The different types of alopecia associated with loss of hair on the scalp include,
1. Androgenetic alopecia (Genetic hair loss)
Androgenetic alopecia, also known as male pattern hair loss is a major problem affecting men and is such that by the age of 50, up to 50% of men who are genetically predisposed will be affected. It is characterised by progressive, patterned hair loss from the scalp and its prerequisites are a genetic predisposition and sufficient circulating androgens (steroid hormone such as testosterone or androsterone, which promotes male characteristics). According to Sinclair (1998) every Caucasian male possesses the autosomal inherited predisposition, and as such, 96% lose hair to some degree. Sinclair also mentions that Caucasian men are four times more likely to develop premature balding than Black men. Hair loss does not usually start until after puberty with an extremely variable rate of progression [1, 5].
The condition is also fairly common in women and is referred to as female pattern hair loss. In women, "it is characterised by a diffuse reduction in hair density over the crown and frontal scalp with retention of the frontal hairline" . Birch et al (2002) make mention of the fact that in some women, the hair loss may affect a small area of the frontal scalp whilst in others the entire scalp is involved. In advanced female pattern hair loss, the hair becomes very sparse over the top of the scalp bit a rim of hair is retained along the frontal margin. The vertex (crown or top of the head) balding seen in men is rare in women; however, a female pattern of balding is not uncommon in men . The androgen-dependent nature or the genetic basis of female pattern hair loss has not been clearly established, although a study carried out by Sinclair et al (2005) showed that androgens play an important role in the development of female pattern hair loss.
2. Alopecia areata (AA)
Alopecia areata (AA) is a common, immune-mediated, nonscarring form of hair loss, which occurs in all ethnic groups, ages (more common in children and young adults), and both sexes, and affects approximately 1.7% of the population [8, 9]. Alopecia areata is unpredictable and patients usually present with several episodes of hair loss and regrowth during their lifetime. Recovery from hair loss may be complete, partial, or nonexistent. It is thought that 34 to 50% of patients with AA will recover within a year whilst 15 to 25% will progress to total loss of scalp hair or loss of the entire scalp and body hair where full recovery is unusual [8, 11]. It usually presents as a single oval patch or multiple confluent patches of asymptomatic (without obvious signs or symptoms of disease), well circumscribed alopecia with severity ranging from a small bare patch to loss of hair on the entire scalp. Frequent features of AA patches are exclamation mark hairs, which may be present at its margin; the exclamation mark hairs are broken, short hairs, which taper proximally. The hair loss from AA may be the only obvious clinical abnormality or there may be associated nail abnormalities. Other less common associated diseases include thyroid disease and vitiligo [4, 10, 11].
Clinical presentation of AA is subcategorised based on the pattern and extent of the hair loss. If categorised according to pattern, the following are seen;
a. patchy AA, which consists of round or oval patches of hair loss and is the most common,
b. reticular AA, which is a reticulated (networked) pattern of patchy hair loss,
c. ophiasis band-like AA, which is hair loss in parieto-temporo-occipital scalp (middle-side-back of scalp),
d. ophiasis inversus, which is a rare band-like pattern of hair loss in fronto-parieto-temporal scalp (front-middle-side of scalp), and
e. diffuse AA, which is a diffuse decrease in hair density.
[Taken from Shapiro J and Madani S, 1999]
If categorised according to the extent of involvement, the following are seen;
a. alopecia areata, which is the partial loss of scalp hair,
b. alopecia totalis, which is 100% loss of scalp hair, and
c. alopecia universalis, which is 100% loss of body hair.
[Taken from Shapiro J and Madani S, 1999]
3. Telogen Effluvium (TE)
Telogen effluvium is an abnormality of hair cycling, which results in excessive loss of telogen (resting phase of hair cycles) hairs and is most common in women. Women with this disorder would usually notice an increased amount of loose hairs on their hairbrush or shower floor. Daily loss of hair may range from 100 to 300 hairs. It is thought that TE may unmask previously unrecognised androgenetic alopecia. The most common underlying cause of TE is stress; other causes include certain diseases such as thyroid and pituitary diseases, some medication and child birth, to mention a few. In many cases however, no cause can be found. TE usually begins two to four months after the causative event and can last for several months [4, 12]. Unlike some other hair loss conditions, TE is temporary and hair regrowth is possible . Telogen effluvium presents in about three forms;
a. Acute telogen effluvium, where shedding of hair is expected to cease within 3 to 6 month
b. Chronic diffuse telogen hair loss, which is telogen hair shedding persisting longer than 6 months. Common causes include thyroid disorders, acrodermatitis, profound iron deficiency anaemia, and malnutrition.
c. Chronic telogen effluvium (CTE) is the most common cause of hair loss in women, affecting 30% of females, between the ages of 30 and 60 years old, in the UK. CTE is such that there is a relative change in the proportion of growing to resting hair and in most cases, excessive shedding of hair has been present for at least 6 months. According to Rushton et al (2002) studies have shown that 95% of CTE cases arise from a nutritional imbalance involving the essential amino acid L-lysine and iron. Other common causes of CTE include drugs, thyroid disease and childbirth [1, 11].
4. Cicatricial alopecia (scarring alopecia)
Circatricial alopecia, also known as scarring alopecia, refers to a group of rare hair disorders resulting from a condition that damages the scalp and hair follicle. They present as areas of hair loss in which the underlying scalp is scarred, sclerosed, or atrophic. In other words, the disorders destroy the hair follicle and replace the follicles with a scar tissue consequently causing permanent hair loss. Conditions associated with circatricial alopecia include autoimmune diseases such as discoid lupus erythematosus, scalp trauma, infections such as tuberculosis and syphilis, and radiation therapy. Circatricial alopecia affects both adults and children, and may present as primary or secondary circatricial alopecia [4, 13].
5. Chemotherapy-related alopecia
Alopecia caused by chemotherapy may vary from slight thinning of the hair to complete baldness. The extent of alopecia depends on the choice of drugs and its dose. Drugs which cause severe alopecia include methotrexate, vinblastine, adriamycin, ifosphamide, vincristine, and taxoids to mention a few. When drugs are used in combination, which is usually the case with many treatment regimes, the incidence and severity of alopecia can be greater than usual. According to Randall et al (2005) "chemotherapy-related alopecia has been rated by patients as one of the most severe, troublesome and traumatic chemotherapy-related side effects". Hair loss due to chemotherapy is not permanent and as such, the hair will grow back once treatment has ended .
6. Traumatic alopecia
This is usually a very common cause of hair loss in women of some ethnic backgrounds (particularly women of African/Caribbean descent). It is caused as a result of hair grooming techniques by the use of hair reshaping products such as relaxers, straighteners, hot combs, foam rollers and permanent wave products, as well as hair braiding methods. These techniques damage hair follicles over time . Traumatic alopecia is divided into three categories;
a. Traction alopecia, which results from persistent pulling of the hair by tight rollers, tight braiding or ponytails. The use of blow-dryers, vigorous combing or brushing and bleaching of the hair can also contribute to hair breakage. Thinning begins above the ears and the forehand, and if the causative styling methods are not stopped, irreversible hair loss can result as the hair follicles are destroyed [15, 16].
b. Chemical alopecia, which results from the use of commercial relaxer and styling products. These products contain chemicals such as thioglycolates, which create curls or straighten the hair by destroying the disulphide bonds of keratin. Apart from curling or straightening the hair, these chemicals may have irritant effects on the scalp, which can result in hair shaft damage, inflammation of the scalp and loss of hair roots. All these can lead to irreversible damage of the hair follicles [15, 16].
c. Hot-comb alopecia, also known as follicular degeneration syndrome, results from the excessive use of pomades with a hot comb or iron, which leads to a gradual destruction of hair follicles. When pomade comes in contact with a hot comb or hot iron, it liquefies and drips down the hair shaft into the follicle. This results in chronic inflammatory folliculitis, which can lead to scarring alopecia and consequently permanent hair loss. Thinning usually begins at the crown and then spread evenly throughout the head. The condition is irreversible [15, 16].