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