In summary, we established that (1) monoallelic EVC/EVC2 variants have incomplete penetrance and less phenotypic expressivity than biallelic ones; (2) EVC variants associate with a less severe clinical presentation than EVC2 variants, especially if they are nontruncating; (3) thoracic anomalies are usually more variable with the implicated gene/variant types; and (4) CRMP1 is the first identified potential genetic modifier of severity in EVC-associated EVC syndrome. The gene discussed is EVC2; the disease is Ellis-van Creveld syndrome.