Two Siblings with Hypophosphatasia

Two siblings with hypophosphatasia, one of whom was autopsied, were reported. The first case which was a product of a 26-year-old mother complicated by hydroamnios represented poor mineralization of the entire bones on X-ray examination and died shortly after birth. The second case weighing 1850 g delivered from the same mother had a rhizomelic micromelia and poor visualization of the skull, long bones and vertebral bones on X-ray at postmortem. The autopsy on the second case showed small thoracic cage with rachitic rosaries of ribs, membranous skull and poorly ossified vertebral and long bones. Microscopically, there was a marked disturbance of both enchondral and membranous ossifications similar to the histology of rachitis. A biochemical examination showed low alkaline phosphatase, high calcium and normal PTH in the serum. Further examination of their family revealed relatively low level of alkaline phosphatase of the parents and one of their brothers which suggsted they were carriers of hypophosphastasia. Previous reports on hypophosphatasia were reviewed and differential diagnosis of hypophosphatasia from the other congenital dwarfisms was discussed.