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Stroup BM, Li X, Ho S, Zhouyao H, Chen Y, Ani S, Dawson B, Jin Z, Marom R, Jiang MM, Lorenzo I, Rosen D, Lanza D, Aceves N, Koh S, Seavitt JR, Heaney JD, Lee B, Burrage LC. Delayed skeletal development and IGF-1 deficiency in a mouse model of lysinuric protein intolerance. Dis Model Mech 2023; 16:dmm050118. [PMID: 37486182 PMCID: PMC10445726 DOI: 10.1242/dmm.050118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 07/14/2023] [Indexed: 07/25/2023] Open
Abstract
SLC7A7 deficiency, or lysinuric protein intolerance (LPI), causes loss of function of the y+LAT1 transporter critical for efflux of arginine, lysine and ornithine in certain cells. LPI is characterized by urea cycle dysfunction, renal disease, immune dysregulation, growth failure, delayed bone age and osteoporosis. We previously reported that Slc7a7 knockout mice (C57BL/6×129/SvEv F2) recapitulate LPI phenotypes, including growth failure. Our main objective in this study was to characterize the skeletal phenotype in these mice. Compared to wild-type littermates, juvenile Slc7a7 knockout mice demonstrated 70% lower body weights, 87% lower plasma IGF-1 concentrations and delayed skeletal development. Because poor survival prevents evaluation of mature knockout mice, we generated a conditional Slc7a7 deletion in mature osteoblasts or mesenchymal cells of the osteo-chondroprogenitor lineage, but no differences in bone architecture were observed. Overall, global Slc7a7 deficiency caused growth failure with low plasma IGF-1 concentrations and delayed skeletal development, but Slc7a7 deficiency in the osteoblastic lineage was not a major contributor to these phenotypes. Future studies utilizing additional tissue-specific Slc7a7 knockout models may help dissect cell-autonomous and non-cell-autonomous mechanisms underlying phenotypes in LPI.
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Affiliation(s)
- Bridget M. Stroup
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Xiaohui Li
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Sara Ho
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Haonan Zhouyao
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Yuqing Chen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Safa Ani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Brian Dawson
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Zixue Jin
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Ronit Marom
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Texas Children's Hospital, Houston, TX 77030, USA
| | - Ming-Ming Jiang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Isabel Lorenzo
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Daniel Rosen
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Denise Lanza
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Nathalie Aceves
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Sara Koh
- Rice University, Houston, TX 77005, USA
| | - John R. Seavitt
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jason D. Heaney
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Brendan Lee
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lindsay C. Burrage
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Texas Children's Hospital, Houston, TX 77030, USA
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2
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Avci Durmusalioglu E, Isik E, Ayyildiz Emecen D, Goksen D, Ozen S, Onay H, Kose M, Atik T, Darcan S, Cogulu O, Ozkinay F. The utility of reverse phenotyping: a case of lysinuric protein intolerance presented with childhood osteoporosis. J Pediatr Endocrinol Metab 2021; 34:957-960. [PMID: 33823103 DOI: 10.1515/jpem-2021-0018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 02/18/2021] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Childhood osteoporosis is often a consequence of a chronic disease or its treatment. Lysinuric protein intolerance (LPI), a rare secondary cause of the osteoporosis, is an autosomal recessive disorder with clinical features ranging from minimal protein intolerance to severe multisystemic involvement. We report a case diagnosed to have LPI using a Next Generation Sequencing (NGS) panel and evaluate the utility of reverse phenotyping. CASE PRESENTATION A fifteen-year-old-boy with an initial diagnosis of osteogenesis imperfecta, was referred due to a number of atypical findings accompanying to osteoporosis such as splenomegaly and bicytopenia. A NGS panel (TruSight One Sequencing Panel) was performed and a novel homozygous mutation of c.257G>A (p.Gly86Glu) in the SLC7A7 gene (NM_001126106.2), responsible for LPI, was detected. The diagnosis was confirmed via reverse phenotyping. CONCLUSIONS Reverse phenotyping using a multigene panel shortens the diagnostic process.
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Affiliation(s)
- Enise Avci Durmusalioglu
- Pediatric Genetics Subdivision, Department of Pediatrics, Faculty of Medicine, Ege University, Izmir, Turkey
| | - Esra Isik
- Pediatric Genetics Subdivision, Department of Pediatrics, Faculty of Medicine, Ege University, Izmir, Turkey
| | - Durdugul Ayyildiz Emecen
- Pediatric Genetics Subdivision, Department of Pediatrics, Faculty of Medicine, Ege University, Izmir, Turkey
| | - Damla Goksen
- Department of Pediatric Endocrinology and Diabetes, Faculty of Medicine, Ege University, Izmir, Turkey
| | - Samim Ozen
- Department of Pediatric Endocrinology and Diabetes, Faculty of Medicine, Ege University, Izmir, Turkey
| | - Huseyin Onay
- Department of Medical Genetics, Faculty of Medicine, Ege University, Izmir, Turkey
| | - Melis Kose
- Pediatric Genetics Subdivision, Department of Pediatrics, Faculty of Medicine, Ege University, Izmir, Turkey
| | - Tahir Atik
- Pediatric Genetics Subdivision, Department of Pediatrics, Faculty of Medicine, Ege University, Izmir, Turkey
| | - Sukran Darcan
- Department of Pediatric Endocrinology and Diabetes, Faculty of Medicine, Ege University, Izmir, Turkey
| | - Ozgur Cogulu
- Pediatric Genetics Subdivision, Department of Pediatrics, Faculty of Medicine, Ege University, Izmir, Turkey
| | - Ferda Ozkinay
- Pediatric Genetics Subdivision, Department of Pediatrics, Faculty of Medicine, Ege University, Izmir, Turkey
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3
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Stroup BM, Marom R, Li X, Hsu CW, Chang CY, Truong LD, Dawson B, Grafe I, Chen Y, Jiang MM, Lanza D, Green JR, Sun Q, Barrish JP, Ani S, Christiansen AE, Seavitt JR, Dickinson ME, Kheradmand F, Heaney JD, Lee B, Burrage LC. A global Slc7a7 knockout mouse model demonstrates characteristic phenotypes of human lysinuric protein intolerance. Hum Mol Genet 2020; 29:2171-2184. [PMID: 32504080 PMCID: PMC7399531 DOI: 10.1093/hmg/ddaa107] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 04/30/2020] [Accepted: 05/19/2020] [Indexed: 12/18/2022] Open
Abstract
Lysinuric protein intolerance (LPI) is an inborn error of cationic amino acid (arginine, lysine, ornithine) transport caused by biallelic pathogenic variants in SLC7A7, which encodes the light subunit of the y+LAT1 transporter. Treatments for the complications of LPI, including growth failure, renal disease, pulmonary alveolar proteinosis, autoimmune disorders and osteoporosis, are limited. Given the early lethality of the only published global Slc7a7 knockout mouse model, a viable animal model to investigate global SLC7A7 deficiency is needed. Hence, we generated two mouse models with global Slc7a7 deficiency (Slc7a7em1Lbu/em1Lbu; Slc7a7Lbu/Lbu and Slc7a7em1(IMPC)Bay/em1(IMPC)Bay; Slc7a7Bay/Bay) using CRISPR/Cas9 technology by introducing a deletion of exons 3 and 4. Perinatal lethality was observed in Slc7a7Lbu/Lbu and Slc7a7Bay/Bay mice on the C57BL/6 and C57BL/6NJ inbred genetic backgrounds, respectively. We noted improved survival of Slc7a7Lbu/Lbu mice on the 129 Sv/Ev × C57BL/6 F2 background, but postnatal growth failure occurred. Consistent with human LPI, these Slc7a7Lbu/Lbu mice exhibited reduced plasma and increased urinary concentrations of the cationic amino acids. Histopathological assessment revealed loss of brush border and lipid vacuolation in the renal cortex of Slc7a7Lbu/Lbu mice, which combined with aminoaciduria suggests proximal tubular dysfunction. Micro-computed tomography of L4 vertebrae and skeletal radiographs showed delayed skeletal development and suggested decreased mineralization in Slc7a7Lbu/Lbu mice, respectively. In addition to delayed skeletal development and delayed development in the kidneys, the lungs and liver were observed based on histopathological assessment. Overall, our Slc7a7Lbu/Lbu mouse model on the F2 mixed background recapitulates multiple human LPI phenotypes and may be useful for future studies of LPI pathology.
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Affiliation(s)
- Bridget M Stroup
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Ronit Marom
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Texas Children's Hospital, Houston, TX 77030, USA
| | - Xiaohui Li
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Chih-Wei Hsu
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Cheng-Yen Chang
- Department of Medicine-Pulmonary, Baylor College of Medicine, Houston, TX 77030, USA
| | - Luan D Truong
- Department of Pathology and Genomic Medicine, Houston Methodist Hospital, Houston, TX 77030, USA
| | - Brian Dawson
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Ingo Grafe
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine III, Center for Healthy Aging, University Clinic, Dresden D-01307, Germany
| | - Yuqing Chen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Ming-Ming Jiang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Denise Lanza
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jennie Rose Green
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Qin Sun
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Baylor Genetics, Houston, TX 77021, USA
| | - J P Barrish
- Department of Pathology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX 77030, USA
| | - Safa Ani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Audrey E Christiansen
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - John R Seavitt
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Mary E Dickinson
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Farrah Kheradmand
- Department of Medicine-Pulmonary, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jason D Heaney
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Brendan Lee
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lindsay C Burrage
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Texas Children's Hospital, Houston, TX 77030, USA
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4
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Kashoor I, Batlle D. Proximal renal tubular acidosis with and without Fanconi syndrome. Kidney Res Clin Pract 2019; 38:267-281. [PMID: 31474092 PMCID: PMC6727890 DOI: 10.23876/j.krcp.19.056] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 06/13/2019] [Accepted: 06/19/2019] [Indexed: 01/02/2023] Open
Abstract
Proximal renal tubular acidosis (RTA) is caused by a defect in bicarbonate (HCO3−) reabsorption in the kidney proximal convoluted tubule. It usually manifests as normal anion-gap metabolic acidosis due to HCO3− wastage. In a normal kidney, the thick ascending limb of Henle’s loop and more distal nephron segments reclaim all of the HCO3− not absorbed by the proximal tubule. Bicarbonate wastage seen in type II RTA indicates that the proximal tubular defect is severe enough to overwhelm the capacity for HCO3− reabsorption beyond the proximal tubule. Proximal RTA can occur as an isolated syndrome or with other impairments in proximal tubular functions under the spectrum of Fanconi syndrome. Fanconi syndrome, which is characterized by a defect in proximal tubular reabsorption of glucose, amino acids, uric acid, phosphate, and HCO3−, can occur due to inherited or acquired causes. Primary inherited Fanconi syndrome is caused by a mutation in the sodium-phosphate cotransporter (NaPi-II) in the proximal tubule. Recent studies have identified new causes of Fanconi syndrome due to mutations in the EHHADH and the HNF4A genes. Fanconi syndrome can also be one of many manifestations of various inherited systemic diseases, such as cystinosis. Many of the acquired causes of Fanconi syndrome with or without proximal RTA are drug-induced, with the list of causative agents increasing as newer drugs are introduced for clinical use, mainly in the oncology field.
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Affiliation(s)
- Ibrahim Kashoor
- Division of Nephrology and Hypertension, Department of Medicine, The Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Daniel Batlle
- Division of Nephrology and Hypertension, Department of Medicine, The Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
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5
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Abstract
Inborn errors of metabolism encompass a wide spectrum of disorders, frequently affecting bone. The most important metabolic disorders that primarily influence calcium or phosphate balance, resulting in skeletal pathology, are hypophosphatemic rickets and hypophosphatasia. Conditions involving bone marrow or affecting skeletal growth and development are mainly the lysosomal storage disorders, in particular the mucopolysaccharidoses. In these disorders skeletal abnormalities are often the presenting symptom and early recognition and intervention improves outcome in many of these diseases. Many disorders of intermediary metabolism may impact bone health as well, resulting in higher frequencies of osteopenia and osteoporosis. In these conditions factors contributing to the reduced bone mineralization can be the disorder itself, the strict dietary treatment, reduced physical activity or sunlight exposure and/or early ovarian failure. Awareness of these primary or secondary bone problems amongst physicians treating patients with inborn errors of metabolism is of importance for optimization bone health and recognition of skeletal complications.
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Affiliation(s)
- M Langeveld
- Department of Endocrinology and Metabolism, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, the Netherlands.
| | - C E M Hollak
- Department of Endocrinology and Metabolism, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, the Netherlands
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Estève E, Krug P, Hummel A, Arnoux JB, Boyer O, Brassier A, de Lonlay P, Vuiblet V, Gobin S, Salomon R, Piètrement C, Bonnefont JP, Servais A, Galmiche L. Renal involvement in lysinuric protein intolerance: contribution of pathology to assessment of heterogeneity of renal lesions. Hum Pathol 2017; 62:160-169. [PMID: 28087478 DOI: 10.1016/j.humpath.2016.12.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 11/25/2016] [Accepted: 12/20/2016] [Indexed: 12/12/2022]
Abstract
Lysinuric protein intolerance (LPI) is a rare autosomal recessive disease caused by mutations in the SLC7A7 gene encoding the light subunit of a cationic amino acid transporter. Symptoms mimic primary urea cycle defects but dysimmune symptoms are also described. Renal involvement in LPI was first described in the 1980s. In 2007, it appeared that it could concern as much as 75% of LPI patients and could lead to end-stage renal disease. The most common feature is proximal tubular dysfunction and nephrocalcinosis but glomerular lesions are also reported. However, very little is known regarding histological lesions associated with LPI. We gathered every kidney biopsy of LPI-proven patients in our highly specialized pediatric and adult institution. Clinical, biological, and histological information was analyzed. Five LPI patients underwent kidney biopsy in our institution between 1986 and 2015. Clinically, 4/5 presented with proximal tubular dysfunction and 3/5 with nephrotic range proteinuria. Histology showed unspecific tubulointerstitial lesions and nephrocalcinosis in 3/5 biopsies and marked peritubular capillaritis in one child. Glomerular lesions were heterogeneous: lupus-like-full house membranoproliferative glomerulonephritis (MPGN) in one child evolved towards monotypic IgG1κ MPGN sensitive to immunomodulators. One patient presented with glomerular non-AA non-AL amyloidosis. Renal biopsy is particularly relevant in LPI presenting with glomerular symptoms for which variable histological lesions can be responsible, implying specific treatment and follow-up.
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Affiliation(s)
- Emmanuel Estève
- Pathology Department Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France.
| | - Pauline Krug
- Pediatric Nephrology Department, Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France.
| | - Aurélie Hummel
- Nephrology Department, Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France.
| | - Jean-Baptiste Arnoux
- Metabolic Diseases Department, Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France.
| | - Olivia Boyer
- Pediatric Nephrology Department, Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France.
| | - Anais Brassier
- Metabolic Diseases Department, Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France.
| | - Pascale de Lonlay
- Metabolic Diseases Department, Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France.
| | - Vincent Vuiblet
- Nephrology and Renal Transplantation Department and Pathology Department, Centre Hospitalier et Universitaire de Reims, Reims, France.
| | - Stéphanie Gobin
- Molecular Genetics Department, Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France
| | - Rémi Salomon
- Pediatric Nephrology Department, Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France.
| | - Christine Piètrement
- Department of Paediatrics, Nephrology Paediatric Unit, Centre Hospitalier et Universitaire de Reims, Reims, France.
| | - Jean-Paul Bonnefont
- Molecular Genetics Department, Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France
| | - Aude Servais
- Nephrology Department, Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France.
| | - Louise Galmiche
- Pathology Department Hôpital Necker-Enfants Malades, Assistance Publique, Hôpitaux de Paris, Université Sorbonne Paris Cité, 75015, Paris, France.
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7
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Riccio E, Pisani A. Fanconi syndrome with lysinuric protein intolerance. Clin Kidney J 2014; 7:599-601. [PMID: 25859380 PMCID: PMC4389143 DOI: 10.1093/ckj/sfu107] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 09/22/2014] [Indexed: 11/15/2022] Open
Abstract
We present the case of a 9-year-old child with lysinuric protein intolerance and Fanconi syndrome. She was referred to our hospital with a persistent metabolic acidosis and polyuria. Renal investigations revealed all laboratory signs of Fanconi syndrome, with glucosuria, generalized aminoaciduria, phosphaturia and severe hypercalciuria. The diagnosis of Fanconi syndrome was confirmed by a renal biopsy that showed extensive lesions of proximal tubular epithelial cells with vacuolation of these cells and a sloughing of the brush border.
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Affiliation(s)
- Eleonora Riccio
- Department of Public Health , University Federico II , Naples , Italy
| | - Antonio Pisani
- Department of Public Health , University Federico II , Naples , Italy
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8
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van Vliet D, Derks TGJ, van Rijn M, de Groot MJ, MacDonald A, Heiner-Fokkema MR, van Spronsen FJ. Single amino acid supplementation in aminoacidopathies: a systematic review. Orphanet J Rare Dis 2014; 9:7. [PMID: 24422943 PMCID: PMC3895659 DOI: 10.1186/1750-1172-9-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 12/27/2013] [Indexed: 12/15/2022] Open
Abstract
Aminoacidopathies are a group of rare and diverse disorders, caused by the deficiency of an enzyme or transporter involved in amino acid metabolism. For most aminoacidopathies, dietary management is the mainstay of treatment. Such treatment includes severe natural protein restriction, combined with protein substitution with all amino acids except the amino acids prior to the metabolic block and enriched with the amino acid that has become essential by the enzymatic defect. For some aminoacidopathies, supplementation of one or two amino acids, that have not become essential by the enzymatic defect, has been suggested. This so-called single amino acid supplementation can serve different treatment objectives, but evidence is limited. The aim of the present article is to provide a systematic review on the reasons for applications of single amino acid supplementation in aminoacidopathies treated with natural protein restriction and synthetic amino acid mixtures.
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Affiliation(s)
| | | | | | | | | | | | - Francjan J van Spronsen
- Department of Metabolic Diseases, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
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9
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Posey JE, Burrage LC, Miller MJ, Liu P, Hardison MT, Elsea SH, Sun Q, Yang Y, Willis AS, Schlesinger AE, Bacino CA, Lee BH. Lysinuric Protein Intolerance Presenting with Multiple Fractures. Mol Genet Metab Rep 2014; 1:176-183. [PMID: 25419514 PMCID: PMC4235665 DOI: 10.1016/j.ymgmr.2014.03.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Lysinuric protein intolerance (LPI) is a rare autosomal recessive inborn error of metabolism caused by mutations in SLC7A7, which encodes a component of the dibasic amino acid transporter found in intestinal and renal tubular cells. Patients typically present with vomiting, diarrhea, irritability, failure to thrive, and symptomatic hyperammonemia after protein-rich meals. Long-term complications may include pulmonary alveolar proteinosis, renal disease, and osteoporosis. We present a 5-year-old male who was followed in our skeletal dysplasia clinic for 3 years for multiple fractures, idiopathic osteoporosis, and short stature in the absence of typical features of LPI. Whole exome sequencing performed to determine the etiology of the osteoporosis and speech delay identified a nonsense mutation in SLC7A7. Chromosome microarray analysis identified a deletion involving the second allele of the same gene, and biochemical analysis supported the diagnosis of LPI. Our patient's atypical presentation underscores the importance of maintaining a high index of suspicion for LPI in patients with unexplained fractures and idiopathic osteoporosis, even in the absence of clinical symptoms of hyperammonemia after protein rich meals or other systemic features of classical LPI. This case further demonstrates the utility of whole exome sequencing in diagnosis of unusual presentations of rare disorders for which early intervention may modify the clinical course.
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Affiliation(s)
- Jennifer E Posey
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA
| | - Lindsay C Burrage
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA
| | - Marcus J Miller
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA
| | - Pengfei Liu
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA
| | - Matthew T Hardison
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA
| | - Sarah H Elsea
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA
| | - Qin Sun
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA
| | - Yaping Yang
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA
| | - Alecia S Willis
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA
| | - Alan E Schlesinger
- Department of Pediatric Radiology, Texas Children's Hospital, 6701 Fannin, Suite 470, Houston, TX, 77030, USA
| | - Carlos A Bacino
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA
| | - Brendan H Lee
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA ; Howard Hughes Medical Institute, Houston, TX, USA
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10
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Alfadhel M, Al-Thihli K, Moubayed H, Eyaid W, Al-Jeraisy M. Drug treatment of inborn errors of metabolism: a systematic review. Arch Dis Child 2013; 98:454-61. [PMID: 23532493 PMCID: PMC3693126 DOI: 10.1136/archdischild-2012-303131] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
BACKGROUND The treatment of inborn errors of metabolism (IEM) has seen significant advances over the last decade. Many medicines have been developed and the survival rates of some patients with IEM have improved. Dosages of drugs used for the treatment of various IEM can be obtained from a range of sources but tend to vary among these sources. Moreover, the published dosages are not usually supported by the level of existing evidence, and they are commonly based on personal experience. METHODS A literature search was conducted to identify key material published in English in relation to the dosages of medicines used for specific IEM. Textbooks, peer reviewed articles, papers and other journal items were identified. The PubMed and Embase databases were searched for material published since 1947 and 1974, respectively. The medications found and their respective dosages were graded according to their level of evidence, using the grading system of the Oxford Centre for Evidence-Based Medicine. RESULTS 83 medicines used in various IEM were identified. The dosages of 17 medications (21%) had grade 1 level of evidence, 61 (74%) had grade 4, two medications were in level 2 and 3 respectively, and three had grade 5. CONCLUSIONS To the best of our knowledge, this is the first review to address this matter and the authors hope that it will serve as a quickly accessible reference for medications used in this important clinical field.
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Affiliation(s)
- Majid Alfadhel
- Division of Genetics, Department of Pediatrics, King Saud bin Abdulaziz University for Health Sciences, King Abdulaziz Medical City, PO Box 22490, Riyadh 11426, Saudi Arabia.
| | - Khalid Al-Thihli
- Genetics and Developmental Medicine Clinic, Sultan Qaboos University Hospital, Muscat, Sultanate ofOman
| | - Hiba Moubayed
- Pharmaceutical Care Services, Division of Clinical Pharmacy, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - Wafaa Eyaid
- Division of Genetics, Department of Pediatrics, King Saud bin Abdulaziz University for Health Sciences, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - Majed Al-Jeraisy
- Pharmaceutical Care Services, Division of Clinical Pharmacy, King Abdulaziz Medical City, Riyadh, Saudi Arabia
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11
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Tanner LM, Näntö-Salonen K, Venetoklis J, Kotilainen S, Niinikoski H, Huoponen K, Simell O. Nutrient intake in lysinuric protein intolerance. J Inherit Metab Dis 2007; 30:716-21. [PMID: 17588131 DOI: 10.1007/s10545-007-0558-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2007] [Revised: 04/25/2007] [Accepted: 04/27/2007] [Indexed: 02/07/2023]
Abstract
Lysinuric protein intolerance (LPI) is a rare autosomal recessive disorder characterized by defective transport of cationic amino acids. Poor intestinal absorption and increased renal loss of arginine, ornithine and lysine lead to low plasma concentrations of these amino acids and, subsequently, to impaired urea cycle function. The patients therefore have decreased nitrogen tolerance, which may lead to hyperammonaemia after ingestion of normal amounts of dietary protein. As a protective mechanism, most patients develop strong aversion to protein-rich foods early in life. Oral supplementation with citrulline, which is absorbed normally and metabolized to arginine and ornithine, improves protein tolerance to some extent, as do sodium benzoate and sodium phenylbutyrate also used by some patients. Despite effective prevention of hyperammonaemia, the patients still consume a very restricted diet, which may be deficient in energy, essential amino acids and some vitamins and minerals. To investigate the potential nutritional problems of patients with lysinuric protein intolerance, 77 three- to four-day food records of 28 Finnish LPI patients aged 1.5-61 years were analysed. The data suggest that the patients are clearly at risk for many nutritional deficiencies, which may contribute to their symptoms. Their diet is highly deficient in calcium, vitamin D, iron and zinc. Individualized nutritional supplementation accompanied by regular monitoring of dietary intake is therefore an essential part of the treatment of LPI.
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Affiliation(s)
- L M Tanner
- Department of Pediatrics, University of Turku, Kiinamyllynkatu 4-8, 20520, Turku, Finland.
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12
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Lutgens L, Lambin P. Biomarkers for radiation-induced small bowel epithelial damage: An emerging role for plasma Citrulline. World J Gastroenterol 2007; 13:3033-42. [PMID: 17589917 PMCID: PMC4172608 DOI: 10.3748/wjg.v13.i22.3033] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Reduction of cancer treatment-induced mucosal injury has been recognized as an important target for improving the therapeutic ratio as well as reducing the economic burden associated with these treatment related sequellae. Clinical studies addressing this issue are hampered by the fact that specific objective parameters, which enable monitoring of damage in routine clinical practice, are lacking. This review summarizes pros and cons of currently available endpoints for intestinal injury. The metabolic background and characteristics of plasma citrulline, a recently investigated biomarker specifically for small intestinal injury, are discussed in more detail.
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Affiliation(s)
- Ludy Lutgens
- Department of Radiation Oncology (Maastro), GROW Research Institute, University of Maastricht, Tanslaan 12, 6202 AZ Maastricht, The Netherlands.
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13
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Tanner LM, Näntö-Salonen K, Niinikoski H, Huoponen K, Simell O. Long-term oral lysine supplementation in lysinuric protein intolerance. Metabolism 2007; 56:185-9. [PMID: 17224331 DOI: 10.1016/j.metabol.2006.09.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Accepted: 09/07/2006] [Indexed: 02/04/2023]
Abstract
In lysinuric protein intolerance (LPI), defective transport of cationic amino acids at the basolateral membrane of the polar epithelial cells in the intestine and renal tubules leads to decreased intestinal absorption and excessive renal loss of lysine, arginine, and ornithine. Citrulline supplementation partially restores the function of the urea cycle that is impaired by deficiency of arginine and ornithine, but does not correct the chronic lysine deficiency. Previous attempts to supplement lysine orally have been hindered by profuse diarrhea, probably caused by excess lysine remaining unabsorbed in the gut. However, individually adjusted minute doses of L-lysine hydrochloride at mealtimes are tolerated well, but the long-term benefits of this therapy remain unknown. The aim of the study was to investigate the long-term benefits and possible adverse effects of oral lysine supplementation in patients with LPI. Supplementation of meals with low doses of oral lysine improved fasting plasma lysine concentrations in 27 Finnish patients with LPI without causing hyperammonemia or other recognizable side effects during 12 months of follow-up. In conclusion, low-dose oral lysine supplementation is potentially beneficial to patients with LPI and can be started safely at an early age.
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Affiliation(s)
- Laura M Tanner
- Department of Pediatrics, University of Turku, 20520 Turku, Finland.
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14
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Kauffman RP, Overton TH, Shiflett M, Jennings JC. Osteoporosis in children and adolescent girls: case report of idiopathic juvenile osteoporosis and review of the literature. Obstet Gynecol Surv 2001; 56:492-504. [PMID: 11496161 DOI: 10.1097/00006254-200108000-00023] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
UNLABELLED The diagnosis and treatment of osteoporosis is an important aspect of gynecologic training and practice. Idiopathic juvenile osteoporosis (IJO) is a rare disease of children and adolescents that resolves after the onset of puberty. A case report is presented and current methods of diagnosis and treatment of IJO are discussed as well as the differential diagnosis. A MEDLINE search was performed of the following terms: idiopathic juvenile osteoporosis, pediatric osteoporosis, adolescent osteoporosis, bisphosphonates pediatric adolescent, and pregnancy osteoporosis, and references from bibliographies of selected papers were used as well. All papers in English, French, and German are considered in this review. There were 114 papers selected as relevant to the topic. Data relevant to the diagnosis, pathogenesis, methods of imaging, laboratory evaluation, differential diagnosis, and treatment of IJO are presented. IJO is a diagnosis of exclusion in the pediatric and adolescent patient with osteoporosis. Although bone density gradually improves after the onset of puberty, treatment of currently affected children and adolescents involves activity restriction, calcium, vitamin D, and bisphosphonate therapy. Future reproductive concerns are discussed and areas requiring additional study are reviewed. TARGET AUDIENCE Obstetricians & Gynecologists, Family Physicians LEARNING OBJECTIVES After completion of this article, the reader will be able to describe the condition idiopathic juvenile osteoporosis, compare the clinical features of this condition to other similar conditions, outline the diagnostic workup of a child with this condition, and list the potential therapeutic options for a patient with idiopathic juvenile osteoporosis.
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Affiliation(s)
- R P Kauffman
- Department of Obstetrics and Gynecology, Texas Tech University Health Sciences Center, Amarillo, 79106, USA.
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15
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Parto K, Penttinen R, Paronen I, Pelliniemi L, Simell O. Osteoporosis in lysinuric protein intolerance. J Inherit Metab Dis 1993; 16:441-50. [PMID: 8412005 DOI: 10.1007/bf00710296] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Lysinuric protein intolerance (LPI) is an autosomal recessive disease characterized by defective transport of cationic amino acids. Patients have an increased incidence of fractures and their skeletal radiographs show osteoporosis. The aim of the study was to characterize the osteopenia in LPI. Twenty-nine Finnish LPI patients (age range 3.7-44.4 years) were screened for parameters of bone metabolism. Morphometric analysis of bone was carried out in specimens of 9 patients. Collagen synthesis was studied with cultured skin fibroblasts (4 patients) and collagen fibril sizes (3 patients) were measured using electron microscopy. Most histological bone specimens (8/9) showed osteoporosis. Osteomalacia was excluded. Routine clinical laboratory tests were unrevealing. The concentrations of free hydroxyproline and type III procollagen N-propeptide in serum and the urinary excretion of hydroxyproline were increased in almost all patients during their growth and in about half of adult patients. Collagen synthesis in LPI fibroblast cultures was significantly decreased compared with that in age-matched controls at 5 (p < 0.01), 14 (p < 0.01) and still at 30 years (p < 0.01), whereas no difference was observed at the age of 44 years (p = N.S.). Osteoporosis in LPI might reflect defective matrix protein synthesis caused by protein deprivation and deficiency of cationic amino acids. Increased collagen turnover can also contribute to the osteoporosis.
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Affiliation(s)
- K Parto
- Department of Pediatrics, University Central Hospital, University of Turku, Finland
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16
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Carpenter TO, Shiratori T. Renal 25-hydroxyvitamin D-1 alpha-hydroxylase activity and mitochondrial phosphate transport in Hyp mice. THE AMERICAN JOURNAL OF PHYSIOLOGY 1990; 259:E814-21. [PMID: 2260650 DOI: 10.1152/ajpendo.1990.259.6.e814] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The Hyp mouse is a homologue of the X chromosome-linked human disease, familial hypophosphatemic rickets (FHR). In FHR, reduced renal tubular brush-border membrane transport of phosphate results in hypophosphatemia and rickets. Both humans with FHR and Hyp mice have abnormal regulation of 25-hydroxyvitamin D-1 alpha-hydroxylase (1 alpha-hydroxylase), a mitochondrial enzyme found in proximal renal tubular cell epithelia, the apparent site of defective brush-border membrane phosphate transport. No common pathophysiology for these defects has been demonstrated. We hypothesized that phosphate transport may be present in renal mitochondria from Hyp mice and that its regulation may be deranged in parallel with the mitochondrial 1 alpha-hydroxylase. Using inhibitor-stop techniques described for measurement of phosphate transport in liver mitochondria, we examined mitochondria in normal and Hyp mouse kidney and found them to be comparable. We performed manipulations known to alter 1 alpha-hydroxylase differentially in normal and Hyp mice, i.e., phosphorus deprivation and phosphorus loading, and found no effect on mitochondrial phosphate transport. We also subjected Hyp and normal mice to calcium and vitamin D deprivation; this maneuver resulted in no significant changes in mitochondrial phosphate transport in Hyp or normal mice but confirmed the earlier observation that 1 alpha-hydroxylase activity is stimulated to a greater degree in normal mice than Hyp mice after this diet. Furthermore, administration of 1,25-hydroxyvitamin D3 depresses 1 alpha-hydroxylase activity in mitochondria from both normal and Hyp mice but has no effect on mitochondrial phosphate transport. We conclude that the mechanism of abnormal vitamin D metabolism in Hyp mice is not related to a primary defect in renal mitochondrial phosphate transport.
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Affiliation(s)
- T O Carpenter
- Department of Pediatrics (Endocrinology), Yale University School of Medicine, New Haven, Connecticut 06510
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17
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Shaw PJ, Dale G, Bates D. Familial lysinuric protein intolerance presenting as coma in two adult siblings. J Neurol Neurosurg Psychiatry 1989; 52:648-51. [PMID: 2732736 PMCID: PMC1032181 DOI: 10.1136/jnnp.52.5.648] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Lysinuric protein intolerance (LPI) is an inborn error of metabolism which usually presents in infancy with failure to thrive and vomiting. Two patients are described who presented in adult life with hyperammonaemic coma due to LPI. Both had been underweight and had had intermittent gastrointestinal symptoms during childhood. They were of normal intellect and had maintained good health, until presentation in their thirties, by unconscious dietary protein avoidance. The diagnosis of LPI should be considered in patients who present with obscure relapsing coma associated with hyperammonaemia. Considerable clinical improvement may result from dietary protein restriction and citrulline supplementation.
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Affiliation(s)
- P J Shaw
- Department of Neurology, University of Newcastle upon Tyne, UK
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18
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Perry TL, Hansen S, Booth FA, Penn AM, Jones K, Dilling LA. An unusual aminoacidopathy associated with mitochondrial encephalomyopathy. J Inherit Metab Dis 1989; 12:23-32. [PMID: 2501579 DOI: 10.1007/bf01805527] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Five patients from two unrelated pedigrees are affected by an inherited form or forms of mitochondrial encephalomyopathy in which the exact site of the block in the respiratory chain has yet to be identified. All five patients regularly exhibit an unusual aminoacidopathy evident both in fasting plasma and in CSF. Alanine concentrations are elevated, reflecting high tissue pyruvate and lactate levels. Concentrations of the four essential amino acids threonine, methionine, tryptophan and lysine are substantially reduced, as are those of citrulline, ornithine and arginine. This pattern of amino-acid deficiency is apparently not due to failure to absorb the dibasic amino acids, to any abnormality of the urea cycle, to excessive synthesis and turnover of creatine, or to protein malnutrition. The aminoacidopathy presumably is a metabolic consequence of one or more impairments in the electron transport chain in mitochondria. A detailed explanation of its aetiology needs to be sought.
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Affiliation(s)
- T L Perry
- Department of Pharmacology & Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, Canada
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19
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Lysinuric protein intolerance: a rare cause of childhood osteoporosis. Nutr Rev 1986; 44:110-3. [PMID: 3083306 DOI: 10.1111/j.1753-4887.1986.tb07598.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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Abstract
We reviewed the natural history and differential diagnosis of ornithine transcarbamylase deficiency (an X-linked inborn error of urea synthesis) in 13 symptomatic female heterozygotes. The patients presented as early as the first week of life or as late as the sixth year. The most common symptoms before diagnosis were nonspecific: episodic extreme irritability (100 percent), episodic vomiting and lethargy (100 percent), protein avoidance (92 percent), ataxia (77 percent), Stage II coma (46 percent), delayed physical growth (38 percent), developmental delay (38 percent), and seizures (23 percent). Including the proband, 42 percent of the female members of the 13 families studied had symptoms. The median interval between the onset of major symptoms (vomiting and lethargy, seizures, and coma) and diagnosis was 16 months (range, 1 to 142). Five patients had IQ scores below 70 at the time of diagnosis. We suggest that careful evaluation of the family history, the dietary history, the episodic nature of the nonspecific symptoms, the response of these symptoms to the withdrawal of protein, and their frequent onset at the time of weaning from breast milk will permit early diagnosis and might thereby reduce the risk of death or neurologic impairment in female patients with partial ornithine transcarbamylase deficiency.
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Abstract
We surveyed both normal children and patient populations to identify the effects of metabolic bone disease and impaired renal function on serum levels of osteocalcin, a vitamin K-dependent protein synthesized in bone. Cord blood osteocalcin was nearly double that of maternal osteocalcin, but there was no correlation between the two. Infants with Apgar scores less than or equal to 7 had a lower mean serum osteocalcin value (8.7 ng/ml, n = 8) than did those with scores of 8 to 10 (16.6 ng/ml, n = 38). Serum osteocalcin elevation coincided with the pubertal growth spurt. In boys, levels decreased to adult values by 18 years of age, as do other indices of bone metabolism; in girls, the levels decreased earlier and had a less pronounced maximum. In children with renal failure, osteocalcin was substantially increased, presumably because of diminished renal clearance of the protein. Children receiving peritoneal dialysis, however, had mean serum concentrations less than half of those seen in children receiving hemodialysis (117 vs 328 ng/ml). The peritoneal dialysate contained significant amounts of osteocalcin, but none was detectable in hemodialysate. Correlation between bone disease and serum osteocalcin was evident in a longitudinal study of one patient with renal failure. Children with various forms of rickets had elevated osteocalcin levels; hypoparathyroidism and osteoporosis were accompanied by variable changes. Serum osteocalcin holds promise as a useful marker of subacute changes in bone metabolism.
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