Clinical Guidance

Achondrogenesis type 1B (ACG1B), one of the most severe chondrodysplasias, is a perinatal-lethal disorder with death occurring prenatally or shortly after birth. The mechanism of the prenatal death is unknown. In the live-born neonate, death is secondary to respiratory failure and occurs shortly after birth. Fetuses with ACG1B often present in breech position. Pregnancy complications as a result of polyhydramnios may occur (e.g., maternal breathing difficulties, preterm labor). Infants with ACG1B appear hydropic with an abundance of soft tissue relative to the short skeleton. The face is flat and the neck is short with thickened soft tissue. The limbs are extremely shortened, with inturning of the feet and toes (talipes equinovarus) and brachydactyly (short stubby fingers and toes).

Diagnostic Criteria

Achondrogenesis type 1B (ACG1B) is a perinatal-lethal disorder with death occurring prenatally or shortly after birth.

Suggestive Findings

ACG1B should be suspected in individuals with the following clinical and radiographic findings.

Clinical findings

• Extremely short limbs with short fingers and toes and clubfeet

Management Guidelines

Evaluations Following Initial Diagnosis To establish the extent of disease in an individual diagnosed with achondrogenesis type 1B (ACG1B), the evaluations summarized (if not performed as part of the evaluation that led to the diagnosis) are recommended. Table 4. Recommended Evaluations Following Initial Diagnosis in Individuals with Achondrogenesis Type 1B