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Lamina densa (type IV collagen basement membrane)

Adhesion & dermo-epidermal junction · Type IV collagen Nidogen, perlecan

The basement membrane proper: a type IV collagen network cross-linked with nidogen and the heparan sulphate proteoglycan perlecan, continuous with the basement membranes that sheath the appendages and dermal vessels.

Traced from the start

  1. Stratum basale (germinativum)
  2. Lamina densa (type IV collagen basement membrane)

Detail

Composition
Type IV collagen scaffold with laminins, nidogen and perlecan
Continuity
Runs without interruption around hair follicles, sweat ducts and dermal capillaries, which is why appendageal epithelium survives when the surface epidermis is destroyed
Barrier role
Restricts cell traffic; invasion through it is the histological definition of an invasive rather than in-situ carcinoma

When it goes wrong

Keratinocyte apoptosis driven by granulysin and Fas-FasL in Stevens-Johnson syndrome and toxic epidermal necrolysis

Full-thickness epidermal necrosis detaching at the dermo-epidermal junction with positive Nikolsky and mucosal erosions; commonest triggers are allopurinol, carbamazepine, lamotrigine, sulfonamides and nevirapine, and SCORTEN predicts mortality

Breach of the lamina densa by a squamous or basal cell carcinoma

The lesion becomes invasive rather than in situ (Bowen disease), acquiring metastatic potential and requiring wider excision

Practise this structure

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