表皮の掻爬試験
いつ行うか？
- 皮膚搔痒感または鱗状皮膚のある患者すべてに実施
何を見つけるか？
- Cheyletiella属（ツメダニ）、Scabies属（ヒゼンダニ）、ネコショウヒゼンダニ、ミミヒゼンダニ, またはシラミ→これらのダニまたはその卵が1個でも見つかれば、診断に使用できる。
- 毛幹に付着する皮膚糸状菌胞子
何が必要か？
- スライド、カバーガラス、メス刃、ミネラルオイル、顕微鏡
どのように行うか？
- 必要に応じて、鱗屑および痂皮がはがれないよう、罹患部位の被毛を2～3 mm残してそっと刈り取る。ミネラルオイルをメス刃に垂らす。皮膚にも数滴、直接垂らす。
- このオイルをメス刃でそっと擦り取り、生検材料を1枚以上のスライドに乗せる。ダニは、表層上または表層内で生きている。表皮の掻爬試験では血を滲ませるまで掻爬する必要はない。
- コンデンサを下げた顕微鏡でスライドを観察する。
ヒント
- 探しているダニがもっとも見つかりそうな領域をサンプリングする。ヒゼンダニ属では、耳の縁、前肢関節、後肢関節、腹部である。
- ダニは見つけづらい可能性がある。剃毛した表面領域が広いほど、結果が陽性となる確率が高くなる。結果が陰性である場合、およびヒゼンダニ属の寄生が依然として疑われる場合、次に行うべきステップとしてもっとも確実なものは6週間の診断的治療試験である。
- Cheyletiella属ダニ（ツメダニ）またはシラミを採取するのに粘着テープの使用を好む医師もいる。この手技では、粘着テープを落屑のある部位に複数箇所押しつけるほか、毛幹にこすりつける。この粘着テープをガラススライドに直接のせ、ミネラルオイルを1滴垂らし、コンデンサを下げて再び観察する。
- 皮膚糸状菌症が疑われる場合には、被毛、表皮落屑、壊死組織片を「固定」または「保持」するのに必要最小量のオイルの使用にとどめる。
abscess
A discrete swelling containing purulent material, typically in the subcutis
Perianal abscess in a dog
alopecia
Absence of hair from areas where it is normally present; may be due to folliculitis, abnormal follicle cycling, or self-trauma
Extensive alopecia secondary to cutaneous epitheliotropic lymphoma
alopecia (“moth-eaten”)
well-circumscribed, circular, patchy to coalescing alopecia, often associated with folliculitis
“Moth-eaten” alopecia secondary to superficial bacterial folliculitis
hemorrhagic bullae
Blood-filled elevation of epidermis, >1cm
Interdigital hemorrhagic bulla in a dog with deep pyoderma and furunculosis
comedo
dilated hair follicle filled with keratin, sebum
Comedones on the ventral abdomen of a dog with hypercortisolism
crust
Dried exudate and keratinous debris on skin surface
Multifocal crusts due to pemphigus foliaceus
epidermal collarettes
Circular scale or crust with erythema, associated with folliculitis or ruptured pustules or vesicles
Epidermal collarettes in a dog with Staphylococcus superficial bacterial folliculitis
erosion
Defect in epidermis that does not penetrate basement membrane. Histopathology may be needed to differentiate from ulcer.
Erosions in a dog with vasculitis
erythema
Red appearance of skin due to inflammation, capillary congestion
Erythema in a dog with cutaneous drug eruption
eschar
Thick crust often related to necrosis, trauma, or thermal/chemical burn
Eschar from physical trauma
excoriation
Erosions and/or ulcerations due to self-trauma
Excoriations in a cat with atopic dermatitis
fissure
Excessive stratum corneum, confirmed via histopathology. This term is often used to describe the nasal planum and footpads.
Fissures of the footpads in a dog with superficial necrolytic dermatitis
fistula
Ulcer on skin surface that originates from and is contiguous with tracts extending into deeper, typically subcutaneous tissues
Perianal fistulas in a dog
follicular casts
Accumulation of scale adherent to hair shaft
Follicular casts surrounding hairs from a dog with hypothyroidism
hyperkeratosis
Excessive stratum corneum, confirmed via histopathology. This term is often used to describe the nasal planum and footpads.
Idiopathic hyperkeratosis of the nasal planum (left) and footpads (right)
hyperpigmentation
Increased melanin in skin, often secondary to inflammation
Inflammatory lesions (left) resulting in post-inflammatory hyperpigmentation (right)
hypotrichosis
Lack of hair due to genetic factors or defects in embryogenesis.
Congenital hypotrichosis in chocolate Labrador puppies.
lichenification
Thickening of the epidermis, often due to chronic inflammation resulting in exaggerated texture
Lichenification of skin in a dog with chronic atopic dermatitis and Malassezia dermatitis
macule
Flat lesion associated with color change <1cm
Pigmented macule (left) Erythematous macule (right)
melanosis
Increased melanin in skin, may be secondary to inflammation.
Post inflammatory hyperpigmentation of this dog’s thigh
miliary
Multifocal, papular, crusting dermatitis; a descriptive term, not a diagnosis
Miliary dermatitis in a flea allergic cat
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
Morbiliform eruptions in a dog with a cutaneous drug reaction
onychodystrophy
Abnormal nail morphology due to nail bed infection, inflammation, or trauma; may include: Onychogryphosis, Onychomadesis, Onychorrhexis, Onychoschizia
Onychodystrophy in dog with chronic allergies
onychogryphosis
Abnormal claw curvature; secondary to nail bed inflammation or trauma
Onychogryphosis in a dog with symmetric lupoid onychodystrophy
onychomadesis
Claw sloughing due to nail bed inflammation or trauma
Onychomadesis in a dog with symmetric lupoid onychodystrophy
onychorrhexis
Claw fragmentation due to nail bed inflammation or trauma
Onychorrhexis in a dog with symmetric lupoid onychodystrophy
onychoschizia
Claw splitting due to nail bed inflammation or trauma
Onychoschizia in a dog with symmetric lupoid onychodystrophy
patch
Flat lesion associated with color change >1cm
Hypopigmented patch (left), erythematous patch (right)
petechiae
Small erythematous or violaceous lesions due to dermal bleeding
Petechiae in a dog with cutaneous vasculitis
phlebectasia
Venous dilation; most commonly associated with hypercortisolism
Phlebectasia and cutaneous atrophy due to hypercortisolism in a dog
plaques
Flat-topped elevation >1cm formed of coalescing papules or dermal infiltration
Plaques in a cat with cutaneous lymphoma
pustule
Raised epidermal infiltration of pus
Pustules on the abdomen of a dog with superficial staphylococcal pyoderma.
scale
Accumulation of loose fragments of stratum corneum
Loose, large scales due to ichthyosis in a Golden Retriever
scar
Fibrous tissue replacing damaged cutaneous and/or subcutaneous tissues
Scarring (right) following the healing of an ulcer (left) in a dog with sterile nodular dermatitis
serpiginous
Undulating, serpentine (snake-like) arrangement of lesions
Serpiginous urticarial lesions on a horse
telangiectasia
Permanent enlargement of vessels resulting in a red or violet lesion (rare)
Telangiectasia in a dog with angiomatosis
ulcer
A defect in epidermis that penetrates the basement membrane. Histopathology may be needed to differentiate from an erosion.
Ulcerations of the skin of a dog with vasculitis.
urticaria
Wheals (steep-walled, circumscribed elevation in the skin due to edema ) due to hypersensitivity reaction
Urticaria in a horse
vesicle
Fluid-filled elevation of epidermis, <1cm
Vesicles and bullae on ear pinna due to bullous pemphigoid
wheal
Steep-walled, circumscribed elevation in the skin due to edema
Wheals associated with intradermal allergy testing in a horse
