C2 Hair Shaft Anomalies
CONGENITAL HAIR SHAFT ANOMALIES
Itin PH
Departments of Dermatology, Kantonsspital Aarau and University of Basel, Switzerland

This course focuses on the morphologic aspects of genetic hair shaft disorders. The attendees will learn about the typical hair shaft alterations, which can be recognized under light microscope. Hair dysplasias are congenital or acquired alterations which often involve the hair shaft. Hair shaft abnormalities are characterized by changes in color, density, length and structure. Hair shaft alterations often result from structural changes within the hair fibers and cuticles which may lead to brittle and uncombable hair. The hair of patients with hair shaft diseases feels dry and looks lusterless. Hair shaft diseases may occur as localized or generalized disorders. Genetic predisposition maintains hair shaft abnormalities that are often exacerbated by environmental influences. Hair shaft diseases are separated into those with and those without increased hair fragility. In general optic microscopy and polarized light microscopy of hair shafts provide important clues to the diagnosis of isolated hair shaft abnormalities or complex syndromes. To establish an exact diagnosis of dysplastic hair shafts, a structured history and physical examination of the whole patient are needed which emphasizes other skin appendages such as nails, sweat and sebaceous glands. Profound knowledge on hair biology and embryology is necessary to understand the different symptom complexes. Therapy of hair shaft disorders should focus to the cause. In addition, minimizing traumatic influences to hair shafts, such as drying hair with an electric dryer or permanent waves and dyes, is important. A short hairstyle is more suitable for patients with hair shaft disorders.

AQUIRED HAIR SHAFT ANOMALIES
Ferrando J
Department of Dermatology, Hospital Clinic, University of Barcelona, Spain

Acquired hair shaft disorders are easily recognized under light microscope, but dermoscopy can help in the office diagnosis of hair shaft anomalies. In this presentation we will focus on acquired hair kinking and acquired knots & nodes of the hair shaft. Acquired hair kinking is characterized by the presence of curly hairs with irregular twisting of the hair shaft, of late onset. Usually there are localized flat hairs that follow a diffuse pattern depending on different conditions. We can distinguish: circle (rolled) hairs, acquired pili torti (including corkscrew hair) (APP), and acquired woolly hairs (pseudowoolly hair) (AWH). Circle hairs appear as black dots on the trunk corresponding to a spiral pattern of ingrown body hair. APP is an irregular twisting of the hair and is usually found in areas of scarring alopecia in cases of lupus erythematosus or lichen planopilaris. APT have also been found in ectodermal dysplasias and metabolic diseases. AWH recognized localized forms (“whisker hair”) and diffuse forms: acquired progressive kinking of hair, diffuse partial woolly hair (including acquired partial curly hair) and drug induced curling of hair. Knots & nodes of hair shaft include, mainly, trichonodosis (hair knotting) and distal trichorrhexis nodosa. If we observe knots under the microscope, the diagnosis is easy: trichonodosis, commonly associated also with compulsive hair manipulation. Nodes are common on microscopical observation and may signify different diseases, depending of the type and distribution of the nodes. Flat irregular nodes are very suggestive of artefactual pseudomonilethrix or bubble hair while regular nodes are typical of trichorrhexis nodosa commonly associated to trichoptilosis (split ends). Other interesting conditions that produce specific acquired anomalies to hair shaft is the damage produced by hair cosmetics or styling, including bird’s nest hair, as well as other external causes of acquired hair damage as green hair. In addition, minimizing traumatic influences to hair shafts, such as drying hair, or environmental effects should be avoided.