Achondrogenesis Type 1B

Excerpt

Clinical characteristics: Clinical features of achondrogenesis type 1B (ACG1B) include extremely short limbs with short fingers and toes, hypoplasia of the thorax, protuberant abdomen, and hydropic fetal appearance caused by the abundance of soft tissue relative to the short skeleton. The face is flat, the neck is short, and the soft tissue of the neck may be thickened. Death occurs prenatally or shortly after birth.

Diagnosis/testing: The diagnosis of ACG1B is established in a proband with characteristic clinical, radiologic, and histopathologic features. Identification of biallelic pathogenic variants in SLC26A2 on molecular genetic testing can confirm the diagnosis.

Management: Treatment of manifestations: Palliative care for live-born neonates.

Genetic counseling: ACG1B is inherited in an autosomal recessive manner. If both parents are known to be heterozygous for an SLC26A2 pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of inheriting neither of the familial SLC26A2 pathogenic variants. Once the SLC26A2 pathogenic variants have been identified in an affected family member, carrier testing for at-risk relatives, prenatal testing for a pregnancy at increased risk, and preimplantation genetic testing are possible.