Discordant fetal phenotype of hypophosphatasia in two siblings

Hypophosphatasia (HPP) is an autosomal recessive metabolic disorder with impaired bone mineralization due to mutations in the ALPL gene. The genotype‐phenotype correlation of this disorder has been widely described. Here, we present two affected siblings, whose fetal phenotypes were discordant. A 31‐year‐old Japanese woman, G0P0, was referred to our institution because of fetal micromelia. After obstetric counseling, the pregnancy was terminated at 21 weeks’ gestation. Post‐mortem radiographs demonstrated severely defective mineralization of the skeleton. The calvarial, spinal, and tubular bones were mostly missing. Only the occipital bones, mandible, clavicles, ribs, one thoracic vertebra, ilia, and tibia were relatively well ossified. The radiological findings suggested lethal HPP. Genetic testing for genomic DNA extracted from the umbilical cord identified compound heterozygous mutations in the ALPL gene (c.532T>C, p.Y178H; c.1559delT, p.Leu520Argfs*86). c.532T>C was a novel variant showing no residual activity of the protein by the functional analysis. The parents were heterozygous carriers. In the next pregnancy, biometric values on fetal ultrasonography at 20 and 26 weeks’ gestation were normal. At 34 weeks, however, a small chest and shortening of distal long bones came to attention. The neonate delivered at 41 weeks showed serum ALP of <5U/L. Radiological examination showed only mild thoracic hypoplasia and metaphyseal mineralization defects of th...

Source: American Journal of Medical Genetics Part A - November 21, 2017 Category: Genetics & Stem Cells Authors: Satoru Ikenoue, Kei Miyakoshi, Tomohiro Ishii, Yu Sato, Toshimitsu Otani, Yohei Akiba, Yoshifumi Kasuga, Daigo Ochiai, Tadashi Matsumoto, Yosuke Ichihashi, Yohei Matsuzaki, Kanako Tachikawa, Toshimi Michigami, Gen Nishimura, Kazushige Ikeda, Tomonobu Hase Tags: CLINICAL REPORT Source Type: research