Dip M1: Diseases of skin and subcutaneous tissue

What is an abscess?

Large pus-filled cavity, surrounded by inflammation.

What is a cyst?

Closed sac under the skin, filled with fluid or semisolid material. (e.g., sebum).

What is an ulcer?

Open sore with tissue breakdown or erosion.

What is a lesion?

Any damaged tissue (injury or disease)

or
A lesion is any abnormal change in the skin or body tissue.

It could be a spot, lump, sore, or area of damage.

What is a vesicle vs. a bulla?

• Vesicle = Small blister (<0.5 cm), fluid-filled.

• Bulla = Large blister (>0.5 cm), fluid-filled.

What is a pustule?

Small pus-filled bump.

What is erythema?

Redness of the skin due to increased blood flow.

What is ecchymosis?

• Purple/black skin discolouration caused by bleeding under the skin.

• If caused by trauma, it’s called a bruise.

What are café-au-lait spots?

Flat, light brown skin patches, similar to the colour of milky coffee.

What is urticaria?

• Raised, itchy skin patches from an allergic reaction.

• Also called wheals, hives or welts.

What is desquamation?

Peeling of the skin.

What is excoriation?

Shallow ulcers caused by scratching.

What is a fissure?

Deep skin crack or slit.

What is cicatrix?

Scar left after healing.

What is exudate?

• Fluid that seeps (flow or leak) from tissues.

• Can be purulent (pus), sanguinous (bloody), or serous (watery).

What is seborrhoea?

Excess oil production from sebaceous glands.

What is alopecia?

Hair loss from areas where it normally grows.

What is pruritus?

Itching

What is macule?

Flat discolored spot (<1 cm).

What is milia?

Tiny white bumps under the skin.

What is a nodule?

Solid lump (>1 cm).

What is a papule?

• Small, solid, raised bump (<0.5 cm).

• Also called a pimple.

What is a plaque?

Large, raised, scaly lesion (>1 cm).

What is an ulcer?

An ulcer is an open sore or crater in the skin caused by tissue breakdown.

What is chloasma?

Brown/yellow skin patches.

What is lividity?

Bluish skin due to blood pooling (accumulation of blood).

What is petechiae?

Tiny pinpoint red spots.

What is purpura?

Reddish-purple spots (3–10 mm).

What is dysplasia?

Abnormal tissue growth.

What is granulation?

Healing tissue formation.

What is purulent exudate?

Pus

What is sanguinous exudate?

Bloody fluid

What is serous exudate?

Watery fluid

What is dermatitis?

Inflammation of the skin.

What is an eruption?

Rash or outbreak.

What is psoriaform?

Resembling psoriasis (scaly skin)

What is pyoderma?

Purulent (pus-filled) skin disease.

Acne Vulgaris

Acne vulgaris (commonly known as acne) is a chronic skin condition caused by clogged sebaceous glands and trapped keratin. This leads to inflammation, forming open or closed comedones like blackheads and white heads.

It is hormone-driven and commonly occurs during puberty.

Seborrhoeic Dermatitis

Chronic skin condition that causes oily, itchy, and scaly.

Commonly affects scalp, face, & chest → Areas rich in sebaceous (oil) glands.

Acne Rosacea

Chronic facial redness, NO comedones, but can have papules & pustules.

More common in fair-skinned individuals

Acne Neonatorum

Acne Neonatorum is a newborn baby acne caused by maternal hormones stimulating baby's sebaceous glands.

Contact Dermatitis

Inflammatory skin reaction caused by something that touches the skin.

What sets it apart from urticaria:

• lesions remain longer

• may require topical treatment

• not an allergic reaction

Psoriasis

a chronic autoimmune skin condition that causes patchy areas of erythema (redness of the skin) + white scales due to rapid skin cell turnover.

Cellulitis

A bacterial infection of the dermis and subcutaneous fat (deeper layers of the skin).

Appears as a red, swollen area with ill-defined borders (not clearly outlined).

Often hot to the touch, especially near the infected site.

Usually caused by bacteria entering through broken skin (like cuts, scrapes, or insect bites).

Impetigo

Impetigo is a bacterial infection of superficial skin characterised by yellowish crusts on the skin.

It is highly contagious and spreads by contact.

Warts or verrucas

Warts are skin growths caused by the human papillomavirus (HPV).

The virus causes the skin to thicken in the epidermal layers (corneum, spinosum, and granulosum), leading to a protruding lesion (wart).

It gains access through damaged skin.

Herpes Simplex Virus (HSV)

Contagious

• HSV-1: Causes oral herpes (cold sores), usually in childhood.

• HSV-2: Causes genital herpes (blisters or ulcers).

VZV (Varicella Zoster Virus)

Contagious

Causes chickenpox (initial infection) and shingles (reactivation).

• Chickenpox: Spread through airborne droplets (coughing, sneezing) or contact with blisters.

• After chickenpox, virus stays dormant in the body and may later reactivate as shingles

Dormant just means the virus is sleeping in the body, but it can wake up later

Furuncle

A furuncle is a boil, which is a painful and swollen bump, often filled with pus.

It usually occurs when a hair follicle becomes infected with bacteria.

Treatment typically involves incision and drainage.

Diabetic patients are at higher risk (immune system is weaker)

Carbuncle

A carbuncle is a larger and more severe version of a furuncle, often appearing on the back of the neck.

It consists of multiple boils that are joined together, with several openings where pus drains out.

Treatment typically involves incision and drainage.

Diabetic patients are at higher risk (immune system is weaker)

Paronychia

Paronchyia is a form of cellulitis that affects skin around the nails.

It is an infection around the nails, caused by bacteria (Staphylococcus aureus) or fungi (Candida albicans).

Commonly affected fingers: Index and middle fingers are the most commonly affected.

Frequent hand washing and injuries to the cuticle increase the risk.

If topical treatments don't work:

• Surgical debridement (removing infected tissue).

• Partial excision of the nail may be required in severe cases.

Calluses

Calluses are thickened patches of dead skin that form due to friction or pressure.

Mainly caused by friction (rubbing) or grinding pressure. On the feet, it’s often due to poorly fitting shoes, while on the hands, it’s caused by activities like construction work, handicrafts, or sports.

Some calluses resolve on their own once the friction or pressure is removed.

Corns

Corns are cone-shaped calluses that are directed inward, causing pain as they press on underlying tissues.

Lupus Erythematosus

An autoimmune condition causing erythematous macular lesions (red spots), often in a butterfly pattern across the face, photosensitive rash, and may affect joints, kidneys, lungs, and heart.

• Systemic Lupus Erythematosus (SLE): When lupus affects internal organs, diagnosed as SLE, the most severe form.

• No cure, but management is aimed at reducing symptoms and preventing damage to organs.

Scleroderma

Scleroderma is a systemic autoimmune disease causing overgrowth of connective tissue.

The skin becomes smooth, hard, and tight, which can affect movement and breathing.

Localized scleroderma: Affects mainly the skin, and patients can live a normal lifespan.

Widespread scleroderma: Involves multiple organs and can be fatal.

Treatment is symptomatic (managing or relieving the symptoms).

Basal Cell Carcinoma (BCC)

• Malignant tumour in the stratum basale (bottom layer of the epidermis)

• Most common skin cancer

• Grows slowly and rarely spreads to other parts of the body

• Caused mainly by UV exposure, especially in children and fair-skinned people

• Treated by surgical excision (removal)

Squamous Cell Carcinoma (SqCC)

• Malignant tumour of squamous epithelial cells (found in skin and other organs)

• Can appear in the skin, mouth, oesophagus, bladder, vagina, etc.

• Linked to HPV infection and possibly diet

Melanoma

• Cancer that starts in melanocytes (cells that give skin its pigment)

• can occur in pre-existing mole

• Most dangerous type of skin cancer because it spreads easily to lungs, liver, brain

• Caused mainly by UV light exposure in fair-skinned people

• Treated by surgery, sometimes chemotherapy

• Prevention: sun protection

Kaposi's sarcoma (KS)

• Malignant tumour of small blood vessels under the skin

• Appears as painless, purple patches or lumps

• Caused by HHV-8 virus + immunosuppression (especially HIV)

• No cure, and it spreads (metastasises)

• Common in people with HIV → it’s an AIDS-defining illness

• Prevented by preventing HIV transmission

Benign

Non cancerous / harmless

Malignant tumour

A cancerous growth.

It grows fast, can invade nearby tissues, and spread to other parts of the body.

Burn

A burn is skin damage caused by excessive heat, radiation, chemicals, electricity, friction, or sunlight.

It leads to:

• Death of skin cells

• Fluid loss, which can cause dehydration, kidney, and heart failure

• Increased risk of infection, since the skin barrier is damaged

Decubitus Ulcer

Also called bedsore or pressure ulcer

It's a wound that forms when someone stays in one position for too long without moving—especially over bony areas like: heels, hips, coccyx (tailbone) and elbows.

The constant pressure cuts off blood flow to the skin.

Without blood, the skin and tissue start to die (this is called necrosis).

Embolic Gangrene

Embolic gangrene is a specific type of gas gangrene caused by a blockage in blood flow from an embolus (a clot or object traveling in the bloodstream)

Gangrene

Gangrene is the death of body tissue because of a loss of blood supply.

• Oxygen and nutrients are cut off

• The tissue becomes ischaemic (low oxygen)

• Then the tissue dies — this is called necrosis

Dry Gangrene

Slow and gradual blood flow loss

Often caused by arteriosclerosis (hardening of the arteries)

The skin becomes:

• Dry

• Shrunken

• Clearly outlined from healthy skin

• Common in people with diabetes → called diabetic gangrene

It spreads slowly and doesn't get infected right away.

Wet Gangrene

• Happens quickly when the blood supply is suddenly cut off

• Tissues become swollen, wet, and infected

  More dangerous because it can spread fast and lead to sepsis

Gas Gangrene

A type of wet gangrene that can occur after trauma such as a crushing injury, frostbite, tight bandages or a tourniquet, in which blood supply is cut off to the tissue.

• Bacteria grow in low-oxygen, damaged tissue

• Releases toxins and gas bubbles → swelling, rotting (putrefaction)

• Very dangerous — spreads quickly

• Treated by surgical removal of dead tissue (may need amputation)

Anaerobic

Anaerobic meaning they thrive in places with little or no oxygen

Necrosis

Death of a tissue.

Note:

Gangrene = necrosis + infection or severe blood supply loss

Embolic gangrene

Embolic gangrene is caused by a blockage in blood flow from an embolus (a clot or object traveling in the bloodstream).

Think of embolic gangrene as the trigger (sudden blockage) → and gas gangrene as what can happen after, if certain bacteria take advantage of the dead tissue.

Pilonidal cyst

A pilonidal cyst is a small sac under the skin in the natal cleft (the groove between your buttocks).

It usually contains hair and dead skin cells.

"Pilonidal" literally means "nest of hair."

If bacteria get into the cyst, it can become an abscess (a painful, swollen lump filled with pus). This is called a pilonidal abscess.

Sometimes, a sinus tract forms – a tunnel between the skin surface and the infected area deep inside. This is a pilonidal sinus. Not the nose!

In rare cases, the tunnel can even go the other direction and connect to the rectum.

Cryosurgery

Freezes and destroys abnormal tissue or lesions using freezing temperatures (liquid nitrogen or carbon dioxide).

Curettage of skin

Scraping off superficial skin lesions with a curette.

Superficial skin lensions = located on the outer layers of the skin (epidermis and sometimes the upper dermis)

A curette is a medical instrument used to scrape or scoop tissue

Dermabrasion

Surgical removal of the epidermal layer (top skin) in order to remove naevi (moles), tattoos or scars by using abrasives.

Electrodessication

Uses electric spark inside the skin to burn/destroy tissue

The electrode inserted into the skin.

Used to treat telangiectasias and spider naevi.

Excisional debridement

Surgically cutting away dead or infected tissue (done with scalpel/scissors)

Fulguration of skin

Like electrodessication but electrode is held above the skin, so damage is more superficial.

Used for treating superficial epidermal lesions.

Argon laser

Penetrates (1–2 mm deep); used for port wine stains, haemangiomas.

Carbon dioxide (CO₂) laser

Penetrates (0.1–0.2 mm deep); for tumours, debridement of ulcers and burns.

Debridement is the removal of dead (necrotic) or infected skin tissue to help a wound heal.

Erbium YAG and CO₂ combined laser

Used for laser resurfacing with less risk of deep burns.

It removes superficial wrinkles and other effects of aging/weathering on skin, without causing deeper burn injuries, which are experienced with CO₂ laser resurfacing.

Mohs’ surgery

(microscopically controlled surgery)—thin layers of a malignant skin cancer are removed and each layer is examined under a microscope. This continues until a totally cancer-free layer is removed. This is sometimes done over more than one session.

Skin grafting

A surgical procedure where skin is taken from a healthy area (donor site) and placed over a wound or area that has lost its skin (denuded area).

To cover wounds where there is insufficient skin for closure.

The wound to be grafted must be clean and free from bleeding.

By Source:

• Autograft – From same person (most common; inner thigh donor site).

• Isograft – From identical twin.

• Allograft – From same species (donor/cadaver).

• Xenograft – From different species (e.g., pig skin).

Types of Skin Grafts:

Free grafts (completely detached):

STSG (Split thickness) – Epidermis + part of dermis. Heals naturally.

FTSG (Full thickness) – All dermis. Donor site needs to be closed.

Meshed – Graft is cut into mesh so it stretches over bigger wounds.

Composite – Includes skin + other tissue (fat, cartilage, etc.).

CEA (cultured) – Skin cells grown in lab from a biopsy, then sprayed on wound (e.g., Fiona Wood’s spray-on skin).

Pedicle/Flap grafts – Part of the tissue remains attached to blood supply during transfer.

• Used for reconstructing complex wounds, e.g., over joints or bones.

Flaps

Flap is a block of tissue transferred from donor to recipient area along with its vascularity (blood supply).

Types of Flaps:

1. Local Flap: The tissue comes from a site next to the area that needs it. It's nearby, so the blood supply is easy to keep intact.

   • Example: A flap taken from the skin of your forehead to repair a wound on your forehead.

2. Distant Flap: The tissue comes from a farther area (not next to the wound). The blood vessels that keep the tissue alive may need to be moved along with it.

   • Example: A flap from your leg being moved to a wound on your face.

Methods of Moving Flaps:

This describes how the flap is moved to the wound area:

1. Direct Method: The flap is moved directly from the donor area (where the skin is taken) to the wound site. It doesn't pass through anything else.

   • Example: A flap taken from your arm and placed directly on your hand.

2. Indirect Method: The flap is moved through an intermediate site before reaching the wound. It's like taking a detour before getting to the destination.

   • Example: Moving a flap from your leg to your face, but first passing through the side of your chest.

Flap Types (Different Procedures or Styles of Moving Flaps):

1. Z-plasty: This is used to change the shape of a scar. It involves making a Z-shaped incision, which helps rotate or stretch the skin to fix the scar.

   • Purpose: Elongates scars or reduces tension.

2. V-Y Plasty: Involves cutting the skin in a "V" shape, stretching it apart, and then stitching it together to form a "Y." This technique helps to lengthen tissues.

   • Purpose: Lengthening tissue in one direction.

3. Cross-leg Flap: A flap is transferred from one leg to another, or even from one arm to another.

   • Purpose: When the area needing tissue can't be reached easily, so the flap is moved from another body part.

4. Rotation Flap: The flap is rotated from its donor site to cover the wound. It's a simple rotation of tissue from nearby to the wound.

   • Purpose: For covering a wound that's hard to reach with a straight cut.

5. Tubed Pedicle Flap: This is when a long flap of tissue is folded into a tube shape and moved to the recipient site while still attached to its blood supply at both ends.

   • Purpose: To cover a wound with tissue that needs to be stretched or folded.

6. Fasciocutaneous Flaps: These flaps are made from the skin and the underlying layer of tissue called fascia, which helps supply blood to the skin.

   • Purpose: Used when more blood supply is needed for the skin graft.

7. Muscle or Musculocutaneous Flaps: These flaps include both skin and muscle, which provides extra strength and blood flow.

   • Purpose: Used in cases where muscle tissue is needed for better healing and strength.

8. Free Flaps: This is when the tissue is completely detached from its original blood supply and reattached to the wound using special surgery (called microsurgery).

   • Purpose: Typically used for complex reconstructions, such as in the face or for covering tendons in the hand.

Bacterial Analyses

To detect the presence of microorganisms (bacteria) on the skin.

A sample is taken from the skin and cultured to identify the type of bacteria.

Fungal test

To identify fungal infections like ringworm, athlete's foot, or fungal nail infections.

Skin scrapings, hair specimens, or nail clippings are collected and examined under a microscope or cultured in a lab.

Intradermal test or skin test

• Identifies allergens by injecting small amounts of allergens under the skin.

• Results seen in 15-30 minutes.

• Positive if a raised bump (wheal) and redness (erythema) appear.

• No reaction at the control site.
  

Patch test

• Identifies allergens, especially for contact dermatitis.

• An adhesive patch with the allergen is applied to the skin.

• A control patch is placed next to it.

• After 24-48 hours, patches are removed.

• Positive result: Redness or swelling at the allergen site.

Scratch test

• Several scratches are made on the skin.

• A small amount of test material is inserted into the scratches.

• Used to test for allergens.

Mantoux test for tuberculosis (TB)

• A tiny amount of tuberculin is injected into the skin.

• 72 hours later, the injection site is checked for a raised, hardened area (induration).

• Positive result: Indicates TB exposure.

Skin Biopsy

• Skin Biopsy: A diagnostic procedure where tissue is removed from the skin to examine it under a microscope. This helps in detecting conditions such as skin cancer, infections, or inflammatory skin diseases.

• Punch Biopsy: A technique where a circular instrument is used to remove a small core (plug) of skin. It’s often used to obtain deeper layers of skin, especially for diagnosing skin conditions like rashes or skin cancers.

• Shave Biopsy: In this procedure, a small portion of skin is shaved off from the surface using a scalpel. It's typically used for superficial skin growths, such as moles or lesions. It doesn’t remove deep layers of skin like the punch biopsy.