TRICHOGRAM
WHEN DO I DO IT?
- In every patient with alopecia
- To look for broken hair tips when one suspects self-induced alopecia
- To determine if hairs are in anagen or telogen phase (the interpretation of ratios of telogen hairs to anagen hairs in dogs is breed and season-dependent and exact ratios have not been established)
- When dermatophytosis is suspected
- To identify dogs with color dilute haircoats
- As an alternative to a deep skin scraping when Demodex is suspected
WHAT CAN I FIND
- Broken off hair tips → caused by self-trauma
- Tapered hair tips → hair loss is caused by events within the follicle e.g. endocrine disorders or inflammation involving the hair follicle
- Hairs in anagen (growing) phase → roots of anagen hairs are rounded, curled, bent and often smooth and pigmented
- Hairs in telogen (resting) phase → roots of telogen hairs are lancet-shaped and lack pigmentation, although the base of the hair may show a roughened or brush-like edge
- The presence of numerous anagen phase hairs should decrease the suspicion for an endocrinopathy
- In the case of dermatophytosis, affected hairs are covered with spores and penetrated by hyphae
- Color dilution alopecia→ melanin is clumped in the hair shaft
What do I need?
- Forceps/hemostat or rubber covered clamp, mineral oil, slide, cover slip, microscope
How do I do it?
- Pluck a small number of hairs in a partially or completely alopecic area using forceps/clamp in direction of hair growth; hold the forceps/clamp close to the skin surface and grasp all hair shafts which emerge
- Put a drop of mineral oil onto a slide, place the hairs in parallel order on the mineral oil, separate them to evaluate roots and tips adequately
- Cover hairs with a cover slip and evaluate with the microscope
Tip
- Cover the tips of your forceps or clamp with rubber or silicon sleeves to avoid crushing or breaking the hair shafts.
- You can also use the trichogram technique to look for Demodex mites in affected areas that are difficult to scrape (e.g. close to the eye, pododermatitis). Ideally a 1-2 cm2 area will be plucked, the same area as with a skin scraping.
- You might find Demodex mites hanging on the hairs or sometimes hiding behind them. Only positive results are diagnostic.
- You can also find lice, Cheyletiella mites and their eggs.
abscess
A discrete swelling containing purulent material, typically in the subcutis
alopecia
Absence of hair from areas where it is normally present; may be due to folliculitis, abnormal follicle cycling, or self-trauma
alopecia (“moth-eaten”)
well-circumscribed, circular, patchy to coalescing alopecia, often associated with folliculitis
angioedema
Regional subcutaneous edema
annular
Ring-like arrangement of lesions
atrophy
Thinning of the skin or other tissues
bulla
Fluid-filled elevation of epidermis, >1cm
hemorrhagic bullae
Blood-filled elevation of epidermis, >1cm
comedo
dilated hair follicle filled with keratin, sebum
crust
Dried exudate and keratinous debris on skin surface
cyst
Nodule that is epithelial-lined and contains fluid or solid material.
depigmentation
Extensive loss of pigment
ecchymoses
Patches due to hemorrhage >1cm
epidermal collarettes
Circular scale or crust with erythema, associated with folliculitis or ruptured pustules or vesicles
erosion
Defect in epidermis that does not penetrate basement membrane. Histopathology may be needed to differentiate from ulcer.
erythema
Red appearance of skin due to inflammation, capillary congestion
eschar
Thick crust often related to necrosis, trauma, or thermal/chemical burn
excoriation
Erosions and/or ulcerations due to self-trauma
fissure
Excessive stratum corneum, confirmed via histopathology. This term is often used to describe the nasal planum and footpads.
fistula
Ulcer on skin surface that originates from and is contiguous with tracts extending into deeper, typically subcutaneous tissues
follicular casts
Accumulation of scale adherent to hair shaft
hyperkeratosis
Excessive stratum corneum, confirmed via histopathology. This term is often used to describe the nasal planum and footpads.
hyperpigmentation
Increased melanin in skin, often secondary to inflammation
hypopigmentation
Partial pigment loss
hypotrichosis
Lack of hair due to genetic factors or defects in embryogenesis.
leukoderma
Lack of cutaneous pigment
leukotrichia
Loss of hair pigment
lichenification
Thickening of the epidermis, often due to chronic inflammation resulting in exaggerated texture
macule
Flat lesion associated with color change <1cm
melanosis
Increased melanin in skin, may be secondary to inflammation.
miliary
Multifocal, papular, crusting dermatitis; a descriptive term, not a diagnosis
morbiliform
A erythematous, macular, papular rash; the erythematous macules are typically 2-10 mm in diameter with coalescence to form larger lesions in some areas
nodule
A solid elevation >1cm
onychodystrophy
Abnormal nail morphology due to nail bed infection, inflammation, or trauma; may include: Onychogryphosis, Onychomadesis, Onychorrhexis, Onychoschizia
onychogryphosis
Abnormal claw curvature; secondary to nail bed inflammation or trauma
onychomadesis
Claw sloughing due to nail bed inflammation or trauma
onychorrhexis
Claw fragmentation due to nail bed inflammation or trauma
onychoschizia
Claw splitting due to nail bed inflammation or trauma
papule
Solid elevation in skin ≤1cm
papules
Solid elevation in skin ≤1cm
paronychia
Inflammation of the nail fold
patch
Flat lesion associated with color change >1cm
petechiae
Small erythematous or violaceous lesions due to dermal bleeding
phlebectasia
Venous dilation; most commonly associated with hypercortisolism
plaques
Flat-topped elevation >1cm formed of coalescing papules or dermal infiltration
pustule
Raised epidermal infiltration of pus
reticulated
Net-like arrangement of lesions
scale
Accumulation of loose fragments of stratum corneum
scar
Fibrous tissue replacing damaged cutaneous and/or subcutaneous tissues
serpiginous
Undulating, serpentine (snake-like) arrangement of lesions
telangiectasia
Permanent enlargement of vessels resulting in a red or violet lesion (rare)
ulcer
A defect in epidermis that penetrates the basement membrane. Histopathology may be needed to differentiate from an erosion.
urticaria
Wheals (steep-walled, circumscribed elevation in the skin due to edema ) due to hypersensitivity reaction
vesicle
Fluid-filled elevation of epidermis, <1cm
wheal
Steep-walled, circumscribed elevation in the skin due to edema