Perplexing presentations and diagnostic uncertainty — branching viva

Opening

Examiner: A seven-year-old boy is referred to you after two years of recurrent vomiting, lethargy and fainting episodes. He has been seen at four hospitals, has had repeated blood tests, two endoscopies and a CT, and is on two medications. His parents give different histories. His school attendance is under 30%. His mother is asking you to insert a feeding tube. How do you frame this? ^[5]

Candidate: I would frame this as a perplexing presentation — a clinical situation in which the reported symptoms, signs and findings are not adequately explained by any recognised disease, but in which there is not yet objective evidence of harm or falsification. The RCPCH describes this as the middle of a three-level escalation: alerting signs raise concern, the perplexing presentation triggers structured assessment, and fabricated or induced illness is the child-protection end. My job is to hold three limbs in parallel — a genuine rare or complex organic disease, a medically unexplained or functional disorder, and a safeguarding concern — and to resist the two opposite errors: dismissing genuine disease, or jumping to an abuse label without evidence. I would not agree to a feeding tube today. ^[5]

Branch 1 — the balanced differential

Examiner: Walk me through how you build the three-limb differential. ^[5]

Candidate: For the organic limb, I look for reproducibility on independent observation, objective findings between episodes, a trajectory consistent with a known disease, and a response to disease-directed treatment. For the functional or somatising limb, I look for a consistent functional pattern, a personal or family history of somatisation or anxiety, normal objective findings throughout, and a positive response to a functional explanation and rehabilitation. For the safeguarding limb, I look for symptoms present only in one caregiver's presence, discrepancies across records from different centres, objective absence on separate observation, and escalating, unjustified intervention causing iatrogenic harm. None of these limbs is mutually exclusive — a child may have a real, mild disease overlaid by exaggeration, or a somatising adolescent who is also being harmed. ^{[5] [3]}