A 6-month-old infant presents with large areas of eroded skin from birth, with blistering on minimal friction. EM shows absent hemidesmosomes and no anchoring fibrils. The gene mutation is in:

• A COL7A1 encoding type VII collagen ✓
• B KRT5/KRT14 encoding keratin 5/14
• C LAMB3 encoding laminin-332 beta-3 chain
• D ITGB4 encoding integrin beta-4

Explanation

The absence of anchoring fibrils on electron microscopy places this in the sub-lamina densa zone, consistent with dystrophic epidermolysis bullosa (DEB). DEB is caused by mutations in COL7A1 (type VII collagen gene), which encodes the major component of anchoring fibrils at the sub-lamina densa. Absence of anchoring fibrils = dystrophic EB. KRT5/KRT14 mutations cause simplex EB (intraepidermal blistering, EM shows disrupted tonofilaments). LAMB3 mutations cause junctional EB Herlitz type (absent hemidesmosomes, blistering in lamina lucida). ITGB4 mutations also cause junctional EB with absent hemidesmosomes but also pyloric atresia.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.