| Disease/Condition Group | Specific Disease/Condition | Key Specific Features |
|---|---|---|
| Inflammatory & Degenerative Dermatoses | ||
| Eczema (General term) | Morphology: (Acute) Erythema, papules, vesicles, oozing, crusting. (Chronic) Lichenification (thickened skin with accentuated skin lines), scaling, fissuring, xerosis (dryness). Symptoms: Pruritus (itching) is a hallmark. | |
| Atopic Dermatitis | Morphology: Ill-defined erythematous patches, papules, vesicles (acute); lichenification, scaling (chronic). Distribution: (Infants) Face, scalp, extensor surfaces. (Children/Adults) Flexural areas (antecubital/popliteal fossae), neck, wrists, ankles. Symptoms: Intense pruritus (“the itch that rashes”). Associated: Personal/family history of atopy (asthma, allergic rhinitis), xerosis, Dennie-Morgan lines. | |
| Contact Dermatitis | Morphology: Erythema, edema, vesicles, bullae (acute allergic/strong irritant); scaling, lichenification, fissures (chronic). Often geometric or linear, corresponding to exposure. Distribution: Site of contact with allergen (e.g., nickel, poison ivy) or irritant (e.g., soaps, solvents). Symptoms: Pruritus (allergic > irritant), burning/stinging (irritant > allergic). Patch testing for allergens. | |
| Drug Eruption (Morbilliform is most common) | Morphology: Symmetrical, erythematous macules and papules (“morbilliform” or “maculopapular”), may become confluent. Distribution: Trunk, spreads peripherally. Mucous membranes usually spared. Symptoms: Mild to moderate pruritus. Onset: Typically 7-14 days after starting new drug. | |
| Psoriasis (Plaque type) | Morphology: Well-demarcated, erythematous plaques with thick, silvery-white scales. Distribution: Extensor surfaces (elbows, knees), scalp, lumbosacral area, gluteal cleft, umbilicus. Nails: pitting, onycholysis, oil spots. Symptoms: Often pruritic, can be painful. Signs: Auspitz sign (pinpoint bleeding on scale removal), Koebner phenomenon (lesions at site of trauma). | |
| Pityriasis Rosea | Morphology: Herald patch (single, larger, oval, erythematous, slightly raised lesion with fine scale) followed by generalized eruption of smaller, oval, pink-tan macules/papules with fine collarette of scale. Distribution: “Christmas tree” pattern on trunk and proximal extremities, along skin cleavage lines. Spares face, scalp, palms, soles. Symptoms: Mild to moderate pruritus. Self-limiting. | |
| Lichen Planus | Morphology: 4 P’s: Pruritic, Purple (violaceous), Polygonal, Papules/Plaques. Wickham’s striae (fine white lines on surface of lesions and oral mucosa). Distribution: Flexor wrists, forearms, ankles, mucous membranes (oral - lacy white pattern, genital), nails (pterygium, thinning). Symptoms: Intense pruritus. Koebner phenomenon. | |
| Acne Vulgaris / Acne | Morphology: Comedones (open/blackheads, closed/whiteheads), inflammatory papules, pustules, nodules, cysts. Seborrhea (oily skin). Distribution: Face, chest, back, shoulders (areas rich in sebaceous glands). Pathophysiology: Follicular hyperkeratinization, increased sebum, Cutibacterium acnes, inflammation. | |
| Vesiculobullous Skin Diseases | Generally characterized by vesicles (small fluid-filled blisters <1cm) and bullae (large fluid-filled blisters >1cm). Nikolsky sign (dislodging of epidermis by lateral pressure) can be positive in some (e.g., Pemphigus). | |
| Vitiligo | Morphology: Well-demarcated, depigmented (chalky white) macules and patches. Hair in affected areas may also be white (leukotrichia). Distribution: Periorificial, acral, sites of trauma (Koebner phenomenon). Signs: Wood’s lamp examination accentuates depigmentation. | |
| Dermatoses in Pregnancy | PUPPP (Pruritic Urticarial Papules and Plaques of Pregnancy): Erythematous, urticarial papules and plaques, often starting in striae; abdomen (sparing umbilicus), thighs. Intense pruritus. 3rd trimester. Pemphigoid Gestationis: Urticarial plaques/papules evolving to tense vesicles/bullae; periumbilical, abdomen, extremities. Severe pruritus. Autoimmune. | |
| Urticaria (Hives) | Morphology: Wheals: transient (individual lesions <24h), edematous, erythematous or pale, well-circumscribed plaques. Distribution: Anywhere on the body. Symptoms: Intense pruritus, sometimes burning. Angioedema may co-exist. Darier’s sign (if mastocytosis). | |
| Infectious Skin Diseases | ||
| Skin Bacterial Infections | Impetigo (Non-bullous): “Honey-colored” crusts on erythematous base; face, extremities. Cellulitis: Spreading erythema, warmth, swelling, tenderness, ill-defined borders; often lower legs. Folliculitis: Erythematous papules/pustules centered on hair follicles. | |
| Viral Skin Infections | Herpes Simplex (HSV): Grouped vesicles on erythematous base, then erosions/crusts; orolabial, genital. Recurrent, prodrome of tingling/pain. Varicella-Zoster (Shingles): Dermatomal eruption of grouped vesicles on erythematous base; unilateral, pain. Molluscum Contagiosum: Pearly, dome-shaped papules with central umbilication. | |
| Fungal Infections | Tinea Corporis (Ringworm): Annular (ring-shaped) erythematous plaques with raised, scaly borders and central clearing. Tinea Versicolor: Hypo- or hyperpigmented or mildly erythematous macules/patches with fine scale; trunk. “Spaghetti and meatballs” on KOH. Candidiasis (Cutaneous): Beefy red, moist plaques, often with satellite papules/pustules; intertriginous areas. | |
| Parasitic Infestations | Scabies: Intense nocturnal pruritus; burrows, papules, vesicles; finger webs, wrists, axillae, genitals. Pediculosis (Lice): Pruritus; nits (eggs) on hair shafts (capitis/pubis), lice may be seen; scalp, pubic area, body (seams of clothing). | |
| Benign & Malignant Growths | ||
| Common Benign Skin Growths | Seborrheic Keratosis: Well-demarcated, “stuck-on” appearance, waxy/verrucous surface, variable pigmentation. Cherry Angioma: Bright red to violaceous, dome-shaped papules of dilated capillaries. Dermatofibroma: Firm, pigmented (tan-brown) papule/nodule; “dimple sign” on lateral compression. | |
| Common Skin Malignancies | Basal Cell Carcinoma (BCC): Pearly papule/nodule with telangiectasias, rolled border, central ulceration (rodent ulcer). Slow growing. Squamous Cell Carcinoma (SCC): Erythematous, indurated, scaly/crusted papule/plaque/nodule; may ulcerate or be hyperkeratotic (cutaneous horn). Melanoma: ABCDEs: Asymmetry, irregular Border, Color variegation, Diameter >6mm, Evolving/Elevation. High metastatic potential. | |
| Vascular Malformations (Example) | Port-Wine Stain (Nevus Flammeus): Flat, pink-red to purple patches present at birth. Do not involute. May thicken with age. If V1 distribution, consider Sturge-Weber syndrome. | |
| Disorders of Appendages | ||
| Alopecia | Androgenetic Alopecia (Male/Female Pattern Baldness): (Male) Bitemporal recession, vertex thinning. (Female) Diffuse thinning over crown, preservation of frontal hairline. Alopecia Areata: Well-demarcated, round/oval patches of non-scarring hair loss; “exclamation point” hairs. Autoimmune. Telogen Effluvium: Diffuse, non-scarring hair shedding after a stressor; positive hair pull test. |