What is the most likely diagnosis for an infant with agenesis of the forearm, low sloping shoulders, cardiac anomalies, bifid thumb, and chest wall deformities?

The most likely diagnosis of Holt-Oram syndrome is supported by the presence of multiple congenital anomalies that are characteristic of this condition. Holt-Oram syndrome is a genetic disorder primarily affecting the heart and upper limb development, typically caused by mutations in the TBX5 gene.

In infants diagnosed with Holt-Oram syndrome, manifestations can include upper limb deformations such as agenesis or hypoplasia of the forearm, which aligns with the case presented. Additionally, the condition is known for causing cardiac anomalies, which further supports the diagnosis given the infant's symptoms. The presence of a bifid thumb—an abnormality where the thumb appears split or forked—is also a classic feature associated with Holt-Oram syndrome.

Furthermore, the low sloping shoulders and chest wall deformities are consistent with the structural malformations seen in patients with this syndrome.

While the other conditions mentioned may also involve certain physical anomalies, they do not typically encompass the specific combination of forearm agenesis, heart defects, and upper limb malformations seen in Holt-Oram syndrome, thus making it the most fitting diagnosis in this scenario.