Project description:Lysinuric protein intolerance (LPI) is an autosomal recessive disease characterized by defective transport of cationic amino acids and by hyperammonemia. Linkage analysis in 20 Finnish LPI families assigned the LPI gene locus to the proximal long arm of chromosome 14. Recombinations placed the locus between framework markers D14S72 and MYH7, a 10-cM interval in which the markers D14S742, D14S50, D14S283, and TCRA showed no recombinations with the phenotype. The phenotype was in highly significant linkage disequilibrium with markers D14S50, D14S283, and TCRA. The strongest allelic association obtained with marker TCRA, resulting in a P(excess) value of .98, suggests that the LPI gene locus lies in close proximity to this marker, probably within a distance of < 100 kb.
Project description: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.
Project description: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.
Project description:Lysinuric protein intolerance (LPI) is a rare autosomal disease caused by defective cationic amino acid (CAA) transport due to mutations in SLC7A7, which encodes for the y+LAT1 transporter. LPI patients suffer from a wide variety of symptoms, which range from failure to thrive, hyperammonemia, and nephropathy to pulmonar alveolar proteinosis (PAP), a potentially life-threatening complication. Hyperammonemia is currently prevented by citrulline supplementation. However, the full impact of this treatment is not completely understood. In contrast, there is no defined therapy for the multiple reported complications of LPI, including PAP, for which bronchoalveolar lavages do not prevent progression of the disease. The lack of a viable LPI model prompted us to generate a tamoxifen-inducible Slc7a7 knockout mouse (Slc7a7-/-). The Slc7a7-/- model resembles the human LPI phenotype, including malabsorption and impaired reabsorption of CAA, hypoargininemia and hyperammonemia. Interestingly, the Slc7a7-/- mice also develops PAP and neurological impairment. We observed that citrulline treatment improves the metabolic derangement and survival. On the basis of our findings, the Slc7a7-/- model emerges as a promising tool to further study the complexity of LPI, including its immune-like complications, and to design evidence-based therapies to halt its progression.
Project description:An Illumina microarray analysis of the changes in the transcription of genes other than SLC7A7 in 13 Finnish patients with lysinuric protein intolerance (LPI). The patient samples were compared to a pooled sample of 10 sex and age-matched controls which was hybridised twice on the microarrays (Control A and Control B).
Project description:BACKGROUND:Lysinuric protein intolerance (LPI) is a rare autosomal recessive disorder characterized by deficient membrane transport of cationic amino acids. It is caused by pathogenic variants in SLC7A7, resulting in impairment of intestinal import and renal proximal tubule loss of the affected amino acids. LPI typically presents with gastrointestinal symptoms, such as vomiting, diarrhea, and failure to thrive. CASE REPORT:A 4-year-old African-American boy presented with multiple respiratory tract infections, weight loss in the setting of chronic diarrhea and worsening abdominal distention, and multiple episodes of rectal prolapse. Development was unaffected. Laboratory examination demonstrated mild anemia, hypokalemia and hypoalbuminemia, transaminitis, and normal ammonia. Initial urine amino acid analysis did not show major elevations of lysine and ornithine, often lower than expected in the setting of malnutrition. Upon initiation of total parenteral nutrition (TPN), his urine amino acids showed a characteristic profile of dibasic aminoaciduria. CONCLUSIONS:Failure to thrive, chronic diarrhea, and hepatomegaly should raise suspicion for LPI. Urine amino acids can be normal in this condition in the setting of malnutrition, a common complication of the disease. Additionally, it has been previously shown that the plasma arginine and ornithine concentration is higher in LPI subjects.
Project description:Maternal lysinuric protein intolerance (LPI) is associated with increased risk of anemia, toxemia, and retarded growth in fetus during pregnancy, and bleeding complications during delivery. There has been limited number of reports about pregnancy and outcomes of lactation in LPI. Here we present pregnancy and lactation outcomes in a Turkish patient with LPI. In the pregnancy and delivery period, her metabolic status was stable with protein-restricted diet and citrulline. Pathological examination of the placenta revealed multifocal placental infarcts. A successful outcome was achieved with well-controlled anemia, thrombocytopenia despite hemophagocytosis in bone marrow, and placental infarcts during pregnancy. The baby was exclusively breastfed for 6 months. His growth and development was normal. Mild proteinuria started at the fourth month of the delivery. Our case report showed the importance of follow-up of these patients in terms of placental pathologies during pregnancy and for other complications during lactation period.
Project description:Lysinuric protein intolerance (LPI) is a rare autosomal recessive metabolic disorder, caused by defective transport of cationic amino acids at the basolateral membrane of epithelial cells, typically in intestines and kidneys. The SLC7A7 gene, mutated in LPI patients, encodes the light subunit (y+LAT1) of a member of the heterodimeric amino acid transporter family.The diagnosis of LPI is difficult due to unspecific clinical features: protein intolerance, failure to thrive and vomiting after weaning. Later on, patients may present delayed growth osteoporosis, hepatosplenomegaly, muscle hypotonia and life-threatening complications such as alveolar proteinosis, haemophagocytic lymphohistiocytosis and macrophage activation syndrome. Renal involvement is also a serious complication with tubular and more rarely, glomerular lesions that may lead to end-stage kidney disease (ESKD). We report six cases of LPI followed in three different French paediatric centres who presented LPI-related nephropathy during childhood. Four of them developed chronic kidney disease during follow-up, including one with ESKD. Five developed chronic tubulopathies and one a chronic glomerulonephritis. A histological pattern of membranoproliferative glomerulonephritis was first associated with a polyclonal immunoglobulin deposition, treated by immunosuppressive therapy. He then required a second kidney biopsy after a relapse of the nephrotic syndrome; the immunoglobulin deposition was then monoclonal (IgG1 kappa). This is the first observation of an evolution from a polyclonal to a monotypic immune glomerulonephritis. Immune dysfunction potentially attributable to nitric oxide overproduction secondary to arginine intracellular trapping is a debated complication in LPI. Our results suggest all LPI patients should be monitored for renal disease regularly.
Project description:Lysinuric protein intolerance (LPI) is a rare autosomal inherited disease caused by defective cationic aminoacid transport 4F2hc/y(+)LAT-1 at the basolateral membrane of epithelial cells in the intestine and kidney. LPI is a multisystemic disease with a variety of clinical symptoms such as hepatosplenomegaly, osteoporosis, hypotonia, developmental delay, pulmonary insufficiency or end-stage renal disease. The SLC7A7 gene, which encodes the y(+)LAT-1 protein, is mutated in LPI patients. Mutation analysis of the promoter localized in intron 1 and all exons of the SLC7A7 gene was performed in 11 patients from 9 unrelated LPI families. Point mutation screening was performed by exon direct sequencing and a new multiplex ligation probe amplification (MLPA) assay was set up for large rearrangement analysis. Eleven SLC7A7-specific mutations were identified, seven of them were novel: p.L124P, p.C425R, p.R468X, p.Y274fsX21, c.625+1G>C, DelE4-E11 and DelE6-E11. The novel large deletions originated by the recombination of Alu repeats at introns 3 and 5, respectively, with the same AluY sequence localized at the SLC7A7 3' region. The novel MLPA assay is robust and valuable for LPI molecular diagnosis. Our results suggest that genomic rearrangements of SLC7A7 play a more important role in LPI than has been reported, increasing the detection rate from 5.1 to 21.4%. Moreover, the 3' region AluY repeat could be a recombination hot spot as it is involved in 38% of all SLC7A7 rearranged chromosomes described so far.
Project description:BACKGROUND:Lysinuric protein intolerance (LPI; MIM# 222700) is a rare metabolic disorder caused by a defective cationic amino acids (CAA) membrane transport leading to decreased circulating plasma CAA levels and resulting in dysfunction of the urea cycle. Short stature is commonly observed in children with LPI and has been associated with protein malnutrition. A correlation between LPI and growth hormone deficiency (GHD) has also been postulated because of the known interaction between the AA arginine, ornithine, and lysine and growth hormone (GH) secretion. Our report describes a case of GHD in an LPI patient, who has not presented a significant increase in growth velocity with recombinant-human GH (rhGH) therapy, suggesting some possible pathogenic mechanisms of growth failure. CASE PRESENTATION:The proband was a 6-year-old boy, diagnosed as suffering from LPI, erythrophagocytosis (HP) in bone marrow, and short stature. Two GH provocative tests revealed GHD. The patient started rhGH therapy and a controlled-protein diet initially with supplementation of oral arginine and then of citrulline. At 3-year follow-up, no significant increase in growth velocity and in insulin-like growth factor-1 (IGF-1) levels was observed. Inadequate nutrition and low plasmatic levels of arginine, ornithine, lysine, and HP may have contributed to his poor growth. CONCLUSION:Our case suggests that growth failure in patients with GHD and LPI treated with rhGH could have a complex and multifactorial pathogenesis. Persistently low plasmatic levels of lysine, arginine, and ornithine, associated with dietary protein and caloric restriction and systemic inflammation, could determine a defect in coupling GH to IGF-1 production explaining why GH replacement therapy is not able to significantly improve growth impairment. We hypothesize that a better understanding of growth failure pathophysiology in these patients could lead to the development of more rational strategies to treat short stature in patients with LPI.