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Lesion types + clinico-pathological correction - Coggle Diagram
Lesion types + clinico-pathological correction
Atrophic diseases
often hormonal
miniaturisation or cycle arrest (all follicles in telogen phase)
hair follicles present with alopecia--> absence of hair in an area where it is normally present (complete or partial)
hypotrichosis= partial hair loss
hyperadrenocorticism--> high levels of cortisol lead to hair follicles being in a prolonged stage of arrest
uncommon
Dysplastic diseases
uncommon
hair follicle or fibre is malformed or distorted
e.g. sphynx cat: congenital alopecia associated with mutation in KRT71, which codes for an inner root sheath keratin
"saddleback" in curly coated retriever with follicular dysplasia
Inflammatory diseases (infections + infestations)
follicle becomes target of inflammation due to bugs
common
luminal folliculitis: common, cells chase infection/infestation (usually reflects pyoderma, dermatophytosis or demodicosis)
mural folliculitis: uncommon, cells gather in sheath of follicle
bulbitis: rare, cells in hair matrix/dermal papilla e.g alopecia areata
perifolliculitis: cells around vascular plexus adjacent to follicle
dermatophytosis: folliculitis + furunculosis, fungal spores on hair
demodicosis: "red mange", demodex mites, bulldogs prone to juvenile onset generalised demodicosis (genetic defect, failure of immune system)
furunculosis= inflamm + destruction of follicle, e.g. pyoderma + perianal fistulae
Inflammatory diseases (immune/cytotoxic assaults)
rare
follicle targeted by inflammation due to immune dysregulation (often mural)
bulbitis= classical histopathological feature of alopecia areata
Matrix/melanocyte abnormalities
e.g. colour dilution in fawn Doberman: a type of follicular dysplasia associated with melanocyte dysfunction
Comedo
dilated hair follicle plugged with keratinous/sebaceous debris
blackheads, whiteheads
Follicular cast
accumulation of keratinous debris around hair shaft
seen in demodicosis, primary defects of cornification and sebaceous adenitis (scales around hairs)
Wheals
urticaria: wheals 'pit' on pressure due to dermal oedema
common
Papule = solid palpable skin elevation < 1cm (d)
Plaque- larger, flat-topped elevation caused by extension or coalition of papules
Nodules= solid lesions (on palpation) >1cm (d)
panniculitis is usually nodular: foreign body reaction, idiopathic sterile, systemically or traumatically implanted infection, nutritional
Pustules= discrete elevation of epidermis containing pus
intraepidermal pustular dermatitis: neutrophilic (pyoderma), eosinophilic (ectoparasite infestation, hypersensitivity)
Abscess= demarcated dermal or subcutaneous accumulation of pus
Vesicles = circumscribed elevations of the skin <1cm (d), containing clear fluid
Bullae= blister
Erosions + ulcers are flat skin lesions which have a break in the continuity of the epidermis
basement membrane intact= erosion
basement mebrane breached, exposing dermis= ulcer
excoriation= caused by patient scratching, biting or rubbing
Macule = flat circumscribed area of change in skin colour <1cm (d), Patch= >1cm (d)
Scale= accumulation of loose cornified fragments of the stratum corneum
Crust= presence of dried exudate on skin surface (serum, blood, pus)
Configuration of skin lesions
single/grouped
circular
polycyclic
annular (ring-like)
arciform
serpiginous (snake-like)
linear
