Inflammatory skin disorders

Inflammatory skin disorders are a significant part of dermatopathology. They lead to trepidation among pathologists that don't see lots of skin.

Spongiotic dermatitides

DDx:

• Atopic dermatitis.
• Contact dermatitis.
• Stasis dermatitis.
• Seborrheic dermatitis.
• Nummular dermatitis.
• Spongiotic drug eruption.

Psoriasiform dermatitides

Regular psoriasiform dermatitis

DDx:

• Psoriasis vulgaris.
• Dermatophyte infection.
• Pityriasis rubra pilaris.

Irregular psoriasiform dermatitis

• Lichen simplex chronicus.

Interface dermatitides

Vacuolar interface dermatitides

DDx:

• Erythema multiforme.
• Lichen sclerosus.
• Fixed drug eruption.

Others:

• Graft versus host disease.
• Dermatomyositis.
• Systemic lupus erythematosus.
• Morbillifrom viral exanthem.

Lichenoid interface dermatitides

DDx:

• Lichen planus
• Mycosis fungoides.
• Discoid lupus erythematosus.
• Lichenoid drug eruption.
• Fixed drug eruption.

Bullous disease

Subcorneal bullous disorders

DDx with acantholysis:

• Pemphigus foliaceous.
• Bullous impetigo.
• Staphylococcual scaled skin syndrome.

DDx without acantholysis:DDx:

• Subcorneal pustular demratosis (Sneddon-Wilkinson disease)
• Pustular psoriasis.
• Pustular drug eruption (acute generalized exanthematous pustulosis).

Suprabasilar bullous disorders

DDx:

• Pemphigus vulgaris.
• Hailey-Hailey disease (benign familial pemphigus).
• Darier disease.
• Grover disease (transient acantholytic dermatosis).

Subepidermal bullous disorders

DDx:

• Bullous pemphigoid.
• Cicatricial pemphigoid.
• Porphyria cutanea tarda.
• Epidermolysis bullosa acquista.
• Dermatitis herpetiformsis.
• Linear IgA disease.

Others:

• Insect bite.
• Coma blister.
• Bullous systemic lupus erythematosus.

Perivascular inflammation

Lymphocytes

Lymphocytes (tightly cuffed):

• Infections.
• Medications.
• Malignancy.
• Vitiligo (with absent melanocytes).
• Scleroderma/morphea.

Lymphocytes & plasma cells +/-eosinophils:

• Erythema chronicum migrans (Lyme disease).

Lymphocytes (not tightly cuffed):

• Viral exanthems.
• Drug eruptions.

Lymphocytes & eosinophils:

• Drug reaction.
• Insect bite.
• Dermatophyte infection.

Neutrophils

DDx:

• Cellulitis.
• Neutrophilic eccrine hidradenitis (idiopathic palmar-plantar hidradenitis)

With eosinophils:

• Urticaria.

Eosinophils

DDx:

• Hypersensitivity reaction/drug reaction.
• Insect bite.
• Bullous pemphigoid, urticarial.

Mast cells

• Mastocytosis.

Vasculitis

Main article: Vasculitides

See also

• Dermatopathology.
• Non-malignant skin disease.