Integumentary System

Integumentary Anatomy

Review:

  • Collagen - the main structural protein found in skin and other connective tissues

  • Corium - the deep vascular inner layer of the skin; dermis

  • Cutane(o) - pertaining to the skin

  • Dermis - the deep vascular inner layer of the skin

  • Epithelium - the cells that make up the outer surface of the skin; it is also layers of cells that line hollow organs and glands

  • Kerat(o) - pertaining to horny tissue; hard; pertaining to the cornea

  • Seb(o) - pertaining to sebum (oil)

New:

The term onchy(o) means claw or nail. A dewclaw is a vestigial or rudimentary digit present in some dogs

Hidr(o) means sweat. Hidrosis is the production and excretion of sweat. 

Trich(o) means hair. 

In the last module, we learned about allergens and allergic responses. A histamine is a chemical released in response to an allergen that is produced by basophils.

Integumentary Pathology

Appearance:

Alopecia is hair loss resulting in bald spot or complete lack of hair. 

On naturally or pathologically alopecic areas, we can examine the skin for abnormal presentations such as:

Albinism- Genetic based lack of melanin production leading to a white appearance to the skin.

Erythema - skin redness. Recall red blood cells are called erythrocytes.

Cyanosis- abnormal blue coloration to the skin typically due to low oxygen content of the blood or poor perfusion.

Jaundice/Icterus- Yellow discoloration from hyperbilirubinemia.

Pallor refers to an unhealthy pale appearance.

Hyperpigmentation occurs secondary to some inflammatory conditions to the skin.

Bleeding disorders can cause blood to collect from minor bumps and bruises (the type we experience every day with no consequence).   If an animal has a bleeding disorder, you might see

Hematoma- Bleeding under the skin

Petechia  - A  small collection of blood in the skin (<0.5cm in diameter).

Ecchymosis - a large collection of blood in the skin l(>0.5cm in diameter).

Petechia (small) and Ecchymosis in a dog with thrombocytopenia from a tick-borne disease.

Itchy:

Pruritus is the term that describes severe itching of the skin.

Atopy is a hypersensitivity or allergic reaction to an allergen which is also called allergic dermatitis.

Atopy should not be confused with acute moist dermatitis which is a skin condition characterized by localized lesions also known as "hot spots".   Acute moist dermatitis is worsened through licking or scratching and is more common during summer months. 

 

Damage and Injuries:

An abrasion is an injury in which only the superficial layers of the skin are scraped.  A laceration is a cut or tear in the skin. 

A crust is a scab made up of tissue fluid or blood leaking through a wound.

A fissure of the skin is a crack-like sore and an ulcer is the erosion of skin or mucous membrane. 

A lesion is an abnormal change in tissue caused by damage through injury or disease. 

Gangrene is tissue necrosis associated with a loss of circulation. The extremities are often affected first, but gangrene can also occur internally. 

A contusion is an injury that does not break the skin, but causes pain, swelling, and discoloration. Contusions are also called bruises or hematomas.   You can have contusions in the parenchyma of other organs; for example, it is common to see pulmonary contusions in animals with thoracic trauma.

 

Lumps and bumps:

Pyodermas, a group of skin diseases involving the formation of pus (pyo-), can take many forms as you can see in the graph below. 

An abscess is closed pocket containing pus.   While they can occur anywhere, the skin is a common location.

A comedo is the buildup of sebum and keratin in pores. Comedones are also called blackheads.

A pustule is a small pus-filled skin elevation such as a pimple or blister.

A boil or furuncle is also a localized skin infection, typically slightly larger than a pustule.

Urticaria are localized areas of swelling that itch, also known as hives. 

A verruca is a wart. Verrucae are small growths of rough texture that are usually caused by viruses. 

Integumentary Procedures

Cauterization and cryosurgery are both procedures that destroy diseased tissue. Cauterization destroys tissue with heat, chemicals, or electric current while cryosurgery destroys tissue with extreme cold. 

Debridement is the removal of damaged tissue and foreign material from a wound to aid in healing.

To lance means open or puncture with a lancet (scalpel blade) to allow drainage. 

Exfoliative cytology is the scraping of skin cells for microscopic examination. 

Integumentary Video- Skin Diseases

The Skin

  • A good indicator of internal disease

  • Any condition that disrupts this barrier can cause disease (pathogens can now pass through!)

  • Skin issues are the most common complaint in small animal med.

Ectoparasites

Otodectes Cynotis

  • Ear mites

  • Live in the external ear canal

  • Clinical signs:

    • “Coffee ground” substance in ear

    • Severe itching causing wounds around ears from scratching with nails.

  • Diagnosis

    • Ear swab and microscopic exam

  • Treatment

    • Clean ears and apply a flea/worm control product that covers ear mites

    • There is also a treatment that is put directly into the ear canal called MilbeMite

    • May need to treat 2-3 times to be successful

    • Not zoonotic

Ctenocephalides Felis

  • Fleas

  • Can cause an allergic dermatitis (FAD)

  • Can be an intermediate host (often tapeworm)

  • Clinical signs

    • Scratching/biting skin- commonly around the tail base and inner thighs

    • Small scabs on the skin

    • Pepper-like granules can be seen on skin

      • Flea dirt. Looks red on a wet paper towel

  • Diagnosis

    • Physical exam- seeing a flea or flea dirt

  • Treatment

    • Sprays, powders, shampoos, dip and systemic antiparasitics

    • Vet systemic antiparasitics are the easiest, safest, and most efficient option.

    • Given topically or PO

    • Should be repeated monthly for at least 3 months

Mange Mites

  • a skin disease of mammals caused by parasitic mites. It typically causes severe itching, hair loss, and the formation of scabs and lesions.

Demodectic Mange

  • Demodex canis

  • Cigar-shapes mite

  • Normally lives in hair follicles

    • Very common in dogs, but patients with good immune systems do not show signs

    • If immunocompromised or stressed (poor nutrition, other parasites or infections, puppies), they will cause clniical signs, multiply and become a problem

  • Clinical Signs:

    • Alopecia around the eyes, mouth, and ears

    • Red, irritated skin

    • Not itchy, but can have skin infections, greasy coat and they will smell bad.

  • Diagnosis:

    • Skin scrapping- make sure to scrape deeply enough that there is slight bleeding

  • Treatment

    • Ivermectin in mature dogs with generalized demodectic mange; usually “benign neglect” for puppies with milder cases (localized)

    • Not zoonotic; not contagious to other dogs

    • Treatment can be long-term and will not eliminate all mites

Sarcoptic Mange

  • Sarcoptes Scabei

  • Scabies

  • Very itchy and contagious

  • Females burrow into the epidermis and lay eggs

  • Humans may develop lesions after exposure to an infected animal, but the mites cannot survive off the animal host and will die quickly.

  • Clinical Signs

    • Red/crusty lesions on ears, elbows, and trunk

    • Intense pruritus

    • Secondary skin infections due to scratching

    • Progressively gets worse

  • Diagnosis

    • DEEP skin scraping and microscopic exam

  • Treatment

    • Dips to remove mites (lime sulfur)

    • Ivermectin PO or SQ q14d

    • Revolution (applied q2-3 wks)

Fungal Infections

Microsporum Canis

  • Most common cause of “ringworm”

  • Large, rapidly growing circular pathces of alopecia

    • Some areas will be raised, red, and crusty

  • Often on the face and head

  • Diagnosis

    • Use a black light and the infected hair may fluoresce

    • Skin scraping/trichogram (hair pluck)- view microscopically

    • Fungal culture (slow but definitive)

      • Send to external lab

      • “Fungassay” in-clinic

  • Treatment

    • Clip hair (clean clippers well because they are now contaminated)

    • Treat affected area(s) with a topical antifungal q12h until 2 weeks after resolution of signs

    • For generalized dermatophytosis, antifungal shampoos (and expensive oral meds) are available.

  • Client Info

    • Contagious and zoonotic

    • Clean enviro thoroughly and repeatedly because hair that was shed is infective for 18 months.

    • Handle infected animal as little as possible

    • Treatment can take long time

Pyodermas

Acute Moist Dermatitis

  • “Hot Spots”

  • Rapidly appearing lesions, red/moist/hot and painful

  • Common in heavy-coated water dogs

  • Common in summer months

  • Clinical Signs

    • Rapidly appearing lesion

    • Localized alopecia

    • Pruritus

  • Diagnosis

    • Physical exam

  • Treatment

    • Clip area (be gentle because its painful)

    • Clean area with antibacterial soap (rinse well, don’t leave soap on- will cause irritation)

    • Dry well, then use topical meds 2-3x daily until healed

    • Place e-collar so dog doesn’t chew at themself.

Acne

  • Common in young, short-haired dog breeds, but usually resolves on its own

  • Tends to be a chronic issue in cats

  • Clinical Signs

    • Swollen chin +/- dark sports

    • Pimples on skin

  • Diagnosis

    • Physical exam

  • Treatment

    • Clip hair

    • clean with soap daily

    • Antibiotics if necessary

    • Use stainless steel or ceramic food/water dishes

Skinfold Pyoderma

  • Affects animals with a lot of oflds in face/vulva/tail

  • Folds trap moisture and heat; rubbing causes trauma and secondary infections

  • Chronic, long-term treatment

  • Diagnosis

    • Foul odor/discharge from affected area

  • Treatment

    • Clip/clean area and dry it well

    • Use topical ointment

    • Surgical removal of excess skin is the only real cure

    • Keep skinfolds dry at all times.

Deep Pyodermas

  • Tend to become chronic infections

    • Often resistant to treatment

  • May occur in animals with immuno-supression or allergy

  • Staphylococcus intermedius involved

    • Produces toxins and enzymes that cause severe tissue damage.

  • Conditions include juvenile pyoderma (puppy strangles), interdigital pyoderma (interdigital cysts), and generalized pyoderma

  • Clinical signs and treatments of all deep pyodermas are similar

  • Clinical Signs

    • Papules and pustules with crusting in characteristic locations

    • Fever

    • Draining tracts with severe infection

  • Diagnosis

    • Often based on clinical signs

    • Culture and sensitivity

    • Biopsy

  • Treatment

    • Daily cleaning

    • Antibiotic creams, sprays, or solutions 2-4x daily

    • Systemic antibiotics chosen from the C&S results

      • A good gram-pos spectrum drug

      • May need to treat for 3 months.

  • Info for Clients

    • The organism that is responsible for deep pyodermas is often drug resistant

    • Treatment may be prolonged and expensive in large-breed dogs

    • Should look into possible predisposing conditions

      • Ex. diabetes mellitus & Cushings disease

    • Some animals will never recover.

Anal Gland Issues

Anal Gland Conditions

  • The anal sacs create a special set of problems in companion animals

    • Most common: impaction, chronic infection, and rupture or abscessation.

  • Normally, when feces pass over the sacs, the sacs are compressed expelling some of the fluid onto the surface of the fecal material

    • If that fluid becomes too thick or the duct is blocked, the sacs will overfill

    • As water is reabsorbed from the fluid, the material dries out and causes impaction of the sac

      • Infection and impactions may result in anal sac rupture or abscessation

      • More common in small-breed dogs

  • Clinical Signs

    • History of “scooting” or licking excessively at the perianal area

    • Foul odor

  • Diagnosis

    • Digital palpation of distended anal sacs (rectally or externally)

  • Treatment

    • Express contents of the distended sac

    • Lavage the infected sac with LRS or saline

    • Instill antibiotic ointment into the sac

    • Oral antibiotics may speed healing time

    • Chronically infected sacs should be surgically removed

    • Remember to empty the opposite sac when treating a unilateral infection.

  • Info for Clients

    • Owners should be shown how to check +/- empty their pets anal glands

    • Scooting on the floor does not usually mean that the pet has worms (but it can…)

    • Blood under the tail may indicate a ruptured AG

    • Impactions and infections tend to recur

Tumors of the Skin

Skin Tumors

  • Tumor: new growth of tissue characterized by progressive, uncontrolled proliferation of cells

  • Can be benign (do no harm) or malignant (may result in death)

    • localized or invasive

  • Malignant tumors usually consist of poorly differentiated cells that metastasize to other parts of the body

    • Also invasive to surrounding tissues

    • Usually carcinomas (epithelial origin) or sarcomas (connective tissue origin)

  • 37% of canine and 24% of feline tumors involve the skin

  • Most skin tumors occur in older dogs (>6 yrs) and cats (>4 yrs)

    • Younger dogs are more likely to acquire viral-induced tumors

  • Breeds such as Boxers and Cocker Spaniels appear to be more susceptible to skin tumors

Benign Skin Tumors:

Histiocytomas

  • Clinical Signs:

    • Found almost exclusively in young dogs

    • Small, buttonlike nodules, usually pink

    • Usually hairless and may be ulcerated

    • Found on the face, legs, lips, and abdomen

    • Rapidly growing lesion

  • Diagnosis

    • General appearance

    • Biopsy

  • Treatment

    • Local surgical excision

    • Many tumors regress spontaneously

  • Info for Clients

    • Not malignant and do not metastasize

    • Note seen in cats

    • Lesions may regress spontaneously

      • Surgical excision still the treatment of choice

Lipomas

  • Clinical Signs

    • Obese, older dogs commonly affected

    • Affects females more than males

    • Round/oval subcuticular masses

    • Encapsulated, slow-growing masses

    • Soft, freely movable

  • Diagnosis

    • Biopsy

    • FNA will provide a presumptive diagnosis

      • Grey, greasy, mucoid substance- removed from the slide by the fixative solution while staining

  • Treatment

    • Surgical excision is the treatment of choice

    • Care should be taken to close the tissue space that results from removal of the mass

      • Otherwise seromas can develop

  • Info for Clients

    • Rarely become malignant

    • May recur after removal

    • Diet change will probably not affect existing lipomas

    • Benign tumors, but may grow very large.

Papillomas

  • Clinical Signs

    • Young dogs commonly affected

    • Begins as a smooth white elevated lesion in the oral mucosa

      • Develops into cauliflower-like growths

    • May regress spontaneously

    • Caused by virus

  • Diagnosis

    • General appearance

    • Biopsy

  • Treatment

    • Surgical excision of large masses may stimulate regression of others

    • Autogenous vaccines can be made from the dogs own tumor (rare)

    • Lesions usually regress without treatment

  • Info for Clients

    • Caused by a DNA virus

    • Disease may last as long as 21 wks

    • Older dogs are resistant

      • Cats unaffected

    • Usually regresses spontaneously and adult animals are immune for life.

Sebaceous Cysts

  • Clinical Signs

    • May occur in dogs of any age or sex; more common in Cocker spaniels

    • Cysts are encapsulated, round, and fluctuate on palpation.

      • When compressed, they may exude a gray cheese-like material

    • Enlarge slowly; may spontaneously rupture

    • May be found on the back, legs, chest, and neck

  • Diagnosis

    • Characteristic contents of the cyst

    • Histology

    • of cyst wall

  • Treatment

    • Surgical removal of entire cyst

  • These growths are formed by degenerative changes in the glandular area surrounding the hair follicle

  • Sebaceous cysts are benign growths

  • Surgical removal will cure the problem

  • These lesions are usually slow-growing

  • Dogs may have multiple lesions at varying times, especially in predisposed breeds.

Malignant Skin Tumors

Basal Cell Carcinoma

  • Basal cell carcinoma is a common tumor of adult animals (cats>dogs)

  • Clinical Signs

    • A single, discrete lesion: round, firm, often ulcerated

    • Most commonly found on the head (around the eyes), ears, lips, neck, and legs

    • Slow-growing

  • Diagnosis

    • Biopsy

  • Treatment

    • Wide surgical exceision

  • Info for Clients

    • These tumors rarely metastasize

    • Local recurrence after surgery is possible

    • Prognosis is not as good for animals with multiple lesions

Mast Cell Tumors

  • Clinical Signs

    • Isolated , firm nodules in the skin

      • 50% found on rear legs, perineum, or external genitalia

      • May be ulcerated and edematous

    • Usually seen in dogs >6yrs and cats >10 yrs

    • Siamese and male cats are predisposed

    • Lesions may appear crusty in cats

      • When crusts are removed, ulcerated surfaces are exposed

  • Diagnosis

    • Biopsy

    • Impression smears may show mast cell granules

    • FNA

  • Treatment

    • Surgical recision w/lymph node exam to rule out metastasis

    • Chemotherapy

  • Info for Clients

    • Do not usually metastasize, but up to 30% may do so

    • Prognosis depends on amount of cell differentiation within the tumor

      • Dogs: survival times range from 18-51 wks

      • Cats: lesions are usually benign

    • Recurrence at the surgical site is possible

    • A virus may cause these tumors

Melanomas

  • Clinical Signs

    • Benign lesions are usually small, slow-growing, hairless growths with dark pigmentation

    • Malignant growths are usually large, dome-shaped, non-movable growths of varying pigmentation.

    • Most commonly occur in the highly pigmented tissues of the dog (oral, skin, digits)

  • Diagnosis

    • Biopsy

  • Treatment

    • Surgical resection

  • Info for Clients

    • Tumors of the oral cavity and digits usually malignant

      • Metastasize readily

    • Because of early metastasis, the prognosis is often poor

    • Recurrence after surgery is common

    • Dogs w/small lesions have a median survival time of 12 months (54% are dead within 2yrs)

      • Large lesions: survival time is 4 months (100% dead w/in 2 yrs.)

Other Malignant Tumors

  • There are other common skin tumors

    • Perianal adenomas/adenocarcinomas

    • Squamous cell carcinomas

  • Diagnosis and treatment are similar