Disease characteristics. Clinical features of atelosteogenesis type 2 (AO2) include rhizomelic limb shortening with normal-sized skull, hitchhiker thumbs, small chest, protuberant abdomen, cleft palate, and distinctive facial features (midface hypoplasia, depressed nasal bridge, epicanthus, micrognathia). Other typical findings are ulnar deviation of the fingers, gap between the first and second toes, and clubfoot. AO2 is lethal at birth or shortly thereafter because of pulmonary hypoplasia and tracheobronchomalacia.
Diagnosis/testing. The diagnosis of AO2 rests on a combination of clinical, radiologic, and histopathologic features. SLC26A2 (DTDST) is the only gene currently known to be associated with AO2. The diagnosis can be confirmed by molecular genetic testing of SLC26A2, which is clinically available.
Management. Treatment of manifestations: palliative care for liveborns.
Genetic counseling. AO2 is inherited in an autosomal recessive manner. At conception, each sib of a proband with AO2 has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Once an at-risk sib is known to be unaffected, the risk of his/her being a carrier is 2/3. Prenatal diagnosis for pregnancies at 25% risk is possible. Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if both disease-causing alleles in the family are known and the carrier status of the parents has been confirmed. Ultrasound examination early in pregnancy is a reasonable complement or alternative to molecular genetic prenatal diagnosis.