28.

Pathologic keratinization

9th October 2019

Stratum lucidum (clear layer)

(Odland granules)

steps of keratinisation

• Cytoplasmic filaments

– praekeratin

• Keratohyalin granula

– autophagocytosis

– granula formation

• Odland’s granules

– granula bordered by membranes

regulation of epidermal cell

differentiation• cytokines

– e.g. growth factors, interleukins, TNF

• hormones– e.g. vit D3, cortisol

• nutritional factors– protein uptake, Zn, Cu, vit.s A and B

• autoregulation (autocrine function)

disturbances of keratinisation

• frequently in the cornified epithelium– skin

– modified appendices of the epithelium• hoof, horn …

– forestomachs

– esophagus (carnivores < su < eq < Ru)

– pars oesophagica• e.g. rat, horse

– mouth cavity• different sites according to the species

• back of the tongue

• also in non-cornified epithelium– but data are scarce

Disturbances in keratinisation

• 1) Hypokeratosis• rare

• wasting diseases

• starvation

• 2) Hyperkeratosis

• 3) Parakeratosis

• 4) Dyskeratosis• keratinisation in the str. spinosum

Disturbances in keratinisation

Forms

• Hyperkeratosis (2)– thickening of the str. corneum

– cornification process completed• (cell nucleus dissolved)

• Parakeratosis (3) – thickening of the str. corneum

– incomplete cornification process• (cell nucleus retained)

• Local (A) – generalized (B)

• Congenital - Aquired

• intense epithelial hyperplasia

• intense keratinisation

in the str. corneum

• cutaneous horn

2/A) Local hyperkeratosis

• mechanical cause

– callus, tyloma

• chronic inflammation or circulatory disturbance

– pachydermia

• malformation (hamartia)

– cutaneous horn (cornu cutaneum)

• trophoneurotic disturbance

– „hard pad” (chronic canine distemper)

2/A) Local hyperkeratosis

Hard pad disease

2/B) Generalized hyperkeratosis

• A-avitaminosis or anti vitamin A effect

– nutritive

• biotin-deficiency

– common in turkey

• toxical floor (asphalt)

– piglets

• intoxication - chlorinated naphthalenes

– cattle’s X-disease (1950’s)

• primary seborrhea

– cocker spaniel, WHWT, persian cat etc.

• ichthyosis congenita (disease group)

– recessive genetical (lethal) factor (cattle, dog)

• nutritive: vit. A deficiency

• toxicosis: chlorinated naphthalenes

Biotin deficiency

Ichthyosis congenita - calves

• complete orthokeratotic

hyperkeratosis

• more forms

• severe complications

Ichthyosis congenita - dogs

• complete orthokeratotic

hyperkeratosis

• more forms, few breeds

Hyperkeratosis in the rumen

3) Parakeratosis

• cornyfied layer thicker

• nuclei still present close

to the surface

– skin edema

– Zn-deficiency

• pigs/dogs skin

– chronic inflammation

• skin, rumen etc.

3) Parakeratosis

• macroscopic lesions

• SKIN– dry, laminar structure and crumbling

– Zn-deficiency• consistency: greasy (sebaceous gland hyperfunction)

• colour: dark brownish after drying out

– acanthosis nigricans/ AN-like disorders• consistency: dry, velvety touch

• colour: melanin hyperpigmentation

• RUMEN– papillae stick together → willow-leaf-like apperiance

– maceration → „greasy” consistence of cornified layer

3) Parakeratosis

• Lack of granules

• Retained nuclei of epithelial cells

in str. corneum

Hyper- and parakeratosis

• disturbance of the keratinisation of the rumen

epithelium (hyper- and parakeratosis) results in a

specific disease in cattle

hyper- and parakeratosis of the rumen

liver abscessation

hyper- and parakeratosis-rumenitis

liver abscess complex

hyper- and parakeratosis-rumenitis

liver abscess complex

hyper- and parakeratosis of the rumen,

liver abscessation

• constant (pathologic) acidic pH

• hyper- and parakeratosis - locus minoris resistentiae

• colonising pathogenic bacteria

• chronic inflammation

• bacteria in the propria - v. portae - liver

• purulent, ichorous and/or necrotising inflammation

Parakeratosis - liver abscessation

syndrome

4) Dyskeratosis

• keratinisation starts in the

str. spinosum

• prematured, apoptotic cells

• rare

• primary– congenital (polled Hereford calves)

• secondary