Lamellar ichthyosis is caused by a defect in which enzyme, and its histological hallmark is:
- A Transglutaminase-1 (TGM1) mutation; massive compact orthokeratotic hyperkeratosis with thickened granular layer ✓
- B Steroid sulphatase deficiency; perinuclear vacuolization of keratinocytes
- C ABCA12 mutation; electron-lucent vacuoles in the stratum corneum
- D Loricrin mutation; intranuclear pseudo-inclusions of loricrin in granular layer cells
Explanation
Lamellar ichthyosis (LI), the most common form of autosomal recessive congenital ichthyosis (ARCI), is most commonly caused by mutations in TGM1 (transglutaminase-1), the enzyme responsible for cross-linking of cornified envelope proteins during terminal keratinocyte differentiation. Histology shows massive orthokeratotic hyperkeratosis with a normal or thickened granular layer (unlike X-linked ichthyosis which has steroid sulphatase deficiency and normal/reduced granular layer). ABCA12 mutations cause Harlequin ichthyosis. Loricrin mutations cause Vohwinkel syndrome variant.
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.