Among the following scenarios, which would most likely indicate DiGeorge's syndrome in a 3-month-old infant?

The indication of DiGeorge's syndrome in a 3-month-old infant is most strongly associated with an absent thymic shadow on chest X-ray. DiGeorge's syndrome, also known as 22q11.2 deletion syndrome, is characterized by a developmental defect of the third and fourth pharyngeal pouches, leading to various clinical manifestations including thymic hypoplasia or aplasia. The thymus is critical for the development of T-cells, and its absence can be visualized on a chest X-ray as a lack of a thymic shadow.

The absence of this shadow suggests a significant alteration in the infant's immune system, predisposing them to infections. Infants with DiGeorge's syndrome often exhibit other anomalies, but the absent thymic shadow is a notable and diagnostic sign that supports the diagnosis of this condition. This imaging finding, in conjunction with the clinical presentation, can help healthcare providers initiate appropriate diagnostic testing and management strategies for the infant.

In contrast, the presence of a lateral neck mass, normal feeding and growth, or high blood calcium levels do not directly relate to the typical clinical indicators of DiGeorge’s syndrome and may pertain to different diagnoses or conditions.