Related Experiment Video
Updated: Apr 26, 2026
Assessing Cellular Target Engagement by SHP2 PTPN11 Phosphatase Inhibitors
Published on: July 17, 2020
Childhood hypophosphatasia with homozygous mutation of ALPL
Supamit Ukarapong1, Shankar Srinivas Ganapathy2, Jaime Haidet3
1Division of Pediatric Endocrinology, University of Miami, Miami, Florida.
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.
Conclusion:
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.
Related Concept Videos
01:20Inborn Errors of Metabolism
02:41Lethal Alleles
Lucien Cuénot discovered lethal alleles in 1905 while studying the inheritance of coat color in mice. The agouti gene is responsible for the color of the coat in mice. This gene codes for an agouti-signaling protein, which is responsible for melanin distribution in mammals. The wild-type allele gives rise to gray-brown coat color in mice, while the mutant allele gives rise to yellow coat color. In addition to coat color, the agouti gene is associated with the yellow...
01:20The Retinoblastoma Gene
The first-ever tumor suppressor gene called Rb was identified in retinoblastoma - a rare eye tumor in children. In inherited forms of the disease, a child inherits one defective copy of the Rb gene, which predisposes them to retinoblastoma. However,...
02:30Genomic Imprinting and Inheritance
The expression of some genes depends on which parent passed the gene to the offspring, through a phenomenon known as...
01:21Huntington Disease l: Introduction
03:14Notch Signaling Pathway
The Notch gene came into the limelight in 1914 after the discovery that its mutation in Drosophila melanogaster leads to a serrated (or "notched") wing margin phenotype. It was not...