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