Prevalence:

• Hypophosphatasiais an inherited disorder that affects the development of bones and teeth. It can appear any time from before birth to adulthood.
  • Prenatal type: 1 in 100,000 births.
  • Postnatal type: 1 in 10,000 births

Ultrasound diagnosis:

• In the prebatal type there is severe micromelia, severe thoracic hypoplasia, diffuse hypomineralization (decreased echogenicity) involving all the bones except for clavicles.

Investigations:

• Detailed ultrasound examination.
• Hypophosphatasia is due to mutations in the ALPL gene which lead to the production of an abnormal version of alkaline phosphatase that cannot participate effectively in the mineralization process. The degree of malfunction varies: the severity ranges from unapparent cases diagnosed on the basis of biochemical features to the lethal cases detected in the fetus.
• If the mutation in the family is known, prenatal diagnosis is best performed by chorion villus sampling and DNA analysis.

Follow up:

• If pregnancy continues, follow-up should be standard.

Delivery:

• Standard obstetric care and delivery.

Prognosis:

• Prenatal type: lethal due to severe pulmonary hypoplasia.
• Postnatal type: can appear in childhood or adulthood. Affected children may have short stature with bowed legs or knock knees, enlarged wrist and ankle joints, and an abnormal skull shape. In adults, there is premature loss of teeth and recurrent fractures in the foot and thigh bones causing chronic pain.

Recurrence:

• Prenatal type is autosomal recessive: 25%.
• Postnatal type is either autosomal recessive or autosomal dominant: 25% or 50%