Interstitial lung disease in children — structured oral (viva)

Branch 1 — Framing the problem

Examiner: "This baby has been breathing fast for months. What is the single concept that organises your thinking?" Candidate: The concept is the chILD syndrome. This is chronic, diffuse lung disease rather than a run of acute infections, and he meets the syndrome because he has respiratory symptoms, respiratory signs with tachypnoea and diffuse crackles, hypoxaemia at rest and with feeds, and diffuse change on imaging. Once I have excluded the common causes, that combination means children's interstitial lung disease until proven otherwise, and it demands a structured diffuse-lung-disease work-up rather than another course of antibiotics. [1]

Branch 2 — Classification and differential

Examiner: "You suspect chILD. How do you narrow it down at his age?" Candidate: I narrow it by age, because chILD splits into an infancy-predominant group and an older-child group. In an infant the leading possibilities are the genetic surfactant dysfunction disorders, the developmental and growth abnormalities, and the specific conditions of unknown cause, above all neuroendocrine cell hyperplasia of infancy. Given that he was well at birth and became symptomatic after the first weeks, is thriving poorly, and has persistent tachypnoea, I would put neuroendocrine cell hyperplasia of infancy and a surfactant protein C disorder near the top. [1] [3]

Examiner: "Why does the timing of onset matter?" Candidate: Timing separates the lethal from the chronic. Severe, progressive respiratory failure from birth in a term baby suggests surfactant protein B or ABCA3 deficiency, which are often fatal. Onset after the first weeks of life in a previously well infant, running a chronic course, fits neuroendocrine cell hyperplasia of infancy or surfactant protein C disease, which behave much more benignly. [3] [2]

Branch 3 — Investigation

Examiner: "How will you investigate him?" Candidate: I would work on two tracks. First I exclude the common causes with a sweat test and cystic fibrosis genetics, an immune screen, a swallow and aspiration assessment, and an echocardiogram to exclude congenital heart disease and to look for pulmonary hypertension. Then I characterise the diffuse disease with a high-resolution CT of the chest, which is far more useful than the plain film and can be near-diagnostic for neuroendocrine cell hyperplasia of infancy when it shows right-middle-lobe and lingular ground-glass with air trapping. I would send an early surfactant-gene panel, because a positive result confirms the diagnosis and can avoid a lung biopsy. [4] [2]

Examiner: "When would you proceed to lung biopsy?" Candidate: Only when imaging and genetics leave the diagnosis unresolved and the result will change management. It should be a video-assisted thoracoscopic biopsy at a centre with paediatric ILD pathology expertise, using the specific stains the field has standardised, including neuroendocrine cell immunostaining. If the HRCT is classic for neuroendocrine cell hyperplasia of infancy, I would avoid a biopsy altogether. [2] [1]

Branch 4 — Management and prognosis

Examiner: "Assume the HRCT is classic for neuroendocrine cell hyperplasia of infancy. How do you manage him, and what do you tell the family?" Candidate: Neuroendocrine cell hyperplasia of infancy is managed supportively, without immunosuppression. I would optimise oxygenation with supplemental oxygen to correct the hypoxaemia and protect growth and the pulmonary circulation, support nutrition aggressively, complete immunisations including influenza, give respiratory syncytial virus prophylaxis if eligible, and ensure a smoke-free environment, all coordinated through a specialist chILD centre. I would reassure the family that this condition, though it looks alarming, generally improves gradually over years, and that corticosteroids are neither needed nor helpful here — which contrasts sharply with the inflammatory chILD disorders and the lethal surfactant deficiencies. [1] [4]