Asymmetric crying facies is a minor congenital anomaly caused by agenesis or hypoplasia of the depressor anguli oris muscle, one of the muscles that control the movements of the lower lip. This unilateral facial weakness is ﬁrst noticed when the infant cries or smiles, affecting only one corner of the mouth and occurs on the left side in nearly 80% of cases. It is associated with other birth defects in more than 50% of cases.
When the hypoplasia of the depressor anguli oris muscle is associated with congenital cardiac defects, the term 'Cayler cardiofacial syndrome' is used. Cayler syndrome is part of the 22q11.2 deletion syndrome.