Vacuolar interface dermatitis

Vacuolar interface dermatitis (VAC, also known as liquefaction degeneration, vacuolar alteration or hydropic degeneration) is a dermatitis with vacuolization at the dermoepidermal junction, with lymphocytic inflammation at the epidermis and dermis.¹

Causes of vacuolar interface dermatitis

Main conditions2	Characteristics	Micrograph	Photograph
Generally/Not otherwise specified	Typical findings, called "vacuolar interface dermatitis":2 Mild inflammatory cell infiltrate along the dermoepidermal junction (black arrow in image) Vacuolization within the basal keratinocytes (white arrow in image) Often necrotic, predominantly basal, individual keratinocytes, manifesting as colloid or Civatte bodies
Acute graft-versus-host-disease	Vacuolar alteration of various severity, from focal or diffuse vacuolation of the basal keratinocytes (grade I), to separation at the dermoepidermal junction (grade III) Involvement of the hair follicle2 Rarely eosinophils2
Allergic drug reaction	Rarely involvement of hair follicles.2 Frequently eosinophils2
Lichen sclerosus	Hyperkeratosis, atrophic epidermis, sclerosis of dermis and dermal lymphocytes.3
Erythema multiforme
Lupus erythematosis	Typical findings in systemic lupus erythematosus:4 Fibrinoid necrosis at the dermoepidermal junction Liquefactive degeneration and atrophy of the epidermis Mucin deposition in the reticular dermis Edema, small hemorrhages Mild and mainly lymphocytic infiltrate in the upper dermis Fibrinoid material in the dermis around capillary blood vessels, on collagen and in the interstitium In non-bullous cases, perivascular and interstitial neutrophils are sometimes present in the upper dermis, with damage to blood vessels

An interface dermatitis with vacuolar alteration, not otherwise specified, may be caused by viral exanthems, phototoxic dermatitis, acute radiation dermatitis, erythema dyschromicum perstans, lupus erythematosus and dermatomyositis.²