Paws, Claws, Horns, and Hooves (including diseases) Flashcards
1
Q
Does nail development or follicular development occur first in humans?
A
Nails (slightly)
2
Q
Mutations in ___ lead affect nail development and lead to syndromes such as ankyloblepharon, ectodermal dysplasia, cleft lip/palate, and ectrodactyly?
A
p63
3
Q
What is thought to be important for dorsal limb patterning and therefore nail growth?
A
Wnt7
4
Q
What is the primary homeodomain-containing gene that is important for development of follicles and nails?
A
Hoxc13
5
Q
Which growth factor that is important for hair follicle development is not important for nail growth?
A
Shh
6
Q
What are LMX1b and MSX1 important for?
A
Development of nails, eyes, limbs, and neurons
7
Q
What are the basic functions of claws?
A
prehensile, locomotor, offensive and defensive mechanisms
8
Q
What are the basic functions of foot pads?
A
shock absorbing, protection
9
Q
What are the basic functions of horns/antlers?
A
defense, sexual attraction
10
Q
Anonychia
A
Absence of claws (usually congenital)
11
Q
Brachyonychia
A
Short claws
12
Q
Leukonychia
A
Whitening of claws (suggestive of vitiligo when seen alone)
13
Q
Macronychia
A
Unusually large claws
14
Q
Micronychia
A
Unusually small claws, often shorter or narrower
15
Q
Onychalgia
A
Claw pain
16
Q
Onychatrophia
A
Atrophy or wasting away of claws; sometimes sequel to onychomadesis
17
Q
Onychauxis (hyperonychia)
A
Simple hypertrophy of claws
18
Q
Onychiitis (onychia)
A
Inflammation somewhere in the claw unit
19
Q
Onychocryptosis (onyxis)
A
Ingrown claw
20
Q
Onychodystrophy
A
Abnormal claw formation
21
Q
Onychogryphosis (onychogryposis)
A
Hypertrophy and abnormal curvature of the claws
22
Q
Onycholysis
A
Separation of claw structure at distal attachment and progressing proximally
23
Q
Onychomadesis (onychoptosis)
A
Sloughing of claws
24
Q
Onychomalacia (hapalonychia)
A
Softening of claws
25
Onychomycosis
Fungal infection of claws
26
Onychopathy (onychosis)
Disease or abnormality of claws
27
Onychorrhexis
Fragmentation and horizontal separation in lamellae at the free edge
Split then goes lengthways down the nail
28
Onychoschizia (onychoschisis)
Splitting of lamination of claws, usually beginning distally
Split then goes longitudinally along the nail
29
Pachyonychia
Thickening of claws
30
Paronychia (perionychia)
Inflammation or infection of claw folds
31
Platyonychia
Increased curvature of claws in long axis
32
Trachyonychia
Roughness of claws with brittleness and splitting; “sandpaper claws”
33
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
34
What is the wall of the claw?
exterior portion of claw, shape of wall mimics curved ungual process of distal phalanx
35
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
36
What is the ungual process?
curved bony projection of distal phalanx in center of claw
37
What is the sole of the claw?
covers ventral surface of ungual process
38
What are the regions of the claw plate?
stratum externum, stratum medium, stratum intermedium
39
What is the claw fold?
dorsal area where haired skin meets claw; histopath features of normal skin
40
What do cats use to retract and extend their claws?
Digital flexor tendon, digital extensor tendon, dorsal elastic ligaments, forearm muscles
41
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
42
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
43
2- dermis/corium
4- distal phalanx
6- laminae
10- sole
11- wall
44
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
45
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)
46
Subungual keratoacanthoma
47
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)
48
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
49
Subungual melanoma
50
How many germinal centers does the claw have?
4 (at least)
51
Where does the most growth in the claw come from?
dorsal surface at ungual crest creating thicker dorsal portion and
curves the claw ventrally
52
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!!
53
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
54
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
55
Where is the softest keratin found in the claw?
Sole (K5, 6, 14, 16, 17)
56
What keratins are found in the stratum externum of the claw?
K25-38; K71-K86
57
Where are the hardest keratins found the claw?
Claw plate
58
What keratins are found in the stratum medium of the claw?
K6, 16/17?
59
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
60
What is the nail unit
the claw, the coronary band distal to the sole, and the underlying P3
61
What are the 2 slippage zones of the claw?
- Inner claw bed (K17)
-B/W inner of outer claw sheath (K6, 77, 16, 17)
62
What keratins are expressed in the stratum internum of the claw?
K25-38; K71-K86
63
What is the stratum tectorium?
a thin protected outer layer of the proximal claw
64
Describe the histopathology of the dog claw.
- Dermis has a papillate structure
- inner surface lacks hair and glands
- claw matrix has epidermal pegs with corresponding dermal papillae
- epidermis is mostly stratum corneum
- few to numerous intranuclear vacuoles are found in the stratum spinosum
- clefts at the DEJ are present most commonly in dorsal matrix
- sole has stratum granulosum and lucidum but rest lacks granulosum
65
Describe the histopathology of the cat claw.
- clefts are seen at DEJ and other levels
- intracytoplasmic vacuoles are present in keratinocytes
- pseudospongiosis
- about 2-3 apoptotic keratonocytes/hpf in dorsal and ventral matrices
66
Where are keratinocytes most active in the claw?
dorsal central ridge and coronary band
67
What are the primary minerals in claws?
Contain calcium, potassium, sodium and phosphorus (less zinc)
- Dogs with onychomadesis have increased CA, K, Na, P but less Fe, Mg, Mn
- German Shepherd dogs overrepresented
68
What is the average growth per week of a dog claw?
Beagle dogs – 0.7 to 2.1mm per week
- Increases in first 3 years of life, then decreases about 50% by 15 years of age
- Breed, housing, diet, exercise likely contribute
69
Describe the chemical properties of nails
hard keratins in an amorphous matrix composed of cysteine rich, high sulfur proteins
70
What is the primary function of foot pads?
protect against mechanical trauma to paw and absorb shock
71
What is the digital cushion?
The base of the footpad
SQ adipose tissue with reticular, collagenous and elastic fibers
72
What provokes atrichial sweating?
primarily cholinergic stimuli, less adrenergic
73
What blocks atrichial sweating?
atropine (decreases all secretions)
74
Describe the primary histopathologic difference between cat and dog pads
- surface is smooth in cats but rough in dogs due to conical papillae
which are heavily keratinized
- rete ridges present in both
75
Describe the epidermis of the footpad.
o Stratum basale – basal cells, single layer on BMZ
o Stratum spinosum – 10-15 layers, diamond or dome shaped cells (thick)
o Stratum granulosum – 4-7 layers, flattened, basophilic keratohyaline granules in cytoplasm
o Stratum lucidum – keratinized layer of dead cells, shiny acidophilic layer of homogenous substance with refractile droplets (eleidin!)
Locations of this layer in the dog? Footpad, horse hoof
o Stratum corneum – thick, keratinized, non-nucleated material, thicker than all other cell layers COMBINED
76
Where can rete ridges be found?
footpad, nasal planum, scrotum
77
Feline paw pad
1. dermis, papillary layer
2. dermis, reticular layer
3. digital cushion
4. duct of a sweat gland
5. epidermis
78
Disease of the footpad that cause crusting and fissuring
Canine Distemper
Pelodera dermatitis
Hookworm
Leishmaniasis
Hepatocutaneous syndrome
Calcinosis circumscripta
Zn responsive
Pulmonary adenocarcinoma (lung digit)
Paraneoplastic alopecia (cat)
Lethal acrodermatitis of white bull terriers
PF
78
Describe the dermis of the footpad
Bulk of the pad
Dense connective tissue
- Collagen and elastic fibers interspersed in the adipose tissue
- Eccrine sweat glands and lamellar corpuscles embedded
- Dense connective tissue under epidermis forms conical dermal cores that the epidermal papillae fit into (2’ dermal papillae)
79
Diseases of the footpad with keratinous proliferation
Nasodigital hyperkeratosis
Distemper
Familial palmoplantar hyperkeratosis
80
Diseases of the footpad that cause ulceration/sloughing
Vasculitis of the GSD
Tyrosinemia
Focal metatarsal fistulae of GSD
Vasculitis of the JRT
Plasma cell pododermatitis
PV
EB
81
What is important to know about vacuoles on histopathology of a claw?
- may be artifact, these samples are difficult to process
82
What are asymmetrical diseases of claws?
- trauma
- infection
- neoplasia
83
What diseases should you think of when paronychia is also involved?
- infection
- PF
- cryoglobulinemia
- drug rxn
- vasculitis
84
What diseases should you think of when only the claw is symmetrically affected?
- SLO
- lupus erythematosus
- subepidermal bullous disease
- pemphigus vulgaris
85
Solar surface of the hoof.
1 = Bulb of the heel
2 = angle of wall
3 = bar
4 = white zone (line)
5 = stratum medium
6 = epidermal laminae
7 = body of sole
= apex of frog
9 = crus of sole
10 = collateral groove
11 = central sulcus of frog.
86
Describe the growth of the hoof
- grows from epidermis covering coronary dermis
- consists of horn tubules in intratubular horn
87
What are the parts of the hoof wall?
Coronary groove
Stratum externum
* Stratum medium (pigmented vs nonpigmented portions)
* Stratum internum (primary epidermal laminae)
*most important
88
What is the stratum externum of the hoof?
Thin layer of tubular and intertubular horn that originates from germinal layer of the epidermis of the periople
AKA peripolic epidermis
helps to retain moisture but mostly gets worn off
89
What is the peripole of the hoof?
- Part of the stratum externum
- ring of soft, nonpigmented tubular horn a few mm thick around the coronet
- dries into thin glossy layer distally
- Widens toward the back of the foot to form broad bulb/heel, blends with base of frog
- Produced over the peripolic dermis that is continuous with dermis of skin proximally and coronary corium distally
90
What is the stratum medium of the hoof?
AKA coronary epidermis
Mostly pigmented
Tubular and intertubular “hard” horn
- Rods from the horny tubules orient parallel to outer surface of hoof
MAIN supportive structure of wall
This helps shock absorb on hard surface
91
What is the stratum internum of the hoof?
AKA laminar epidermis
- composed of about ~600 (insensitive) laminae that interdigitate with the (sensitive) laminar dermis
- Primary laminae are vertically oriented and extend inward from SM
- Secondary laminae project from 1’ at acute angle (~200 per each primary)
- are composed of stratum germinativum (stratum basale and spinosum)
92
Why do the laminae of the stratum internum interdigitate with the laminae of the corium?
create epidermal dermal association
anchors to underlying connective tissue
sensitivity
93
What is the sole of the hoof?
Tubular and intertubular horn, can be peeled off in flakes
Corium of sole bears long papillae
Epidermal covering of the dermal papillae give rise to tubular horn of sole
94
What is the frog of the hoof?
Palmar plantar surface of hoof (kind of like a footpad)
Poor quality tubular horn
Branched coiled merocrine sweat glands
Kept soft by fatty secretions of the glands under digital cushion
95
What is the white line (zona alba) of the hoof?
Junction between sole and wall
Nonpigmented (poor quality) tubular horn
On the basal surface of the hoof between the surface of the wall and edge of the sole
96
Where is the primary site of thrush in horses?
Paracuneal grooves
97
What are the parts of the hoof corium?
- perioplic dermis (top at coronet)
- coronary dermis (wider elevation at coronet due to underlying cushion)
- laminar dermis
- dermis of the sole
- dermis of the frog
98
Top (developing hoof wall from horse fetus)
Bottom two (hoof, laminar region)
1. basal cell
2. blood vessel
3. P3
4. Dermal lamina, primary
5. Dermal lamina, secondary
6. Epidermal lamina, primary
7. Epidermal lamina, secondary
8. horn tubule
9. laminar dermis
10. stratum medium
99
What is the hoof corium?
a highly vascular dermis that underlies the hoof wall and consists of a dense matrix of tough connective tissue (mostly collagen 1) containing a network of arteries, veins, capillaries, and sensory vasomotor nerves
99
What are the functions of the hoof corium?
Provide nourishment to hoof and connect hoof to bone
100
What part of the corium does not have papillae that fit tightly into the holes of the adjacent hoof?
lamellar corium (has primary and secondary lamellae)
101
Where is the subcutis thickest in hooves?
beneath the coronary dermis - coronary cushion
beneath the frog- digital cushion
102
What should strike the ground first in an unshod horse?
The frog and digital cushion
103
Describe hoof keratin
hard keratin like hair (higher numbers)
hoof wall is rich in disulfide bonds due to cysteine which makes it strong
frog and white line are rich in sulfhydryl groups which is less strong but more elastic
104
How does the BMZ of the hoof vary from elsewhere?
- High density of lamina densa extensions and anchoring filaments around the tips
of secondary epidermal lamella
- Laminin and collagen IV are of vital importance and are destroyed with acute
laminitis
105
What is the role of MMPs in the hoof?
MMPs 2 and 9 are responsible for remodeling various classes of epidermal cells in the
BMZ, secondary epidermal lamellae and primary epidermal lamella
106
What upregulates MMP 2 and 9?
- they are upregulated by IL-1 and TNFa
107
What happens when there is too much MMP production in the hoof?
Uncontrolled excessive MMPs results in disorganized epidermal cells of the secondary epidermal lamella, separation of basal cells from BMZ, and lysis of BMZ so
laminitis develops
(attack laminin-5, collagen XVII which are components of hemidesmosomes too)
108
What are some traumatic diseases of the hoof?
Subsolar abscesses, navicular bone or third phalanx, side bones fracture
Frostbite results in necrosis and sloughing at coronet
Immersion foot (standing in cold water for days): pain, edema, erythema and necrosis of areas submerged
Wound of coronary band resulting in weird hoof growth
109
How do ruminant and porcine hooves differ from horses?
- there are 2
- lamellar epidermis only has primary laminae (but more of them)
- papillary orientation of the sole is more cranial
- more zones of the epidermis are apparent
- do not have frogs or bars
- Pigs have carpal glands to mark territory and II and V are fully formed dewclaws, do not bear weight
110
What is laminitis?
Degeneration of interface between epidermal and dermal lamina resulting in rotation of P3 ventrally
111
What causes laminitis?
endotoxemia (carb overload, sepsis, shock, diarrhea), steroids
112
What disappear from the basement membrane in laminitis?
Laminin (covers collagen IV) and collagen IV
113
What is thrush?
Anaerobic bacteria (can also be aerobic or fungal)
Typically affects the central frog or grooves adjacent to and in the middle the frog (collateral sulci)
114
What is white line disease?
Primarily affects stratum internum
Bacterial or fungal
115
What is the cornual process of the horn?
Bony projection at center of horn, grows from frontal bones of skull, ridged and porous
116
Describe the dermis of the horn
Covers corneal process like periosteum, papillated
117
Describe the epidermis of the horn
Covers dermis, produces the horn sheath/wall
118
What is the epiceras of the horn?
Softer outermost layer of epithelium produced by transitional, irregular epithelial strips at the base of the horn at transition from regular epidermis
Resembles periople of hoof
Gives horn glossy sheen
119
What is the horn sheath?
Modified stratum corneum, tubules formed over dermal papillae; runs lengthwise and held together by intertubular horn (produced by interpapillary regions of epidermis)
120
What is the horn wall?
Shell of tubules and tubular horn that grows from epithelium and covers the dermis over the cornual process
121
1. cornual diverticulum of the frontal sinus
2. cornual process
3. periosteum, dermis, and epidermis
4. horn tubules
122
Where are bovine horns located if present?
Temporally
123
Where are ovine/caprine horns located if present?
Parietal
124
What does polycerate mean?
having multiple horns
125
What are antlers?
NOT a true horn
not covered by keratinized epithelium
Structure grown as an extention of the skull and grow from bony pedicles in the lateral region of frontal bone, branch (horns never branch)
Shed and regrow each year
Males only, except caribou females
126
Which sheep loose and regrow horn sheath each year?
Pronghorn
127
Is intertubular horn or tubular horn in hooves more likely to fracture?
tubular (3x)
128
What is the eponychium?
Persistent layer of periderm over hooves in fetal ungulates
128
What are chestnuts and ergots of horses?
tubular and intertubular horn with a corium that is devoid of glands
considered vestiges of paw pads
128
Which bacteria are most likely to affect canine claws?
S. pseud, Nocardia, Actinomyces, Pseudomonas, Proteus (unknown source for this info)
128
Other than Malassezia, what is the most common organism associated with onychomycosis in dogs?
T. mentagrophytes
129
Other than Malassezia, what is the most common organism associated with onychomycosis in cats?
M. canis
130
Which neoplasias most commonly affect canine claws?
SCC
Melanoma
Keratoacanthoma
131
What parasites most commonly affect canine claws?
Pelodera strongyloides
Anyclostoma
Uncinaria (stenocephala)
132
What protozoa most commonly affect canine claws?
Leishmania
133
What systemic illnesses most commonly affect canine claws?
Hepatocutaneous
Zinc responsive
134
What is familial vasculopathy of GSDs?
Autosomal recessive
Paw pads are soft and swollen with variable depigmentation +/- ulcer, bridge of nose is swollen, ulcers on ear margins and tail tip
Are also pyrexic and lethargic with varying lymphadenopathy
Affects GSD puppies 4-10 wk old
Histopath shows nodular to diffuse lymphoplasmacytic dermatitis around degenerated collagen and altered vasculature
Treatment: if they make it through, they spontaneous recover at 5 to 6 months old with scarring
135
What breeds are most represented for familial/idiopathic footpad hyperkeratosis?
- Irish terriers (recessive)
- Kerry blue terriers
- Douges de Bordeaux
- Labs
- Goldens
- Mixes
* usually happens by 6 mo of age
136
What causes nasodigital hyperkeratosis?
Congenitohereditary OR coexist with other disorders, diseases and aging
Idiopathic is mostly in older dogs so probably a senile change
If nasal only:
- Congenital for Labrador retriever, DLE, PE, PF, cutaneous lymphoma
If pads only:
- Familial pad hyperkeratosis, papillomavirus, PF, weight bearing abnormality
137
What is tyrosinemia?
Similar to tyrosinemia type II in ppl and pseudodistemper in mink
- in ppl in autosomal recessive with 5 phenotypes
Reported in 7 wk GSD with conjunctivitis, small globes with cataracts, corneal granulation, and ulceration of nose, tongue, central footpad
Cause: cannot break down tyrosine --> inflammatory rxn to crystals in tissue
Diagnosis: high tyrosine in serum and urine
Histopathology: tyrosine crystals in tissue with surrounding pyogranulomatous inflammation and Splendore-hoeppli-like reaction
Treatment: try a low tyrosine and phenylalanine die but not great prognosis
138
Describe Raynaud's disease in dogs.
3 middle aged dogs reported
Onychalgia, onychogryphosis, intermittent acrocyanosis of multiple digits and
paws
Vasodilator isoxsuprine (1mg/kg/d PO) controlled disease
139
What is idiopathic onychodystrophy?
NOT due to onychomadesis
Diagnosed when multiple paws and claws affected and another cause cannot be
found
- may become secondarily infected
Older dogs
Cocker spaniels, dachshunds, Rhodesians, huskies, welsh terriers
Treatment: Gelatin and biotin, fatty acids, good quality high protein diet, pentoxifylline
140
What is idiopathic onychomadesis?
Reported as dz, most not biopsied so what is actually happening
GSD, whippet, English springer spaniel
Increased Ca, Na, K, P concentrations but low iron, manganese, magnesium
Claws lost without having prior onycholysis – separates this from SLO
Treated like SLO
141
Symmetric onychomadesis in Norwegian, Gordon, and English Setters
*Publication from 2008
Acute onset with loss of one or several claw plates then shedding of most others
Otherwise healthy, Usually between age 2-7
No correlation with vaccination
8 dogs total, 6 had affected siblings
Histopath- hydopic degeneration, pigmentary incontinence, lymphoplasmacytic
lichenoid interface dermatitis (so how is this different from variants of SLO?)
Tx- fatty acid supplementation, tetracycline/doxycycline with niacinamide,
steroids
142
What are the causes of plasma cell pododermatitis?
Unknown, suspect immune-mediated or structural
o Often (40-60%) FIV + and hyperglobulinemic
o May be antigenic stimulation, may be seasonally exacerbated
143
What are the clinical features of plasma cell pododermatitis?
Any age, often DSH
Soft swelling of multiple foot pads which may deflate or ulcerate (single pad rare)
Lightly pigmented pad may look blue
Lameness
Some have plasma cell stomatitis and plaques on the palatine arches (minority)
May have lymphadopathy, pyrexia, lethargy can be seen, rarely glomerulonephritis,
plasma cell rhinitis
144
How do you treat plasma cell pododermatitis?
Test them for FIV!
Doxycycline 10mg/kg QD with water up to 10 weeks resolves 1/3rd, improves 80%
Can resolve spontaneously
Steroids if no response to doxy and very painful/affected
Cyclosporine 7mg/kg QD
Potentially surgical excision as it is effective in reports with no recurrence
145
What is the structure of the avian beak?
bony structure covered in a keratinized, horny material known as the rhamphotheca
- rhampotheca has calcium phosphate and hydroxyapatite
dermis is under the rhampotheca
- attaches it to underlying periosteum
large number of nerve endings
- especially from trigeminal
