Wood’s Lamp Examination Wood’s Lamp Mercury vapour UV lamp with an incoorporated Wood’s filter (barium silicate glass with 9% metal oxide. Emits UV rays.
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Wood’s Lamp Examination
Wood’s Lamp
Mercury vapour UV lamp with an incoorporated Wood’s filter (barium silicate glass with 9% metal oxide.
Emits UV rays in the wavelength of 360 nm
Wood’s Lamp Examination
Uses a)Diagnosis of taenia capitis Gives rise to greenish fluorescence Microsporum species and trychophyton
schoenleonii are the main fluorescing species
b)Diagnosis of bacterial infections Erythrasema gives a coral pink colouration
c) Examination of extent of pigmentary disorders
Easily accentuates the distinction between slightly hypopigmented and normal skin areas
Enhances the hypopigmented lesions e.g. ash leaf macules in light skin patients
d) Diagnosis of porphyria Pinkish red or orangish red fluoresence in urine
which is intensified on addition of dilute HCl Similar fluoresence in faeces
e) Detection of drug deposits
Demonstrates yellow fluoroscence deposits in teeth and mepacrine in nails
Mycologic Examination
KOH MountSample is put on a glass slide and
an aquous solution of 20% KOH is addedbefore applying the cover slip
Examine the slide under microscope after 20-30 min
Fungal hyphae are easily visible
KOH Mount
Specimens to be takenDisease suspected Specimen
Tinea corporis
Tinea cruris
Tinea unguium
Tinea capitis
Ptyriasis versicolor
Candidiasis
Scales/roof of vesicles
Scales/roof of vesicles
Nail clippings, Subungual debris
Plucked hair, Scales
Scales
Contents of pustule, Vaginal discharge
Diagnosis of Scabies
Presence of mite,ova or faeces in scrapings of paules,vesiculesor burrows confirms the diagnosis
METHOD Drop of mineral oil placed on a sterile
scalpel blade is applied onto a lesion which is then scrapped vigrously till tiny flecks of blood are visible in the oil.The material is transferred onto a glass slide and examined for mites,ova or faeces
Tzanck Test
Cytological examination of skin blisters Test is done in vescicular and bullous lesions
METHOD Early lesion is choosen,deroofed and the
excess fluid is gently blotted with gauze.The floor of the blister is then scrapped gently with a scalpel blade and the material so obtained is spread on a glass slide and stained with Giemsa stain
Tzanck Test
Role of Tzack smear in diagnosis of skin conditions
Microscopic findings Diagnosis
Acantholytic cells
Multinucleated giant cells
Pemphigus
Herpes simplex & Herpes zoster
PATCH TESTS
Detects antigens responsible for type IV allergy (allergic contact dermatitis)
Antigens Used Test the suspected antigen as well as
antigens which are present in the material which is likely to be used as a substitute
If theseare not known a standard battery of antigens can be used
Interpretations of patch testsClinical findings Grading
No reaction
Doubtful reaction
Weak reaction
Strong reaction
Extreme reaction
Irritant reaction
Normal skin
Minimal erythrema
Erythrema
Erythrema and oedema
Erythrema and
vescicular/bullous findings
Cautrisation
0
1+
2+
3+
4+
IR
PHOTOPATCH TESTING
Done to establish cause in photoallergic contact dermatitis
METHOD Antigens are applied,as in routine pach
testing but in duplicate. At 24 hrs , one set of patches are
irradiated with UVA
Interpretation of photopatch testReading at site exposed to UVA
Reading at unexposed site
Interpretation
- ++ + ++
0 0 + +
No allergyPhotoallergyContact allergyContact allergy with photoaggravation
SKIN BIOPSY
Techniques of Taking Biopsy
Two common techniques Punch biopsy Scalpel biopsy
Punch Biopsy Punch biopsies can be done rapidly, with or without suturing of the
wound A punch-biopsy instrument of appropriate size is needed
METHOD A local anesthetic is usually injected at the site. The operator
rotates the instrument until it penetrates to the subcutaneous level. The circle of tissue is then removed. Bleeding can be stopped with pressure or by the use of one or two sutures. An elliptical wound instead of a circular wound can be produced by stretching the skin perpendicular to the desired suture line before the punch is rotated. The resultant scar, after suturing, is neater
Punch biopsies are inadequate for evaluation of vesiculobullous diseases
Scalpel Biopsy
A scalpel is used to slice off a lesion Performed superficially or deeply Hemostasis can be accomplished by
pressure, light electrosurgery, Monsel solution, or aluminum chloride solution
Not recommended for excision of melanocytic lesions
Processing of Skin Biopsy Apart from routine H&E staining special stains can be used for various tissues and to identify different organisims
Stain Colour
OrganismsMycobacteriaFungi
Fite stainPAS
PinkRed
Deposits GlycogenAcid mucopolysaccharides
Amyloid
PASToluidine blueAlcian blue
Congo red
RedBlue
Orange pink with apple green birefringence
Skin componentsCollagenElastic fibresMast cell granules
Masson’s trichomeVerhoef-van giesonVerhoef-van giesonToluidine blue
Green RedBlackPurple
Precautions While Taking a Skin Biopsy
Biopsy a new lesion or active edge of a proressing lesion
Avoid legs (slow healing), upper trunk(because of tendency of keloid formation),exposed parts(cosmetic objections) & bony prominces
Do not crush the tissuePlace the proper fixativeLabel samples correctly
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