Essential Dermatology: Skin Lesion Definitions and Chronic Conditions

Posted on Nov 25, 2025 in Environmental Biology

Common Chronic Skin Conditions

• Xerosis (Dry Skin)
• Pruritus (Itching)

Primary Skin Lesions

Types of Primary Lesions

1. Macule
2. Patch
3. Papule
4. Plaque
5. Nodule
6. Tumor
7. Wheal
8. Vesicle
9. Bulla
10. Pustule

Definitions of Primary Lesions

• Macule

  Small, flat, non-palpable lesion, **≤ 1 cm** in diameter.

• Patch

  A large macule, flat, non-palpable lesion, **> 1 cm** in diameter.

• Papule

  Small, elevated, solid lesion, **≤ 0.5 cm** in diameter, with no visible fluid.

• Plaque

  Larger, elevated, solid lesion, **> 0.5 cm** in diameter. Can be a coalescence of papules.

• Nodule

  A solid, elevated lesion, **0.5–2 cm** in diameter, deeper and firmer than a papule.

• Tumor

  A large nodule, **> 2 cm** in diameter, typically solid (no fluid).

• Wheal (Hives)

  Localized skin edema; irregular, transient, and superficial. Variable size. Contains no fluid or blood.

• Vesicle

  Small, elevated lesion, **≤ 0.5 cm** in diameter, filled with serous fluid.

• Bulla

  A large vesicle, **> 0.5 cm** in diameter, filled with serous fluid.

• Pustule

  An elevated lesion of any size filled with purulent material (pus).

Secondary Skin Lesions

Secondary lesions are depressed and manifest below the plane of the skin, often resulting from changes to primary lesions.

Types of Secondary Lesions

1. Scale
2. Crust
3. Excoriation
4. Fissure
5. Erosion
6. Ulcer
7. Scar

Definitions of Secondary Lesions

• Scale

  A dry or greasy laminated mass of keratin; pathological exfoliation involving the epidermis (variable size and color).

• Crust (Scab)

  Dried blood, serum, or pus mixed with epithelial and bacterial debris.

• Excoriation

  A linear or punctate abrasion produced by mechanical trauma, often associated with pruritus (itching).

• Fissure

  A linear crack or cleft extending through the epidermis, often into the dermis. Varies in shape, size, and moisture content.
  • Often occurs in thickened and inelastic skin due to dryness and inflammation.

• Erosion

  Loss of portions or all of the epidermis only.
  • Heals without scar tissue. Areas of erosion are sometimes referred to as *denuded*.

Dermatological Skin Assessment Mnemonic (DERMATOLOGICAL)

• **D:** Describe Integrity
• **E:** Examine Skin Pigmentation
• **R:** Review Sensory & Soft Tissue Status
• **M:** Moisture
• **A:** Atrophic Changes
• **T:** Turgor and Texture
• **O:** Observe Hair and Nails
• **L:** Look & Feel Edema, Color, Temperature
• **O:** Observe Skin Folds (e.g., between toes)
• **G:** Gerontodermatological Changes (Age-related)
• **I:** Inquire about Allergies, Sensitivities, Co-morbidities
• **C:** Callus Present?
• **A:** Assess Vascular Status
• **L:** Lesions (Location, Presentation)

Eczema and Dermatitis

Environmental Causes

• **Irritants:** Soaps, detergents, fruit acids, etc.
• **Allergies:** Dust, pets, pollen.
• **Microbes:** *Staphylococcus*, viruses.
• **Extreme Temperatures:** Humidity.
• **Foods:** Dairy, eggs, nuts, seeds, wheat.
• Stress
• Hormones

Types of Eczema

Atopic Eczema/Dermatitis (Most Common Form)

A chronic, relapsing type characterized by itchy, inflamed skin.

• Xerosis (dryness).
• Itchy, flaky patches with or without scales.
• Excoriations due to constant scratching.
• Not contagious.

Common Areas of Atopic Eczema

• Inner elbows
• Behind the knees
• Can appear anywhere

Lichenification

Thickening of the epidermis with exaggeration of normal skin lines, usually due to chronic scratching.

Nummular/Discoid Eczema

Causes coin-shaped patches of irritated skin that may spread.

• Oozing, crusted, scaling, itchy.
• May occur after an injury to the skin.

Most Common Areas for Nummular/Discoid Eczema

• Arms
• Back
• Buttocks
• Lower legs

Contact Eczema Types

• **Allergic:** Red, itchy, weepy.
• **Irritant:** The most common type.

Seborrheic Eczema

Forms scaly, oily, yellow patches on the skin.

Common Locations

• Scalp
• Face
• Upper chest
• Back

Stasis Eczema

Skin irritation of the lower leg usually related to circulatory problems.

Xerotic Eczema (Winter Itch)

Irritated skin that occurs when the skin becomes abnormally itchy, dry, and cracked.

• Can appear with red bumps or scaly patches.

Treatment for Dermatitis/Eczema

There is no cure, but management focuses on:

• Identify causative factors.
• Steroid ointment (topical).
• Oral steroids for inflammation.
• Light therapy.
• Dressings.

Urticaria (Hives)

• Acute Urticaria

  Caused by foods, medications, exposure to allergens, or chemicals.

• Chronic Urticaria

  Allergic-like reactions occurring daily or almost daily for six or more weeks.

• Physical Urticaria

  Caused by physical stimuli such as cold, cholinergic factors, dermographism, pressure, or solar exposure.
  • May develop after exercise or other modalities.
  • Requires checking the skin for response to stimuli.

Treatment of Urticaria

• Antihistamines.
• Colloidal baths.
• If severe, epinephrine may be necessary.
• Usually resolves when the causative agent is removed.

Psoriasis

Psoriasis is a chronic, recurrent inflammatory autoimmune condition that causes a thick, patchy, red rash with silvery-white scales.

• Most common ages: 30–50 years.

Common Locations

• Scalp
• Nails
• Ears
• Extremity surfaces (extensors)
• Elbows
• Knees
• Umbilical region
• Sacral regions

Symptoms of Psoriasis

• Rashes or patches of red, inflamed skin with silver scales.
• Stinging or burning sensation.
• Nail discoloration, pitting, and fragility.

Common Triggers for Psoriasis

• Skin injury or infection.
• Emotional stress.
• Certain medications.
• Smoking and alcohol consumption.
• Cold or dry weather.

Types of Psoriasis

1. Plaque Psoriasis
2. Guttate Psoriasis
3. Inverse Psoriasis
4. Erythrodermic Psoriasis
5. Pustular Psoriasis

Plaque Psoriasis

Raised, inflamed, red lesions covered with silvery scales (e.g., elbows, knees, scalp, lower back).

Guttate Psoriasis

Small, red, individual spots on the skin (e.g., torso, arms, legs). Not typically very thick.

Inverse Psoriasis

Appears as bright red lesions that are smooth and shiny, typically found in skin folds.

Erythrodermic Psoriasis

An inflammatory form affecting most of the body surface.

• Widespread, periodic, fiery redness.
• Shedding of scales in sheets.

Pustular Psoriasis

White blisters of non-infectious pus surrounded by red skin, often covering most of the body.

Treatment for Psoriasis

There is no cure, but treatment aims to convert the disease from an active to a latent stage.

• Moisturize skin.
• Topical steroids and immunosuppressives.
• Laser therapy.
• UV therapy.
• Colloidal baths, coal tar preparations.

Approximately **10–30%** of people with psoriasis develop psoriatic arthritis.

Benign Skin Tumors and Vascular Lesions

Melanocytic Nevi (Mole)

A disorder of the melanocytes.

***Refer out if a mole develops rapidly, changes in size/color, weeps, bleeds, or becomes itchy.***

Congenital Melanocytosis (Mongolian Spot)

Congenital blue-gray or blue-black macular lesions.

• Appear at birth, typically on lumbosacral areas or buttocks.
• No treatment needed.
• Usually disappear in early childhood.

Capillary Hemangiomas (Strawberry Marks)

Benign, soft lesions usually occurring on the head or neck.

• Bright red or deep purple vascular nodules or plaques.
• Usually appear 1–4 weeks after birth.
• Usually disappear by age 5.
• Associated with low birth weight and 5x more likely in women.

Port-Wine Stains (Nevus Flammeus)

Irregularly shaped, red, macular, vascular birthmark due to absent or insufficient supply to nerve fibers.

Common Areas

• Neck, face, scalp, arms, legs.

Development Over Time

Often gets darker and may thicken, feeling like small pebbles under the skin in adulthood.

Treatment

Not necessary, but laser therapy, prednisone, or skin grafts can help make them less noticeable.

Cherry Angiomas

Asymptomatic, bright red, domed vascular lesions.

• Benign abnormal proliferation of blood vessels.
• Common in older individuals, typically on the trunk.
• Bleed significantly when injured.

Seborrheic Keratosis

The most common benign epithelial tumor.

• Initially flat, well-demarcated, small, brown pigmented areas.
• Over time, they become raised, darker, soft, and crumbly.
• Common in older people.

Acrochorda (Skin Tags)

Soft, round, skin-colored benign tumors ranging in size.

• Common in the elderly, obese individuals, and women.
• Common areas: Neck, armpits, groin.

Lipomas

Single or multiple fatty tumors; the most common benign form of soft tissue tumor.

• Develop slowly, easily moveable beneath the skin, and painless.

Skin Cancers and Malignancies

Basal Cell Carcinoma (BCC)

Arises from the basal layer. A persistent, non-healing sore is a common sign.

• Presents as small, pink-colored nodules that enlarge over time.
• **Most common form of skin cancer.**
• 80% of BCC lesions present on the head, neck, and face.

Treatment

Aggressive excision.

Squamous Cell Carcinoma (SCC)

Abnormal cells arise from squamous cells.

• Presents as persistent scaly red patches or elevated lesions with irregular borders.
• 40% will have recurrence.

Common Areas

Rim of the ear, lower lip, face, scalp, neck, hands, arms, legs, and all areas of the body, including mucous membranes and genitals.

Treatment

Surgical excision or cryotherapy.

Malignant Melanoma

A rapidly progressing, metastatic tumor of melanocytes.

Common Locations

• **Men (M):** Back, trunk, head, neck.
• **Women (W):** Lower leg and arms.

Characteristics

• Irregular borders, uneven surfaces, black/brown pigmentation.
• Red, inflamed, tender area.
• May bleed or ulcerate.
• May resemble or arise from moles.

Treatment

• Early recognition is key.
• Surgery, cryotherapy.
• Chemotherapy, radiation.
• Laser therapy.
• Immunotherapy.

Criteria for a Suspicious Lesion

A lesion should be considered suspicious if it exhibits:

• Rapid growth over weeks to months.
• Diameter **≥ 6 mm**.
• Changes in pigmentation.
• Inflamed margin.
• Irregular borders.
• Crust formation.
• Bleeding or itching.

ABCDE Criteria for Melanoma Detection

• **A:** Asymmetry
• **B:** Borders (Irregular)
• **C:** Color (Varied)
• **D:** Diameter (≥ 6 mm)
• **E:** Elevation/Evolving (Changing over time)

Kaposi’s Sarcoma (KS)

Malignancy of cells lining blood vessels caused by a viral infection.

• Linked with Human Herpesvirus 8 (HHV-8) and HIV.
• Begins as a painless ecchymosis macule and evolves into larger lesions.
• Non-contagious.

Treatment of Kaposi’s Sarcoma

• Cryotherapy.
• Alitretinoin gel.
• Radiotherapy.
• Topical immunotherapy.
• HAART (Highly Active Antiretroviral Therapy) for AIDS patients.

Systemic Autoimmune Disease

Scleroderma (Systemic Sclerosis)

A progressive, inflammatory, incurable systemic autoimmune disease.

• Skin becomes hard, smooth, hypopigmented, and stiff.
• More common in women (W > M).

CREST Syndrome (Scleroderma Symptom Features)

• **C:** Calcinosis (calcium deposits, often in fingers)
• **R:** Raynaud’s phenomenon
• **E:** Esophageal dysfunction
• **S:** Sclerodactyly (tightness and thickening of the fingers and toes)
• **T:** Telangiectasia (spider veins)

Skin Infections

Bacterial Infections (Impetigo and Ecthyma)

Caused by *Staphylococcus aureus* or *Streptococcus pyogenes*.

• **Impetigo:** Affects the epidermis (superficial).
• **Ecthyma:** Penetrates deeper into the dermis.

Contributing Factors

• High temperatures or humidity.
• Age (often children).
• Crowded living conditions.
• Poor hygiene.

Non-Bullous Impetigo

The most common form. Starts as red papules, rapidly evolving to small blisters, then pustules that scab over.

Bullous Impetigo

Large blisters on exposed parts of the body that rupture, leaving erosions that last days to weeks.

Most Common Areas for Impetigo

• Nose, mouth, hands, forearm.

Ecthyma

A more serious form of impetigo that penetrates deeper into the skin, causing pus-filled sores that turn into ulcers.

• Common in areas of previously sustained tissue injury, immunocompromised individuals, and the elderly.
• Lasts weeks to months and tends to scar.

Treatment

Antibiotics.

Deep Infections and Abscesses

• Abscess

  Begins as a tender red nodule that develops into a collection of purulent material with fluctuance.

• Furuncle (Boil)

  Firm, tender nodules, usually near hair follicles, 1–2 cm in diameter.

• Carbuncle

  A deep extension of two or more coalescing furuncles.

• Cellulitis

  Acute infection of the dermis and subcutaneous tissue. Symptoms include localized tenderness, malaise, fever, chills, and regional adenopathy.

Viral and Fungal Infections

Herpes Zoster (Shingles)

After infection with chickenpox, the virus lies dormant in the **dorsal root ganglia**.

Tinea Pedis (Athlete’s Foot)

A fungal infection. Spores can live up to one year in skin scales.

• Symptoms: Erythema, pruritus, scaling, maceration, bulla formation.

Candidiasis (Yeast Infection)

High-risk patients include those with diabetes, immunocompromised status, chronic steroid use, or long courses of antibiotics.