title: Lysinuric Protein Intolerance Presenting with Multiple Fractures.
abstract: Lysinuric protein intolerance (LPI) is a rare autosomal recessive inborn error of metabolism caused by mutations inSLC7A7, 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 inSLC7A7. 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.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA.
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Posey
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA.
authors.forename: Lindsay C
authors.initials: LC
authors.lastname: Burrage
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA.
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Miller
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Liu
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Hardison
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA.
authors.forename: Sarah H
authors.initials: SH
authors.lastname: Elsea
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA.
authors.forename: Qin
authors.initials: Q
authors.lastname: Sun
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA.
authors.forename: Yaping
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA.
authors.forename: Alecia S
authors.initials: AS
authors.lastname: Willis
authors.affiliation: Department of Pediatric Radiology, Texas Children's Hospital, 6701 Fannin, Suite 470, Houston, TX, 77030, USA.
authors.forename: Alan E
authors.initials: AE
authors.lastname: Schlesinger
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Suite R814, Houston, TX, 77030-3411, USA.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Bacino
authors.affiliation: 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.
authors.forename: Brendan H
authors.initials: BH
authors.lastname: Lee
keywords: Lysinuric protein intolerance; SLC7A7; bone fractures; osteoporosis