Congenital anomalies and dysmorphic newborn assessment — branching viva

Stem

You are reviewing a term newborn on the postnatal ward. The baby is hypotonic, with a flat facial profile and bilateral talipes. The parents have noticed that the baby "looks different." The examiner asks you to defend your assessment, your investigation strategy, and your communication. [1]

Examiner: Describe the three clinical movements that frame your assessment of a dysmorphic newborn. [1]

Strong answer: Recognise the anomaly, cluster the findings into a pattern, and refer for genetics with the right test attached. The first move is always to confirm the baby is stable; only then do I complete the head-to-toe examination, document every major and minor finding, take a three-generation family history, and photograph the features before building a diagnostic ladder. [1]

Examiner: The baby has a single palmar crease, a sandal-gap between the toes, and a flat occiput. What is your leading diagnosis? [3]

Strong answer: The pattern points to Down syndrome (Trisomy 21). No single feature is diagnostic, but hypotonia with a flat facial profile, upslanting palpebral fissures, a single palmar crease, and sandal-gap toes together form the recognisable gestalt. I would confirm with a karyotype, which is the targeted first-line test when the phenotype points to a whole-chromosome aneuploidy. [3]

Examiner: Walk me through your genetic test ladder for a dysmorphic newborn whose pattern does not fit a named syndrome. [2]

Strong answer: I start with the test the pattern points to — karyotype for a clear aneuploidy. When the pattern is unexplained, chromosomal microarray is the first-tier test, because it detects the sub-microscopic copy-number variants a karyotype misses. If the baby is critically ill with a suspected monogenic disorder and the microarray is unrevealing, I escalate to rapid exome or genome sequencing, which shortens time to a molecular diagnosis and can change acute management. [2] [11]

Examiner: Why is microarray preferred over karyotype for multiple anomalies of unknown cause? [2]

Strong answer: Microarray has a higher diagnostic yield for unexplained congenital anomalies because it resolves deletions and duplications at a resolution the karyotype cannot reach. Consensus guidelines established it as a first-tier test for this group. Karyotype still has a role when I suspect a whole-chromosome syndrome, because it shows the structural rearrangement directly. [2]

Examiner: The bilateral talipes are rigid. How does that change your thinking? [9]

Strong answer: Idiopathic clubfoot is usually flexible and responds well to the Ponseti method of serial casting and tenotomy. Rigid, bilateral clubfoot, especially with other anomalies, raises the possibility of a syndromic cause such as arthrogryposis or a neural tube defect. I would still start Ponseti casting, but I would widen the work-up and involve genetics and orthopaedics early. [9]

Examiner: How will you raise this with the parents today? [1]

Strong answer: I would speak with both parents together, in plain language, with an interpreter if needed. I would name what I see, explain that the features suggest a pattern I want to confirm with a blood test, and avoid over-promising or over-alarming before I have a diagnosis. I would give them a single trusted clinician to contact, schedule the follow-up, and document the conversation. Parents remember how the news is broken, so honesty, calm, and time matter. [1]

Examiner: One high-yield fact about minor anomalies? [1]

Strong answer: A single minor anomaly is usually normal, but three or more minor anomalies raises the probability of an underlying syndrome sharply, because they cluster when a developmental field is disrupted. [1]