Trichography (hair plucking)

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• Hair examination is a valuable aid to differential diagnosis of skin and hair disorders.
• Useful technique - analysis for fungal diseases, parasitic diseases, congenital/hereditary diseases.

• Self-inflicted (versus non-self-inflicted) hair loss.
• Trichorrhexis nodosa.
• Shaft disorder of Abyssinian cats .
• Pili torti.
  

Of diagnostic assistance in

• Some nutritional and congenital hair dysplasias.
• Dermatophytosis .
• Anagen defluxion .
• Telogen defluxion .
• Endocrine alopecia .
• Some pigmentary disturbances.
• Some ectoparasite infestations: cheyletiellosis , lice , demodicosis .
• Chediak-Higashi syndrome of long-haired cats.

• Easy technique.
• Inexpensive.
• Accurate.
• Alternatives may be expensive, eg biopsy, fungal culture.

• Time consuming.

• Some expertise required for interpretation.

• Skin scraping .
• Fungal culture.
• Skin biopsy .

• 5-10 min.
• Experience required for choice of samples to be taken.

• 15-60 min.
• Examination for some diseases will take less time.

• History and clinical examination will indicate which diseases are likely.

• Trichorrhexis nodosa.
• Anagen defluxion .
• Telogen defluxion .
• Shaft disorder of Abyssinian cats.
• Pili torti .
• Some nutritional and congenital hair dysplasias.
• Dermatophytosis
• Endocrine alopecia.
• Some pigmentary disturbances.
• Keratinization defects.
• Chediak-Higashi syndrome long-hair cats .

• Self-inflicted versus non-self-inflicted hair loss.
• Ectoparasite infestations: Cheyletiella spp eggs and lice, or demodicosis .

• Pair of good hemostats.
• Microscope with x4, x10 and x40 objectives.

• Good quality microscope.
• Epilation forceps (rubber tipped).

• Microscope slides.
• Coverslips.
• Liquid paraffin or mineral oil for mounting.

• Sample fully developed and early lesions.
• For dermatophytosis sample the expanding edge of the lesion.

• Manual restraint usually adequate.

• Grasp 50+ hairs with hemostats; pluck hairs gently but firmly in direction of their growth.

• Either Place on microscope slide under a cover slip with liquid paraffin.
  Or For suspected dermatophytes place on microscope slide with 10% potassium hydroxide and leave in warm place for 15-20 minutes.
   Positive results for dermatophytosis most often obtained when Wood's lamp-positive hairs are sampled.
• Examine using x4, x10 and if necessary x40 objectives.

• Assess development stage of hair:
  • Telogen root is club shaped and smooth.
  • Anagen root is distorted and appears traumatized.
• Assess for scaling around root.
• Scale may represent folliculitis; follicular hyperkeratosis (keratinization defects, especially in long-hair cats).
• Examination of pigmentation: in Chediak-Higashi syndrome (Blue smoke long-hair cats), macromelanosomes may accumulate around the root - large pigmented structures.
• Examination for Demodex mites .

• Normal shaft is uniform in diameter and tapers slowly to the tip, with sharply demarcated cortex and medulla; pigmentation should not vary greatly from one hair to next in regions where coat color is sam .
• Examine abnormal hairs under higher magnification.

Interpretation of microscopic findings


• All hairs in telogen: telogen defluxion , follicular arrest.
• Inappropriate numbers in telogen: (eg mostly telogen during summer when ratio should be 50:50), nutritional, endocrine or metabolic disease .
• Shaft curled, misshapen and malformed: underlying nutritional or metabolic disease or pili torti.
• Cleanly broken shaft: trauma.
• Breakage of hairs with abnormal shafts: congenitohereditary disorders and dermatophytosis.
• Unusual pigmentation: external contamination, nutritional imbalances, endocrine disorders, idiopathic pigmentary disorders, Chediak-Higashi syndrome long-haired cats.
• Parasites: Demodex spp, lice eggs or adults, Cheyletiella eggs, fungal spores.

• Examination of tip for signs of damage - may be the only sign of self-trauma.

• Too few hairs examined.
• Hairs taken from the wrong site.
• Microscope inadequate for adequate examination.

• Moriello K A & Mason I S (1995) Handbook of Small Animal Dermatology. 1st edition. Oxford: Pergamon Press. pp 23-25. (Hair examination for fungal elements.)
• Scott D W, Miller W H & Griffin C E (1995) Muller and Kirk's Small Animal Dermatology. 5th edition. Philadelphia: W B Saunders. p 98. ISBN 0 7216 4850 9 (Detailed account with photographs of normal and abnormal hairs.)

• David Scarff BVetMed CertSAD MRCVS, Anglian Referrals, 2 Highlands, Old Costessey, Norwich, Norfolk NR8 5EA, UK. Tel:/Fax: +44 (0)1603 743415.
• Dr Karen Campbell DVM MS DipACVIM DipACVD, University of Illinois, Veterinary Medical Teaching Hospital, 1008 West Hazelwood Drive, Urbana, IL 61802, USA.

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