title: Childhood hypophosphatasia with homozygous mutation of ALPL.
abstract: OBJECTIVE
  To describe an unusual phenotype of a case with rare homozygous ALPL gene mutation that results in mild form of hypophosphatasia.
  
  
  METHODS
  Case presentation, description of biochemical profiles, genetic testing and a brief review of literature are presented.
  
  
  RESULTS
  A 13-year-old male presented with chronic left knee pain. Radiogram of the left knee indicated two oval radiolucent lesions in the femoral metaphysis. Serum alkaline phosphatase activity (17 U/L) was markedly below normal (42 to 362 U/L). Serum pyridoxal 5' phosphate (258 μg/L) was above normal (5 to 50 μg/L). Sequence analysis of ALPL gene indicated a homozygous missense mutation c.1077 C>G (p. I359M). The mutation was previously identified in a case of perinatal hypophosphatasia with severe skeletal abnormalities in contrast to the mild phenotype of the patient we present.
  
  
  CONCLUSIONS
  The case of homozygous mutation of ALPL gene but mild form of hypophosphatasia suggests that functions of the mutated protein may be modified by other factors.
authors.affiliation: Division of Pediatric Endocrinology, University of Miami, Miami, Florida.
authors.forename: Supamit
authors.initials: S
authors.lastname: Ukarapong
authors.affiliation: Department of Radiology, Children's Hospital and Medical Center of Akron, Akron, Ohio.
authors.forename: Shankar Srinivas
authors.initials: SS
authors.lastname: Ganapathy
authors.affiliation: Center for Diabetes and Endocrinology, Children's Hospital and Medical Center of Akron, Akron, Ohio.
authors.forename: Jaime
authors.initials: J
authors.lastname: Haidet
authors.affiliation: Division of Pediatric Endocrinology, University of Miami, Miami, Florida.
authors.forename: Gary
authors.initials: G
authors.lastname: Berkovitz
mesh_terms: D000293:Adolescent; D000469:Alkaline Phosphatase / Q000235:genetics*; D005260:Female; D005820:Genetic Testing; D006801:Humans; D007014:Hypophosphatasia; D008297:Male; D009154:Mutation; D020125:Mutation, Missense; D011247:Pregnancy
chemical_list: C548267:ALPL protein, human; D000469:Alkaline Phosphatase