Lecture 72: Endocrine & Nutritional Disease / Alopecia & Hair Cycle Disorders

What are the similarities and difference between alopecia and hypotrichosis?

alopecia is the complete absence of hair and hypotrichosis is partial absence of hair, but both arise from loss of hair shafts or failure to produce hair due to inflammation, trauma, ischemia, endocrinopathy, or genetic factors

What is traumatic alopecia?

alopecia from self-trauma (scratching, biting), excessive grooming, or friction → frictional alopecia occurs on areas subjected to chronic rubbing

What is inflammatory alopecia?

alopecia due to folliculitis (infectious or autoimmune), leading to follicle destruction and hair release

What is endocrine alopecia?

hormonal imbalances impair follicle cycling → follicles arrest in telogen or kenogen phases → results in follicular atrophy and non-inflammatory, systemic hair loss

What is ischemic (nutritional/traumatic) alopecia?

alopecia seen in cats post-trauma (ex. pelvic fracture alopecia) due to localized ischemia and atrophic skin

What is follicular dysplasia?

abnormal development of hair follicles causing patchy alopecia, abnormal or absent hair shafts, often symmetrical

What are examples of follicular dysplasia and genetic alopecias?

• congenital alopecia/hypotrichosis: complete or partial absence of follicles

• color dilution alopecia: linked to coat color genes

• hairless breeds

What is prolonged postclipping alopecia?

delayed regrowth in plush-coated breeds (e.g., Chow Chow) due to hair cycle arrest or clipping during telogen phase

What is traction alopecia?

chronic ischemia from tight bands or barrettes in longhaired dogs → localized, permanent hair loss

What is recurrent flank alopecia?

cyclic, well-demarcated bilateral flank hair loss, often in Boxers and Bulldogs; photoperiod and genetics implicated

How does hyperadrenocorticism (cushings) cause skin lesions?

glucocorticoids suppress hair growth (anagen inhibition) and cause catagen induction → bilateral symmetric alopecia sparing head/limbs, thin fragile skin, comedones, calcinosis cutis, poor wound healing, and seonceary infections

What are the firm ulcerated dermal plaques formed in dogs with Cushing’s?

calcinosis cutis from dystrophic calcification

How does feline hyperadrenocorticism affect the skin?

extreme skin fragility due to atrophic dermal collagen and decreased anagen follicles

What skin lesions are seen in adrenal-associated endocrinopathy in ferrets?

elevated sex steroids, rather than cortisol, causes symmetric alopecia possibly with pruritus

What skin lesions does hypersomatotropism (acromegaly) cause?

thick, folded skin (glycosaminoglycan accumlation), long dense hair coat, and hard claws due to excessive growth hormone due to progesterone-induced mammary GH secretion

How does hyposomatotropism (GH deficiency) cause skin lesions?

congenital pituitary underdevelopment in puppies → retention of puppy coat, stunted growth, and endocrine alopecia

How does hyperestrogenism cause skin lesions?

ovarian cysts/neoplasms in females or sertoli cell tumors or estrogen administration in males → symmetric alopecia (starting perineally), hyperpigmentation, gynecomastia, vulvar enlargement, or prostatic squamous metaplasia

What are the cutaneous signs of hypothyroidism?

• dull, dry, easily plucked hair, poor regrowth post-clipping, frictional alopecia (tail, neck, elbows)

• hyperpigmentation, seborrhea, and thickened skin

What skin lesions does acquired hypertrichosis in horses due to PPID cause?

prolonged anagen phase → failure to shed → long dense coat

What is superficial necrolytic dermatitis (hepatocutaneous syndrome)?

metabolic epidermal necrosis or diabetic dermatopathy caused by severe hepatic disease, diabetes mellitus, or glucagonoma

What is the pathogenesis of superficial necrolytic dermatitis?

hypoaminoacidemia → epidermal protein deficiency → necrosis of keratinocytes → crusted, erosive plaques on mucocutaneous junctions, paws, and pressure points; fissured pads cause lameness

What is protein calorie malnutrition?

severe protein deficiency due to inadequate dietary intake or secondary malabsorption/metabolic loss → hypoalbuminemia and edema → weight loss, muscle wasting, thin hair coat, poor shedding, dull fur, and alopecia

How does zinc deficiency affect the skin?

zinc is essential cofactor for >300 enzymes, crucial for cell division and keratinization → high phytate diets, excess calcium/copper/iron, or genetic malabsorption = deficiency → scaling, crusts, alopecia around mouth, eyes, ears, and pads

What are the two types of zinc deficiency?

type 1: hereditary malabsorption (nordic breeds)

type 2: nutritional deficiency (large breeds, high-calcium diets)

How does copper deficiencies cause skin lesions?

copper is a cofactor for tyrosinase, key in melanin synthesis → deficiency = coat color fading, “spectacle” hypopigmentation around eyes, and weak wool

How does selenium toxicosis cause skin lesions?

excess supplementation or ingestion of seleniferous plants → acute: mutlisystemic illness; chronic: hair loss, brittle mane/tail, deformed hooves, lameness, “alkali disease” → hoof cracking, hoof wall ridges, poor horn structure

What is plasma cell pododermatitis in cats?

immune-mediated, often with hypergammaglobulinemia, dermatitis associated with plasmacytic stomatitis and glomerulonephritis → swollen, soft paw pads with linear white striae

What is papillomatous digital dermatitis (bovine hairy heel wart)?

highly contagious bacterial dermatitis in dairy cattle, often linked to wet, unhygienic conditions → painful, foul-smelling ulcerated plaques near the heel bulbs, progressing to wart-like papillary growths causing lameness and economic losses

What is contagious foot rot in cattle?

dichelobacter nodosus (also fusobacterium necrophoroum) infection causing interdigital erosions, ulcerations, exudate, and crust formation

What is proliferative pododermatitis (cankers) in horses?

chronic proliferative hyperplasia of frog horn tissue, often in draft horses → friable, bleeding, foul-smelling proliferations in the frog and sole

What is necrotizing pododermatitis (thrush) in horses?

black, malodorous necrosis of frog tissue; deep tissue involvement leads to lameness and swelling due to fusobacterium necrophorum in moist, unsanitary environments

What is equine pastern dermatitis (“grease heel, or scratches”)?

multifactorial dermatitis → erythema, exudation, crusting, ulceration, and lameness; chronic cases become verrucous and fissured → worsened by moisture, poor hygience, and feathered legs

What is chronic progressive lymphedema in draft horses?

lymphatic dysfunction and dermal elastin defects causing chronic edema, fibrosis, scaling, and nodular thickening of lower limbs

What is equine coronary band dystrophy?

chronic symmetrical disease of coronary border and chestnuts causing scaly, hyperkeratotic, erythematous coronary badns, crakcs, fissures, and hoof wall defects

calcinosis cutis

zinc-responsive dermatosis

selenium toxicosis

proliferative pododermatitis

necrotizing pododermatitis (thrush)

equine pastern dermatitis