Paws, Claws, Horns, and Hooves (including diseases) Flashcards
Does nail development or follicular development occur first in humans?
Nails (slightly)
Mutations in ___ lead affect nail development and lead to syndromes such as ankyloblepharon, ectodermal dysplasia, cleft lip/palate, and ectrodactyly?
p63
What is thought to be important for dorsal limb patterning and therefore nail growth?
Wnt7
What is the primary homeodomain-containing gene that is important for development of follicles and nails?
Hoxc13
Which growth factor that is important for hair follicle development is not important for nail growth?
Shh
What are LMX1b and MSX1 important for?
Development of nails, eyes, limbs, and neurons
What are the basic functions of claws?
prehensile, locomotor, offensive and defensive mechanisms
What are the basic functions of foot pads?
shock absorbing, protection
What are the basic functions of horns/antlers?
defense, sexual attraction
Anonychia
Absence of claws (usually congenital)
Brachyonychia
Short claws
Leukonychia
Whitening of claws (suggestive of vitiligo when seen alone)
Macronychia
Unusually large claws
Micronychia
Unusually small claws, often shorter or narrower
Onychalgia
Claw pain
Onychatrophia
Atrophy or wasting away of claws; sometimes sequel to onychomadesis
Onychauxis (hyperonychia)
Simple hypertrophy of claws
Onychiitis (onychia)
Inflammation somewhere in the claw unit
Onychocryptosis (onyxis)
Ingrown claw
Onychodystrophy
Abnormal claw formation
Onychogryphosis (onychogryposis)
Hypertrophy and abnormal curvature of the claws
Onycholysis
Separation of claw structure at distal attachment and progressing proximally
Onychomadesis (onychoptosis)
Sloughing of claws
Onychomalacia (hapalonychia)
Softening of claws
Onychomycosis
Fungal infection of claws
Onychopathy (onychosis)
Disease or abnormality of claws
Onychorrhexis
Fragmentation and horizontal separation in lamellae at the free edge
Split then goes lengthways down the nail
Onychoschizia (onychoschisis)
Splitting of lamination of claws, usually beginning distally
Split then goes longitudinally along the nail
Pachyonychia
Thickening of claws
Paronychia (perionychia)
Inflammation or infection of claw folds
Platyonychia
Increased curvature of claws in long axis
Trachyonychia
Roughness of claws with brittleness and splitting; “sandpaper claws”
Briefly describe the claw of a carnivore
hard keratin modified skin encasing the distal phalax
consists of a wall and sole that is formed from soft horn linking with the lateral margins of the wall
What is the wall of the claw?
exterior portion of claw, shape of wall mimics curved ungual process of distal phalanx
What is the corium of the claw?
part of the dermis that covers P3; is composed of dense, irregular connective tissue; connects wall to distal phalanx; contains germinal cells to create keratinized cells; the “quick” – contains blood vessels, nerves, overlays periosteum of 3rd phalanx
What is the ungual process?
curved bony projection of distal phalanx in center of claw
What is the sole of the claw?
covers ventral surface of ungual process
What are the regions of the claw plate?
stratum externum, stratum medium, stratum intermedium
What is the claw fold?
dorsal area where haired skin meets claw; histopath features of normal skin
What do cats use to retract and extend their claws?
Digital flexor tendon, digital extensor tendon, dorsal elastic ligaments, forearm muscles
1- claw fold
2- dermis/corium
3- digital pad
7- limiting furrow (separates the digital pad from the sole)
9- middle phalanx
10- sole
11- wall
2- dermis/corium
4- distal phalanx
5- epidermis/digital pad
7- limiting furrow (separates the digital pad from the sole)
8- merocrine sweat gland
10- sole
2- dermis/corium
4- distal phalanx
6- laminae
10- sole
11- wall
Describe the histopathologic features of SLO
Unknown mechanism with hydropic and interface dermatitis
German Shepherd, Rottweiler, Gordon Setters
Young to middle aged
Dry, brittle, cracked claws
Bx: dorsal > ventral nailbed; P3 amputation
DDx.: immune-mediated, leishmaniasis, SLE, food allergy, drug reaction, idiopathic antibiotic-responsive disease
Describe subungual keratocanthomas?
Benign neoplasm of nailbed epithelium (dogs, cats)
Amputation is curative
Cup-/inverted funnel-shaped
Large squamous epithelial cells in broad trabeculae
No granular cell layer => amorphous keratin + parakeratotic cells
NO bone invasion!
DDx.: SCC (asymmetrical, desmoplasia, atypia, infiltrative, invasion of bone)
Subungual keratoacanthoma
Describe subungual SCC
Malignant neoplasm of nailbed epithelium
Giant Schnauzer, Gordon settern, briard, Kerry blue terrier, rottweiler, standard poodle
Single or multiple digits (forelimb > hindlimb)
Nail loss, infection, P3 destruction
Occasional mets of regional LNs and lungs
(↑ met potential than cutaneous SCC)
Describe feline plasma cell pododermatitis
Aka “pillow foot”
Young kitties
Likely immuno-mediated
Some also have plasma cell stomatitis, immune-mediated glomerulonephritis, or renal amyloidosis
50% cases are FIV+
Multiple feet (↑metacarpal & metatarsal pads)
↑ plasma cells (superficial and deep often including adipose), Mott cells (Russell bodies), ulcers
Subungual melanoma
How many germinal centers does the claw have?
4 (at least)
Where does the most growth in the claw come from?
dorsal surface at ungual crest creating thicker dorsal portion and
curves the claw ventrally
What is the principle germinative region of the claw?
- in the bony ungual groove
- makes most of the outer claw plate (SE and SM)
- if destroyed it will result in permanent onychodystrophy
**Important in SLO and vasculitis!!
What is the terminal matrix of the claw?
- Makes SI cells
- provides thickening to inner portions of claw plate beyond ungual groove
- distal expansion of SI fills gap between claw plate and ungual groove
What is the proliferative claw matrix?
basal and lower spinous layer (keratogenous zone) at proximal
end of claw is actively involved in producing claw plate
Where is the softest keratin found in the claw?
Sole (K5, 6, 14, 16, 17)
What keratins are found in the stratum externum of the claw?
K25-38; K71-K86
Where are the hardest keratins found the claw?
Claw plate
What keratins are found in the stratum medium of the claw?
K6, 16/17?
What are the primary sections of the claw?
sole (ventral)
claw plate made of 2 laterally compressed walls (axial and abaxial) and central dorsal ridge
What is the nail unit
the claw, the coronary band distal to the sole, and the underlying P3