Trichonodosis (Trichorrhexis nodosa) - one of the most common hair shaft defects - a focal defect in the hair fiber. When observed under the microscope most of a hair shaft looks entirely normal. However, in isolated spots along the length of a fiber swelling and/or fraying can be seen. These focal defects develop where there is an absence of cuticle. The cuticle encases the hair cortex in a strong almost impenetrable layer. It provides physical support and helps protect the cortex of a hair shaft from environmental factors such as ultra violet light, chemicals such as detergents and physical action such as hair brushing. If the cuticle is absent then the cortex underneath is directly exposed. The cortex is less resistant to the physical and chemical factors in the environment compared to the cuticle. Where the cortex is exposed its integrity is broken down. The chemical bonds that maintain the hair structure can break down and the hair becomes more flexible and weaker. The hair may split and fray into minute strands at the point of cuticle break down. This focal disruption of the hair fiber is a prime area for hair shaft breakage. As we comb, brush, and generally manipulate our hair, these defective nodes in the hair fiber may break. Causes of trichorrhexis nodosa can be congenital or acquired. Some people have naturally weak hair where the cuticle is not properly produced. This influence is often hereditary and runs in families. Congenital trichorrhexis nodosa is very rare and it often first develops at a very young age. Abnormal production of hair fiber that is irregular and brittle can occur in metabolic disorders such as those that involve abnormal urea synthesis, abnormal copper or zinc metabolism, or defective cysteine or sulfur incorporation into hair fiber (trichothiodystrophy). Trichorrhexis nodosa is more likely to be acquired through excessive manipulation of hair. Too much brushing, hairstyles that put constant stress on the hair, excessive washing, dying, and perming may disrupt the cuticle in focal areas along a hair shaft. Trichorrhexis nodosa is seen in people who repeatedly use hot combs or permanent waves to style their hair. Once the cuticle is removed then the hair cortex swiftly breaks down. Trichorrhexis nodosa develops in association with a range of other hair diseases. Any hair condition that weakens the hair shaft and/or results in abnormal cuticle formation can result in Trichorrhexis nodosa like hair breakage. Hair loss through breakage can be seen in conditions such as alopecia areata as a secondary phenomenon. Treatment depends on the considered cause of the focal defects. If the hair production is believed to be abnormal then treatment will focus on the hair follicle and improving the strength of hair fiber. Where the defect is the result of excessive grooming the obvious action is to reduce the amount of hair manipulation. People are encouraged to stop using brushes, avoid hair styling that involves chemicals and use only very mild shampoos. Once the integrity of the hair fiber is broken down there is little that can be done to repair it. Often the only answer is to choose a short hair style and cut off the defective hair. It may take some time for hair to recover from trichorrhexis nodosa. New, healthy hair has to grow to replace the defective fibers. It may take several months or even years before scalp hair completely recovers.  

Trichoptilosis (from Greek root "tricho" meaning hair and "ptilosis" meaning "falling out of the eyelashes") - is the "splitting of hairs at the ends, often referred to as "split ends" - a longitudinal dissection of hair. The primary cause is physical stress to the hair from heat or mechanical means. Split ends are more likely to form on a hair that has been snapped or broken from yanking a comb through tangled hairs than on one that has been cut cleanly and combed gently. Excessive use of chemicals, such as perms and dyeing, may also strip protective layers off the outside of the hair shaft and thereby weaken the hair. Quite often this may be due to low sebaceous glands secretion, also this may be a symptom of Alopecia Areata or a fungal and other diseases, like tuberculosis, syphilis, anemia, etc. Trichoptilosis can often be visible among the long, dry hair, when the hair along its length or just the tip has a clearly seen longitudinal dissection of any length at any part of the hair, sometimes two or more cleavages on the same hair shaft, etc. In addition, trihoptilosis may sometimes develop not only in the hair shaft, but also in the hair bulb, this leads later on to an atrophy of the hair bulb. There is no way to repair split ends; when they occur, the split part of the hair must be trimmed. They can, however, be repaired purely aesthetically by physically separating the different strands of hair from each other below the split-point. This is time-consuming and inefficient though, as you have to manually check for split-ends. but by doing so, the "half hairs" will appear grey, so it is not recommended for those with dark hair. Split ends prevention is based on reducing or eliminating the causes. Trimming the ends of the hair at least several times a year may prevent split ends by cutting off the hair that is at highest risk for splitting.

Trichoclasis is hair breakage that is seen as a clean fracture across the hair fiber. These fractures are normally longitudinal, however sometimes diagonal fratures are observed - an ideopathic trichoclasis conddition. The disease appears at any age, most often affects women. The disease manifestation is hair suddenly start to break at the slightest tension or break off at one even level in certain sections of the hairy part of the head. This level of hair length may vary in different individuals from several mm up to 5 - 10 cm. Sometimes these breakage sections increase, sometimes get smaller, sometimes at a distance from each other and sometimes merge with each other. The hair in these areas are growing well, but some day there is a disease outburst, often repetitive. Hair shaft structure is usually normal, but the hair is thinner. The scalp skin at the hair breakage sites may be normal or have some inflammation, dryness, peeling, itching, etc. Trichoclasis may develop secondary to hair conditions that make hair fiber weak. It can also be seen in normal hair where vigorous grooming stresses the fiber to such an extent that the hair suddenly snaps and breaks off. It is common to see some trichoclasis as a result of trichotillomania (obsessive hair plucking). Treatment for trichoclasis involves reducing the physical manipulation of hair and the recommendation of less vigor in brushing or combing. 

Trichothiodystrophy is a congenital disorder that involves production of abnormal, brittle hair. The hair complications are usually only part of the disease. Frequently, trichothiodystrophy also involves problems with hair related structures such as the teeth, eyes (cataracts) and nails (onchodystrophy). It can also involve stunted growth, mental retardation, skin sensitivity to light and skin ichthyosis. There are several different forms of trichothiodystrophy and occasionally some individuals are reported as having the brittle hair symptom but without any other symptoms. Brittle hair is one of the diagnostic markers for trichothiodystrophy. The individual has what looks like sparse short hair growth over the scalp and elsewhere on the body. Under the microscope the hair can be seen to have a squashed oval shape in cross section, an irregular diameter along its length, has abnormal or no cuticle, and with abnormal irregular pigment incorporation along its length. Where trichothiodystrophy is suspected, hair samples are often tested for sulfur content and cysteine aminoacid content. Trichothiodystrophy affected hair has only around 50% of the sulfur and cysteine content found in normal hair. The hair follicles of trichothiodystrophy affected individuals are all fully functioning but the hair is so brittle that once it emerges from the skin and becomes exposed to the environment trichorrhexis nodosa, trichoclasis, and trichoschisis occur in the hair fibers. The breakage and fracturing in the brittle hair result in the short, sparse appearance. Treatment is very difficult as trichothiodystrophy is a genetic disease. There is no form of gene therapy available now or in the foreseeable future for trichothiodystrophy. Treatment usually involves preventative measures, avoiding excessive hair styling and exposure to light. Some dermatologists also attempt to use cysteine aminoacid supplementation in the diet.

Trichomycosis or Piedra, meaning stone in Spanish, is an asymptomatic fungal infection of the hair shaft, resulting in the formation of nodules of different hardness on the infected hair. The two types of piedra arise in different climatic regions. Black piedra occurs frequently in humid, wet tropical areas, while white occurs in semitropical and lower temperate countries. Both clinical varieties of piedra are mostly asymptomatic. However, according to the severity of the infection, progressive weakness of the hair shaft occurs causing the hair to be brittle. Black piedra is a condition that is characterized by the presence of firmly adherent black, hard, gritty nodules, which are composed of a mass of fungus cells on the hair shaft, and cause disintegration and breaking of the hair. These stone-hard black nodules are usually localized to the scalp, but may also be seen on hairs of the beard, moustache and pubic hair, with the fungal activity limited to the cuticle. Black piedra is more frequent and less sporadic than white piedra, and the tiny nodules can be recognized by a metallic sound when brushing hair. Most commonly, the scalp hair is affected and nodules are present on the frontal, occipital and parietal scalp. White piedra is characterized by white-to-tan nodules along the shafts of hair in the scalp, beard, eyebrows, eyelashes and groin, genital and perigenital areas. Numerous discrete soft nodules that are lightly pigmented are attached to the hair shaft and produce a gritty sensation when palpated. The nodules may be detached easily and the affected hairs may be split or broken. Clinically many hair disorders can be confused with piedra. Therefore, differential diagnosis, the process involved in distinguishing between two or more diseases and conditions with similar symptoms by systematic analysis of the clinical and diagnostic data, is essential, before arriving at a conclusive diagnosis and commencing therapy. White and black piedra should be distinguished from each other. It can be noted that black piedra as compared to white piedra, presents a harder nodule that adheres to the hair shaft. Piedra can often be confused with pediculosis or lice infestation. Infections can co-exist with dermatophyte or candida infections, and erythrasma, a bacterial skin infection characterized by reddish brown, slightly raised patches, especially in the armpits and groin. White piedra should be differentiated from tinea capitis (a skin and hair follicle infection), and trichomycosis axillaris (an infection of the axillary and pubic hairs with the development of yellow, black, or red concretions around the hair shafts).