Hair Shaft Defects
Hair and scalp disease like hair shaft defects needs special microscopic features to diagnose the imperfection and to be able to make recommendations for treatment. A hair shaft defect is a medical condition that causes a physical change in the strength or structure of individual strands of hair. Our hair fibre is made up of numerous different layers including the cuticle, inner root sheath, outer root sheath and the cortex. Hair shaft defect takes place when a faulty hair is formed due to change in the development of the hair strands. Trichorrhexis Nodosa is the most common defect of the hair shaft, a beaded swelling linked with cuticle loss. It can be caused by chemical and mechanical trauma that can be aggravated by the inborn weakness of the hair shaft.
Another hair shaft defect is the Trichoclasis or the common “green stick” wherein the hair shafts consist of a transverse fracture supported by an intact cuticle. In this condition, there is no regular abnormality of the cortex or cuticle. It is caused by trauma and excessive hair care. When it is caused by physical trauma, the affected area shows patchy and irregular damage and gentle hair care can resolve the problem.
A longitudinal splitting of the distal end of the hair is known as Trichoptilosis. Due to cuticular loss from weathering, cortical fibers usually separate like the ragged ends of a rope that result to “frizzies” or “split ends”. It is a common hair fracture due to trauma. In the tapered hairs or the “Pohl-Pinkus Constriction”, portions of hair shaft shows unusual tapering without fracture that may be due to disruption of the anagen phase that is usually seen with chemotherapy drugs causing anagen effluvium or in a condition of hypoproteinemia.