakness and arthropathy are common in adults. Persistently low serum alkaline phosphatase is the cardinal biochemical feature of the disease. Management requires a dedicated multidisciplinary team. In mild cases, treatment is usually symptomatic. Severe cases, with life-threating or debilitating complications, can be successfully treated with enzyme replacement therapy with asfotase alfa.

scholarly journals MON-361 Late Diagnosis in Adult Form of Hypophosphatasia

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Marina Sousa da Silva ◽  
Joao Lindolfo Borges
Keyword(s):  
Alkaline Phosphatase ◽  
Serum Alkaline Phosphatase ◽  
Correct Diagnosis ◽  
Pathologic Fracture ◽  
Stress Fractures ◽  
Thigh Pain ◽  
Mineral Density ◽  
Adult Form ◽  
The Right ◽  
Low Serum

Abstract INTRODUCTION/BACKGROUND: Hypophosphatasia is a rare inborn error of metabolism that presents with important foot and thigh pain due to stress fractures. The diagnose of the adult form is routinely neglected, even though it presents symptomatic and with persistent low serum alkaline phosphatase (ALP). CLINICAL CASE (DIAGNOSTIC EVALUATION, TRATMANET AND FUP): A 43-year-old amateur athlete woman presented with pain in the right femur without any local trauma. Physical examination evidenced prolonged right tight pain and no other findings. Bone mineral density evaluated by dual-energy x-ray absorptiometry was unremarkable. Biochemical investigations showed normal inorganic phosphate, calcium, zinc, and magnesium, but low ALP. The patient had six previous ALP measurements and all of them were below the lower limit of normality (46 a 116 U/L). These measurements were done in regular ob-gyn checkups with no further investigation or follow-up. In light of the hypophosphatasemia and pathologic fracture, the serum pyridoxal 5’-phosphate concentration was measured and found to be elevated 35,8 mcg/L (normal 5,0 a 30,0 mcg/L). CLINICAL LESSONS/CONCLUSION: Hypophosphatasia occurs due to a deactivating mutation (or mutations) of the gene encoding Tissue-Nonspecific Alkaline Phosphatase (TNSALP), leading to a global deficiency of TNSALP activity and inadequate skeletal mineralization and fractures. The adult form presents during middle age with stress fractures. The first complaints maybe foot pain, which is due to stress fractures of the metatarsals, and thigh pain, due to pseudo fractures of the femur. Our patient illustrates the importance of low serum ALP activity in the assessment of these patients. The correct diagnosis should help to avoid the use of traditional therapies for osteoporosis or osteomalacia, which would be ineffective or potentially harmful.

Significance of low serum alkaline phosphatase activity in a predominantly adult male population

1995 ◽  
Vol 41 (4) ◽  
pp. 515-518 ◽  
Author(s):  
G Lum
Keyword(s):  
Alkaline Phosphatase ◽  
Cardiac Surgery ◽  
Adult Male ◽  
Magnesium Deficiency ◽  
Serum Alkaline Phosphatase ◽  
Medical Center ◽  
Male Population ◽  
Serum Alkaline Phosphatase Activity ◽  
Alp Activity ◽  
Low Serum

Abstract The causes for low serum alkaline phosphatase (ALP) activity (reference range 30-115 U/L) in a large Veterans Medical Center were reviewed. Of 69,864 ALP determinations made over a 4-year period, 130 were low (< 30 U/L, 0.19%), representing 88 individual patients. Of these, 83 (primarily men, 96%) patients' charts were reviewed and classified into two groups, those with and those without conditions previously reported to be associated with decreased serum ALP activity: 47% had conditions associated with low ALP activity, the most frequent being cardiac surgery and cardiopulmonary bypass (26.5%), malnutrition (12.0%), magnesium deficiency (4.8%), hypothyroidism (2.4%), and severe anemia (1.2%); 53% of patients did not have clinical conditions previously associated with low ALP activity. No case of clinically apparent hypophosphatasia, for which low ALP activity is the defining characteristic, was found in this population of veterans. A low serum ALP may be of significance in other patient populations such as children, where it is associated with achondroplasia and cretinism, or in postmenopausal women with osteoporosis taking estrogen replacement therapy. In the predominantly adult male population in this study, low ALP activity was rare; it was seen most frequently in cardiac surgery patients postoperatively, a clinical condition heretofore not commonly associated with low serum ALP activity.

scholarly journals TorsinB overexpression prevents abnormal twisting in DYT1 dystonia mouse models

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Jay Li ◽  
Chun-Chi Liang ◽  
Samuel S Pappas ◽  
William T Dauer
Keyword(s):  
Mouse Models ◽  
Symptom Development ◽  
Loss Of Function ◽  
Genetic Redundancy ◽  
Inherited Disorders ◽  
Gene Encoding ◽  
Dyt1 Dystonia ◽  
Abnormal Movements ◽  
Membrane Budding ◽  
Dose Dependent

Genetic redundancy can be exploited to identify therapeutic targets for inherited disorders. We explored this possibility in DYT1 dystonia, a neurodevelopmental movement disorder caused by a loss-of-function (LOF) mutation in the TOR1A gene encoding torsinA. Prior work demonstrates that torsinA and its paralog torsinB have conserved functions at the nuclear envelope. This work established that low neuronal levels of torsinB dictate the neuronal selective phenotype of nuclear membrane budding. Here, we examined whether torsinB expression levels impact the onset or severity of abnormal movements or neuropathological features in DYT1 mouse models. We demonstrate that torsinB levels bidirectionally regulate these phenotypes. Reducing torsinB levels causes a dose-dependent worsening whereas torsinB overexpression rescues torsinA LOF-mediated abnormal movements and neurodegeneration. These findings identify torsinB as a potent modifier of torsinA LOF phenotypes and suggest that augmentation of torsinB expression may retard or prevent symptom development in DYT1 dystonia.

scholarly journals TorsinB overexpression prevents abnormal twisting in DYT1 dystonia mouse models

2019 ◽  
Author(s):  
Jay Li ◽  
Chun-Chi Liang ◽  
Samuel S. Pappas ◽  
William T. Dauer
Keyword(s):  
Mouse Models ◽  
Prior Work ◽  
Symptom Development ◽  
Loss Of Function ◽  
Genetic Redundancy ◽  
Inherited Disorders ◽  
Gene Encoding ◽  
Dyt1 Dystonia ◽  
Abnormal Movements ◽  
Membrane Budding

AbstractGenetic redundancy can be exploited to identify therapeutic targets for inherited disorders. An example is DYT1 dystonia, a neurodevelopmental movement disorder caused by a loss-of-function (LOF) mutation in the TOR1A gene encoding torsinA. Prior work demonstrates that torsinA and its paralog torsinB have conserved functions at the nuclear envelope. This work established that low neuronal levels of torsinB dictate the neuronal selective phenotype of nuclear membrane budding. Here, we examined whether torsinB expression levels impact the onset or severity of abnormal movements, or neuropathological features in DYT1 mouse models. We demonstrate that torsinB levels bidirectionally regulate these phenotypes. Reducing torsinB levels causes a dosedependent worsening whereas torsinB overexpression rescues torsinA LOF-mediated abnormal movements and neurodegeneration. These findings identify torsinB as a potent modifier of torsinA LOF phenotypes and suggest that augmentation of torsinB expression level may retard or prevent symptom development in DYT1 dystonia.

scholarly journals Gain-of-function GABRB3 variants identified in vigabatrin-hypersensitive epileptic encephalopathies

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Nathan L Absalom ◽  
Vivian W Y Liao ◽  
Kavitha Kothur ◽  
Dinesh C Indurthi ◽  
Bruce Bennetts ◽  
...  
Keyword(s):  
De Novo ◽  
Drug Effects ◽  
Receptor Expression ◽  
Aminobutyric Acid ◽  
Loss Of Function ◽  
Molecular Phenotype ◽  
Gain Of Function ◽  
Gene Encoding ◽  
Epileptic Encephalopathies ◽  
Receptor Phenotype

Abstract Variants in the GABRB3 gene encoding the β3-subunit of the γ-aminobutyric acid type A ( receptor are associated with various developmental and epileptic encephalopathies. Typically, these variants cause a loss-of-function molecular phenotype whereby γ-aminobutyric acid has reduced inhibitory effectiveness leading to seizures. Drugs that potentiate inhibitory GABAergic activity, such as nitrazepam, phenobarbital or vigabatrin, are expected to compensate for this and thereby reduce seizure frequency. However, vigabatrin, a drug that inhibits γ-aminobutyric acid transaminase to increase tonic γ-aminobutyric acid currents, has mixed success in treating seizures in patients with GABRB3 variants: some patients experience seizure cessation, but there is hypersensitivity in some patients associated with hypotonia, sedation and respiratory suppression. A GABRB3 variant that responds well to vigabatrin involves a truncation variant (p.Arg194*) resulting in a clear loss-of-function. We hypothesized that patients with a hypersensitive response to vigabatrin may exhibit a different γ-aminobutyric acid A receptor phenotype. To test this hypothesis, we evaluated the phenotype of de novo variants in GABRB3 (p.Glu77Lys and p.Thr287Ile) associated with patients who are clinically hypersensitive to vigabatrin. We introduced the GABRB3 p.Glu77Lys and p.Thr287Ile variants into a concatenated synaptic and extrasynaptic γ-aminobutyric acid A receptor construct, to resemble the γ-aminobutyric acid A receptor expression by a patient heterozygous for the GABRB3 variant. The mRNA of these constructs was injected into Xenopus oocytes and activation properties of each receptor measured by two-electrode voltage clamp electrophysiology. Results showed an atypical gain-of-function molecular phenotype in the GABRB3 p.Glu77Lys and p.Thr287Ile variants characterized by increased potency of γ-aminobutyric acid A without change to the estimated maximum open channel probability, deactivation kinetics or absolute currents. Modelling of the activation properties of the receptors indicated that either variant caused increased chloride flux in response to low concentrations of γ-aminobutyric acid that mediate tonic currents. We therefore propose that the hypersensitivity reaction to vigabatrin is a result of GABRB3 variants that exacerbate GABAergic tonic currents and caution is required when prescribing vigabatrin. In contrast, drug strategies increasing tonic currents in loss-of-function variants are likely to be a safe and effective therapy. This study demonstrates that functional genomics can explain beneficial and adverse anti-epileptic drug effects, and propose that vigabatrin should be considered in patients with clear loss-of-function GABRB3 variants.

scholarly journals The Multifaceted Roles of MicroRNAs in Cystic Fibrosis

Diagnostics ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1102
Author(s):  
Fatima Domenica Elisa De Palma ◽  
Valeria Raia ◽  
Guido Kroemer ◽  
Maria Chiara Maiuri
Keyword(s):  
Cystic Fibrosis ◽  
Respiratory Infections ◽  
Current Knowledge ◽  
Pancreatic Insufficiency ◽  
Clinical Manifestations ◽  
Predictive Biomarkers ◽  
Loss Of Function ◽  
Gene Encoding ◽  
Multisystemic Disease

Cystic fibrosis (CF) is a lifelong disorder affecting 1 in 3500 live births worldwide. It is a monogenetic autosomal recessive disease caused by loss-of-function mutations in the gene encoding the chloride channel cystic fibrosis transmembrane conductance regulator (CFTR), the impairment of which leads to ionic disequilibria in exocrine organs. This translates into a chronic multisystemic disease characterized by airway obstruction, respiratory infections, and pancreatic insufficiency as well as hepatobiliary and gastrointestinal dysfunction. Molecular characterization of the mutational heterogeneity of CFTR (affected by more than 2000 variants) improved the understanding and management of CF. However, these CFTR variants are linked to different clinical manifestations and phenotypes, and they affect response to treatments. Expanding evidence suggests that multisystemic disease affects CF pathology via impairing either CFTR or proteins regulated by CFTR. Thus, altering the expression of miRNAs in vivo could constitute an appealing strategy for developing new CF therapies. In this review, we will first describe the pathophysiology and clinical management of CF. Then, we will summarize the current knowledge on altered miRNAs in CF patients, with a focus on the miRNAs involved in the deregulation of CFTR and in the modulation of inflammation. We will highlight recent findings on the potential utility of measuring circulating miRNAs in CF as diagnostic, prognostic, and predictive biomarkers. Finally, we will provide an overview on potential miRNA-based therapeutic approaches.

scholarly journals Genomic Variation in IbA10G2 and Other Patient-Derived Cryptosporidium hominis Subtypes

2016 ◽  
Vol 55 (3) ◽  
pp. 844-858 ◽  
Author(s):  
Per Sikora ◽  
Sofia Andersson ◽  
Jadwiga Winiecka-Krusnell ◽  
Björn Hallström ◽  
Cecilia Alsmark ◽  
...  
Keyword(s):  
Parasite Burden ◽  
Genomic Variation ◽  
Loss Of Function ◽  
Oocyst Wall ◽  
Gene Encoding ◽  
Cryptosporidium Hominis ◽  
Content Type ◽  
Successful Isolation ◽  
Target Dna ◽  
Stool Samples

ABSTRACTIn order to improve genotyping and epidemiological analysis ofCryptosporidiumspp., genomic data need to be generated directly from a broad range of clinical specimens. Utilizing a robust method that we developed for the purification and generation of amplified target DNA, we present its application for the successful isolation and whole-genome sequencing of 14 differentCryptosporidium hominispatient specimens. Six isolates of subtype IbA10G2 were analyzed together with a single representative each of 8 other subtypes: IaA20R3, IaA23R3, IbA9G3, IbA13G3, IdA14, IeA11G3T3, IfA12G1, and IkA18G1. Parasite burden was measured over a range of more than 2 orders of magnitude for all samples, while the genomes were sequenced to mean depths of between 17× and 490× coverage. Sequence homology-based functional annotation identified several genes of interest, including the gene encodingCryptosporidiumoocyst wall protein 9 (COWP9), which presented a predicted loss-of-function mutation in all the sequence subtypes, except for that seen with IbA10G2, which has a sequence identical to theCryptosporidium parvumreference Iowa II sequence. Furthermore, phylogenetic analysis showed that all the IbA10G2 genomes form a monophyletic clade in theC. hoministree as expected and yet display some heterogeneity within the IbA10G2 subtype. The current report validates the aforementioned method for isolating and sequencingCryptosporidiumdirectly from clinical stool samples. In addition, the analysis demonstrates the potential in mining data generated from sequencing multiple whole genomes ofCryptosporidiumfrom human fecal samples, while alluding to the potential for a higher degree of genotyping withinCryptosporidiumepidemiology.

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