The hair shaft: normality, abnormality, and genetics

Trichographic features of hair from normal black Dobermann pinscher dogs

BACKGROUND

Dobermann dogs are predisposed to colour dilution alopecia and follicular dysplasia. Limited information is available regarding the trichographic features of normal canine hair shafts, including those from Dobermanns, with no studies of inter-observer agreement for canine trichographic features.

OBJECTIVES

To characterize the trichographic features of normal black Dobermann hair shafts evaluating the following variables; gross appearance, primary versus secondary hairs, colour change, tip structure, curling, twisting, bending, cuticle changes (breaks, compression, loss or abnormal overlapping), fractures and variations in hair diameter.

ANIMALS

Twenty client-owned, normal, black Dobermanns of different ages and genders.

METHODS AND MATERIALS

A systemized trichographic evaluation of hair samples from five body locations, which were evaluated independently by two observers, and inter-observer agreement evaluation. Kappa statistics, positive and negative agreement were determined.

RESULTS

Agreement between investigators ranged from 87% to 99% for each examined variable. Kappa statistics showed excellent (0.81-1.00) to substantial agreement (0.61-0.80) for all variables with the exception of moderate agreement (0.41-0.60) for cuticle compressions and variations in hair diameter. A novel finding of a "round hair tip" was made, which was more commonly found on the dorsal head. Colour change to the proximal hair shaft was more common on the thighs and flanks.

CONCLUSIONS AND CLINICAL IMPORTANCE

Trichographic features of 500 hairs collected from 20 normal black Dobermann dogs are described. A previously unreported finding of round hair tips was seen. We describe a systematic approach for evaluating hair shafts that can be applied in future studies for both normal and abnormal Dobermanns, and potentially other dog breeds.

Trichoscopy in genetic hair shaft abnormalities

BACKGROUND

Diagnosis of hair shaft abnormalities is based on light microscopic examination of more than 50 plucked hairs. The aim of this study was to verify whether hair shaft abnormalities may be visualized by trichoscopy (hair and scalp videodermoscopy) and to analyze trichoscopic features of common genetic hair shaft dysplasias.

METHOD

Patients with known genetic hair shaft disorders were included into the study. Trichoscopy was performed with the use of Fotofinder II videodermoscope. Images performed at 20-fold and 70-fold magnification were analysed. In selected cases 160-fold magnification was used for better visualization of hair shafts.

RESULTS

Our results show that characteristic light microscopy features of Netherton syndrome, monilethrix, woolly hair syndrome, pili torti, pili annulati and trichothiodystrophy may be visualized by trichoscopy.

CONCLUSION

Genetic hair shaft abnormalities may be diagnosed by trichoscopy in a single diagnostic session without the need of plucking or cutting them for diagnostic purposes.