Connect a developmental finding with how it arose. Before searching for a syndrome name, ask whether the case describes altered formation, a mechanical effect, tissue damage, or several findings linked by a developmental sequence.
Use developmental terms precisely
| Term | Teaching definition |
|---|---|
| Malformation | A structural difference arising during initial formation |
| Deformation | A change in form or position associated with mechanical forces |
| Disruption | Loss or interference with a structure that had initially developed normally |
| Dysplasia | Abnormal organization of tissue or cells within a structure |
| Sequence | Multiple effects arising through a cascade from an initial problem |
These terms describe developmental relationships. They do not, by themselves, establish a molecular cause or a recurrence risk.
Case 1: A mechanical change after formation
An infant's foot is held in an abnormal position after prolonged intrauterine constraint. The case specifies that the foot initially formed normally and that the later change resulted from mechanical forces. Which developmental term best describes this change?
- Malformation
- Deformation
- Disruption
- Dysplasia
Answer: B. A deformation is an alteration in shape or position caused by mechanical forces after initial formation. A malformation arises during formation; a disruption involves damage to a structure that had initially developed normally; dysplasia concerns abnormal tissue organization. The stated mechanism, rather than the appearance alone, determines the best answer.
Sources: CDC terminology and classification, Appendix C; CDC renal agenesis/hypoplasia discussion.
Case 2: One initiating problem, several consequences
A fetus has bilateral renal agenesis, followed by severe oligohydramnios, pulmonary hypoplasia, and limb contractures. The question asks how the renal finding and its downstream effects relate to one another. Which description best fits?
- Several unrelated malformations with no developmental relationship
- An association in which no causal cascade is established
- A sequence initiated by the renal abnormality
- A dysplasia affecting the organization of one tissue
Answer: C. In this example, the renal abnormality reduces fetal urine contribution to amniotic fluid. The resulting oligohydramnios contributes to the later pulmonary and positional findings. This is a sequence: related consequences follow an initiating abnormality. Calling the pattern a sequence does not establish why the kidneys failed to form or supply a recurrence risk. The initiating malformation and the downstream sequence are descriptions at different levels.
Sources: CDC terminology and classification, Appendix C; CDC renal agenesis/hypoplasia discussion.
Link the mechanism to the next question
After identifying the developmental relationship, ask what the case gives you about etiology, associated findings, and family history. Avoid assigning a recurrence risk from a descriptive term alone. The same visible finding can arise through different mechanisms.
Use EveryGene Academy for additional application. The 101 Must-Know Genetic Conditions flashcards support condition review; use the free pediatric workbook.
Source: CDC Birth Defects Surveillance Toolkit terminology glossary. The examples illustrate definitions rather than provide patient-specific diagnostic rules.
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