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Background

Nowhere in pathology is the accurate correlation between the clinical appearance of a patient's lesions and the histologic appearance of the microscopic slide more important than the diagnosis of skin rashes.  Many skin rashes have similar histologic appearances, in spite of the very different clinical appearance on the patient.  Conversely, similar clinical lesions may have vastly different histologic appearances. 

Acne Vulgaris
Acral Pseudolymphomatous Angiokeratoma of Children (APACHE)
Acral persistent papular mucinosis
Acrodermatitis Enteropathica
Alopecia mucinosa (Follicular mucinosis)
Anti-p200 Pemphigoid
Anti-p450 Pemphigoid
Argyria
Arthropod Bites (Bug Bite)
Atopic Dermatitis
Axillary Granular Parakeratosis
Brachioradial Pruritis
Bullous pemphigoid
Calciphylaxis
Cellulitis
Chilblains
Cicatricial pemphigoid
Clear Cell Papulosis
Contact Dermatitis
Cryoglobulinemia
Cutaneous mucinosis of infancy
Cutaneous myxoma
Darier's Disease (Keratosis follicularis)
Deep lamina lucida pemphigoid (Anti-p105kd bullous dermatosis)
Degos Disease (Malignant Atrophic Papulosis)
Dermal disorders (Disorders of collagen, elastic fibers, mucin, scar, cicatrix)
Dermal mucinosis
Dermatitis herpetiformis
Dermatomyositis
Dermatophyte (Tinea, Ringworm)
Digital mucous cyst
Drug Reactions
Eczema
Epidermolysis Bullosa
Epidermolysis bullosa acquisita
Erythema Elevatum Diutinum
Erythema multiforme
Erythrasma
Erythroderma
Erythromelanosis follicularis et colli
Favre-Racouchot Disease (Nodular Elastosis with Cysts and Comedones)
Fixed drug eruption
Focal mucinosis
Gangrene
Gianotti-Crosti Syndrome
Graft-versus-host disease
Granuloma annulare
Grover's Disease (Transient Acantholytic Dyskeratosis)
Hailey-Hailey Disease (Benign Familial Pemphigus)
Hand Foot Mouth Disease
Herpes gestationis (Pemphigoid gestationis)
Hidradenitis Suppurativa
Hydroa Vacciniforme
Ichthyosis
Incontinentia pigmenti
Interstitial Granulomatous Dermatitis
Jessner's Lymphocytic Infiltrate of the Skin
Kawasaki's syndrome
Lichen nitidus
Lichen planus
Lichen planus-like keratosis
Lichen striatus
Lichenoid Dermatoses and tissue reactions
Linear IgA disease
Lupus erythematosus (SLE, DLE, SCLE)
Mucocele
Mucopolysaccharidoses
Myxedema, Generalized
Myxedema, Pretibial
Necrobiosis lipoidica
Necrobiotic xanthogranuloma
Necrolytic Migratory Erythema
Neonatal Cephalic Pustulosis
Neutrophilic Eccrine Hidradenitis
Nevus mucinosis
Onychomycosis
Papular mucinosis (Lichen myxedematosus)
Paraneoplastic Pemphigus
Pemphigus erythematosus
Pemphigus foliaceus
Pemphigus vegetans
Pemphigus vulgaris
Perniosis
Pigmented Purpuric Dermatoses
Pityriasis Lichenoides et Varioliformis Acuta (PLEVA, Mucha-Habermann Disease)
Pityriasis Lichenoides Chronica
Poikilodermas
Polymorphous Light Eruption
Porokeratosis
Porphyria
Pseudoporphyria
Psoriasis
Pustular Psoriasis
Pyoderma gangrenosum
Reactive angioendotheliomatosis
Reticular erythematous mucinosis
Rosacea
Scleredema
Scleromyxedema
Scurvy
Sneddon-Wilkinson Dermatosis (Subcornal Pustular Dermatosis)
Sweet's Syndrome (Acute Febrile Neutrophilic Dermatosis)
Tinea versicolor (Pityriasis versicolor)
Tumor Necrosis Factor Receptor-Associated Periodic Syndrome (TRAPS)
Urticaria
Vasculitis
Xanthoma

Cicatrix-Scar.

Diffuse/Nodular Dermatitis

Dermal Histologic Pattern	Diagnosis
Lymphocytes	Pseudolymphoma Lymphoma
Neutrophils	Sweet's syndrome Inflammatory bowel disease Rheumatoid neutrophilic dermatitis Pyoderma gangrenosum Follicular cyst, ruptured Granuloma faciale Erythema elevatum diutinum
Neutrophils and eosinophils	Granuloma faciale Erythema elevatum diutinum
Plasma cells	Rhinoscleroma Leishmaniasis Syphilis, primary Chancroid Granuloma inguinale Lymphogranuloma venereum Pseudolymphoma Granuloma faciale Erythema elevatum diutinum
Mast cells	Urticaria pigmentosa, nodular
Abnormal leukocytes	Extramedullary hematopoisis Pseudolymphoma Lymphoma
Histiocytes	Botryomycosis Blastomycosis-like pyoderma Rhinoscleroma Actinomycosis Nocardiosis Streptomycosis Cryptoococcosis Histoplasmosis Blastomycosis Paracoccidioidomycosis Chromomycosis Coccidioidomycosis Sporotrichosis Rhinosporidiosis Kerion Candida granuloma Eumycetoma Phycomycosis Alternariosis Dermatophytosis (Majocchi's granuloma) Protothecosis Amebiasis Acne congobata/acne keloidalis Hidradenitis suppurativa Dissecting cellulitis of the scalp Pilondial sinus Follicular cyst, ruptured Halogenoderma Tuberculosis cutis verrucosa Atypical mycobaterial infections Leprosy Dermatofibroma, early Langerhans' cell histiocytosis Granulomatous slack skin
Histiocytes and Lipophages	Xanthelasma Xanthoma Xanthoma disseminatum Verruciform xanthoma Xanthogranuloma Generalized eruptive histiocytoma Malacoplakia Silicone granuloma Paraffinoma

Interface Dermatitis

Interstitial-Refers to the location of inflammatory cells between vessels within the dermis. 

Lichenoid-Epidermal basal cell damage with vacuolar degenerative changes associated with inflammatory cells.

Panniculitis-Inflammation of the fat.

Spongiosis-Refers to edema or swelling between the epithelial cells.  It is the histologic correlation of eczema.

Subepidermal Vesicular Dermatitis

Dermal Histologic Pattern	Diagnosis
Little or no infiltrate	Epidermolysis bullosa, junctional, dermolytic, acquired Bart syndrome Hypoxemia plus pressure Acute burn Erythema multiforme, severe
Lymphocytes	Erythema multiforme LSEA Mucha-Habermann disease Lichen planus, bullous Pseudolymphoma Lymphoma
Eosinophils	Bullous pemphigoid Herpes gestationis Acquired EB Arthropod
Neutrophils	Dermatitis herpetiformis DH-like drug eruption Linear IgA disease EBA SLE Leukocytoclastic vasculitis Septic vasculitis Pyoderma gangrenosum Cellulitis Bullous pemphigoid Herpes gestationis Cicatricial pemphigoid
Eosinophils and neutrophils	Dermatitis herpetiformis DH-like drug eruption Linear IgA disease EBA Bullous pemphigoid Herpes gestationis
Mast Cells	Urticaria pigmentosa

Superficial Perivascular Dermatitis-Refers to the location of inflammatory cells around the superficial portions of the dermal blood vessels.

Epidermal Changes	Dermal Histologic Pattern	Diagnosis
No epidermal changes
	Superficial Perivascular Dermatitis
	Lymphocytes predominate	Tinea versicolor Dermatophytosis Erythrasma Pitted keratolysis Vitiligo Schamberg's disease Viral exanthems Drug eruption (one type) Urticaria, late Erythema figuratum, superficial
	Superficial perivascular and interstitial dermatitis
	Lymphocytes predominate	Schamberg's disease Pruritic urticarial papules and plaques of pregnancy (PUPPP)
	Neutrophils predominate	Dermatitis herpetiformis Linear IgA dermatosis Dermatitis herpetiformis-like drug eruptions Acute discoid lupus erythematosus/SLE Leukocytoclastic vasculitis Erythema marginatum
	Eosinophils predominate	Bullous pemphigoid/Herpes gestationis, urticarial Pemphigus vulgaris, urticarial Arthropod PUPPP
	Neutrophils and eosinophils predominate	Urticaria
	Melanophages predominate	Postinflammatory pigmentary alteration Macular amyloidosis
	Siderophages predominate	Stasis
	Macrophages with features of melanophages and siderophages predominate	Minocycline-induced eruption
	Mast cells predominate	Urticaria pigmentosa Brachioradial pruritis
Ballooning changes	Lymphocytes predominate-ballooning mostly	Herpesvirus infection
	Lymphocytes predominate	Measles
	Psoriasiform and lymphocytes predominate	Orf Milker's nodule
Spongiosis
	Lymphocytes predominate	Allergic contact dermatitis Nummular dermatitis Dyshidrotic dermatitis Id reaction Photoallergic dermatitis, early Dermatophytosis Miliaria rubra Gianotti-Crosti syndrome Pityriasis rosea Erythema annulare centrifugum Seborrheic dermatitis Lichen striatus Pityriasis alba Mycosis fungoides, macule/patch
	Eosinophils predominate	PUPPP Allergic contact dermatitis Nummular dermatitis Dyshidrotic dermatitis Id reaction Bullous pemphigoid Herpes gestationis Pemphigus vulgaris, urticarial Incontinentia pigmenti Toxic erythema of newborn Arthropod assault
Spongiotic Psoriasiform	Lymphocytes predominate	Allergic contact dermatitis Nummular dermatitis Dyshidrotic dermatitis Id reaction Seborrheic dermatitis Nonbullous congenital ichthyosiform erythroderma Lichen striatus
Spongiotic Lichenoid	Lymphocytes predominate	Lichen striatus Bullous pemphigoid Herpes gestationis, urticarial
		Mycosis fungoides
Spongiotic Psoriasiform Lichenoid	Lymphocytes predominate	Lichen striatus Bullous pemphigoid Herpes gestationis, urticarial Mycosis fungoides
Psoriasiform only
	Lymphocytes predominate	Psoriasis Allergic contact dermatitis Nummular dermatitis Dyshidrotic dermatitis Pityriasis rubra pilaris Seborrheic dermatitis Dermatophytosis Candidiasis Lichen simplex chronicus Prurigo nodularis Acanthoma fissuratum Pressure papule from prosthesis Surfer's nodules Chondrodermatitis nodularis helicis
Psoriasiform Lichenoid	Lymphocytes predominate	Lichen striatus Mycosis fungoides Inflammatory linear verrucous epidermal nevus
	Histiocytes and plasma cells predominate	Syphillis, secondary

Superficial and Deep-Refers to the location of inflammatory cells around the superficial or deeper portions of the dermal blood vessels.

Epidermal Changes	Dermal Histologic Pattern	Diagnosis
No epidermal changes
	Perivascular Dermatitis
	Lymphocytes predominate	Polymorphous light eruption, early Erythema figuratum Erythema chronicum migrans Pernio Erythema nodosum PMLE DLE, tumid CLL B-cell lymphoma
	Eosinophils prominent	Arthropod insult
	Plasma cells prominent	Erythema chronicum migrans Scleroderma
	Histiocytes and lymphocytes prominent	Leprosy, indeterminate
	Perivascular and Interstitial Dermatitis
	Neutrophils	Suppurative folliculitis, periphery Neutrophilic eccrine hidradenitis Flea bite Cellulitis Erythropoietic protoporphyria
	Eosinophils	Arthropod Erythema chronicum migrans Well's syndrome
	Eosinophils and neutrophils	Urticaria
	Plasma cells	Erythema chronicum migrans
	Neutrophils, eosinophils, plasma cells	Scleroderma, early
	Histiocytes predominate	Granuloma annulare Necrobiosis lipoidica Interstitial granulomatous dermatitis with arthritis Mycosis fungoides, granulomatous
Ballooning Epidermal Changes
	Lymphocytes predominate
	Ballooning only	Hyroa aestivale/Hydroa vacciniforme
	Interface	Herpesvirus Fixed drug eruption
	Spongiosis	Toxic shock syndrome
Spongiotic
	Lymphocytes	Photoallergic dermatitis Early PMLE
	Eosinophils	Arthropod Bullous pemphigoid Herpes gestationis, urticarial
	Psoriasiform lymphocytes	Photoallergic dermatitis Mycosis fungoides, plaque
	Lichenoid lymphocytes	Fixed drug eruption Dermatophytosis Acrodermatitis chronica atrophicans Mycosis fungoides, plaque
	Psoriasiform lichenoid lymphocytes	Mycosis fungoides, plaque
Psoriasiform
	Psoriasiform lymphocytes	Dermatophytosis Norwegian scabies Persistent light eruption Actinic reticuloid Pityriasis rosea, herald patch
	Lichenoid lymphocytes	Lichen striatus Mycosis fungoides, plaque
	Lichenoid histiocytes, plasma cells	Syphilis, secondary

Adapted from Algorithms for Histologic Diagnosis of Inflammatory Skin Diseases. Second Edition. Williams and Wilkins. 1997

Last Updated 6/6/2002

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