Congenital Malformations and Complexes
Core concepts
Organize malformations by mechanism: malformation (intrinsic developmental defect), disruption (extrinsic destruction of normal tissue, e.g., amniotic band), deformation (mechanical distortion), and dysplasia (abnormal tissue organization). Know major complexes and associations-VACTERL, CHARGE, and specific sequences-and the distinction between syndromic and isolated malformations.
Be able to reason about common system-specific defects: neural tube defects and their prevention with folate; congenital heart disease categories (septal, conotruncal, obstructive); renal anomalies (agenesis, dysplasia, obstruction); and gastrointestinal atresias. Understand how a single early defect can cascade into a sequence (e.g., tracheoesophageal fistula with esophageal atresia).
Traps
Examiners blur association (VACTERL) with syndrome; VACTERL has no single known cause. Another trap: confusing amniotic band disruption with a genetic limb malformation-bands produce asymmetric, irregular defects. Also, do not assume all congenital heart disease presents at birth; many lesions present when the ductus closes.
Worked example / rule of thumb
A newborn with vertebral anomalies, anal atresia, cardiac defect, tracheoesophageal fistula, renal anomaly, and limb defects fits VACTERL-describe as an association and screen the components. Rule of thumb: "Malformation = built wrong; disruption = broken; deformation = molded; dysplasia = abnormal tissue."