Epidermolysis bullosa and inherited blistering disorders — viva

Opening (2 minutes)

The candidate should recognise the picture of inherited epidermolysis bullosa presenting at birth: erosions and blisters that track friction and handling, periorificial involvement, a hoarse cry, and poor feeding in a baby with no family history. The diagnosis is clinical but provisional, and a strong candidate commits to inherited EB, narrows the subtype, identifies the immediate airway and sepsis threats, and plans the atraumatic handling and the diagnostic biopsy in parallel rather than waiting for one to finish before starting the other. [1]

Branch 1 — classification and pathophysiology

Examiner: "Which subtype do you suspect and what is the underlying defect?" The expected answer identifies junctional EB generalised severe, formerly Herlitz, because of the periorificial granulation tissue, the hoarse cry that signals laryngeal granulation tissue, and the severe blistering at birth. The split lies in the lamina lucida of the basement membrane, and the defective proteins are laminin-332, encoded by LAMA3, LAMB3 or LAMC2, and type XVII collagen, encoded by COL17A1, which together fail to anchor the basal keratinocyte to the basement membrane. [5]

A candidate who distinguishes the four types by cleavage level demonstrates mastery: EB simplex splits within the basal keratinocytes and is usually autosomal dominant with keratin five and fourteen defects; junctional EB splits in the lamina lucida and is autosomal recessive; dystrophic EB splits beneath the lamina densa from COL7A1 anchoring-fibril failure and is the subtype that scars and carries the squamous cell carcinoma risk; Kindler EB splits at variable levels with poikiloderma. The absence of a family history fits the autosomal recessive junctional pattern, and the candidate should state the one-in-four sibling recurrence that follows. [1]

Branch 2 — diagnosis and the biopsy

Examiner: "How do you confirm the diagnosis?" The biopsy technique is the discriminator between a strong and a weak candidate, because an old lesion gives a false cleavage level. The clinician induces a fresh blister by gentle rotation or rubbing of unaffected skin, biopsies across the edge of the new lesion within twenty-four hours, and sends it in Michel's medium for immunofluorescence antigen mapping and in glutaraldehyde for electron microscopy. [1]

Immunofluorescence antigen mapping is the first-line test: a panel of antibodies against the key structural proteins localises the cleavage level and reveals whether the protein is reduced or absent, and electron microscopy adds ultrastructural detail such as anchoring-fibril counts. Genetic testing with an EB gene panel then confirms the responsible mutation, anchors inheritance counselling, and supports prenatal and preimplantation diagnosis in future pregnancies. The candidate should explain why a biopsy on an old, re-epithelialised blister can mislead the cleavage level, because that single principle protects the diagnosis. [5]

Branch 3 — management and the airway threat

Examiner: "Lay out your immediate and ongoing management." Immediate care protects the airway, because the hoarse cry may herald laryngeal obstruction from granulation tissue; the candidate arranges urgent paediatric and ear-nose-throat assessment, airway protection if distressed, and transfer to a specialist EB centre. Sepsis is the second immediate threat, with new spreading erythema or fever warranting intravenous access obtained without adhesive tape and empiric antibiotic therapy directed at skin organisms. [11]

Definitive care rests on atraumatic handling as its foundation: no adhesive tape, lift rather than slide, secure lines with soft silicone or nothing, and dress each wound with a non-adherent silicone contact layer, an absorbent secondary layer and a soft conforming bandage. Pain is treated before every dressing change, nutrition is supported with nasogastric or gastrostomy feeding when oral intake fails, and the family receives honest counselling and a named specialist contact. The candidate should close by naming the multidisciplinary team and the structured transition that governs lifelong care, and by acknowledging the guarded prognosis of junctional EB generalised severe. [7]

Closing (1 minute)

Summarise the plan: recognise junctional EB generalised severe clinically, protect the airway and treat sepsis, plan the induced-blister biopsy read by immunofluorescence mapping and confirmed genetically, and build lifelong care on atraumatic handling, non-adherent dressings, pain control, nutrition and a multidisciplinary team, with honest family counselling and structured transition throughout. [1]