Hair loss can severely affect patients. Dr Anton Alexandroff describes the most common types of alopecia.
"Hair loss is extremely common. Half of the population have alopecia by the age of 50 years. Men and women are affected in equal proportion. Alopecia can have a significant impact on patients’ quality of life and psychological well being."
"For instance, it has been shown that women having treatment for breast cancer are affected more by hair loss than by mastectomy. In my practice, a consultation for hair loss usually takes more time than a consultation for any other condition, including skin cancers."
There are several types of alopecia, which can be classified by underlying pathological mechanisms and the possibility of regrowth. The former can guide possible therapeutic options.
The most common types of alopecia are non-scarring alopecia (pattern hair loss, previously commonly referred to as androgenetic alopecia), telogen effluvium and alopecia areata. These three types represent over 75% of cases of alopecia. Scarring alopecia is also important to note because this hair loss is irreversible, so prompt diagnosis and treatment is crucial.
Pattern hair loss
In non-scarring alopecia, hair follicles are not destroyed and there is always a possibility of hair regrowth. There are usually no signs of overt inflammation such as erythema, scale or scarring.
Male pattern hair loss is characterised by non-scarring retraction of the hairline and hair loss on the crown. Positive family history is common. It is advisable to do a thyroid function test and check ferritin levels. If ferritin is below 70mcg per litre, iron supplements are recommended and may produce regrowth in a some patients. Further treatment options include topical minoxidil and oral finasteride. Baseline prostate specific antigen levels should be documented before starting finasteride. Hair transplantation is an expensive but effective option (figure 1).
Female pattern hair loss is characterised by thinning of hair on the crown with relative preservation of hair density on the posterior aspect of the scalp. It is advisable to do a thyroid function test and check ferritin and testosterone levels. Treatment includes topical minoxidil and, if desirable hair transplantation.
Telogen effluvium is characterised by excessive hair shedding. This is caused by a relatively large number of hair follicles simultaneously entering the resting, or telogen, phase of the hair cycle. Clinically, telogen effluvium presents with a history of hair shedding and diffuse thinning of hair on the whole scalp. On a gentle hair pull test two or more hairs are shed (providing the patient has not washed their hair within 24 hours).
Common causes of telogen effluvium are illnesses, pregnancy, crash diets, medications and stress. Any medications can cause telogen effluvium, but common culprits include anticoagulants, antihypertensives, hormones, anticonvulsants, antidepressants, retinoids, cimetidine, cholesterol lowering drugs, and NSAIDS (table 1).1 Abnormal thyroid function and ferritin levels below 70mcg per litre may also be relevant. In a significant proportion of patients no cause is identified.
Telogen effluvium starts around three months after an inciting event (this can range from 1-6 months). Anxiety related to hair loss can cause or maintain telogen effluvium. It is important to reassure patients that they will not go bald because of telogen effluvium. If the trigger is identified and removed hair shedding should resolve and hair density should recover, although this can take six months or longer.
Alopecia areata is common; it has around a 2% lifetime risk. It can affect any part of the body including eyebrows and eyelashes. Alopecia areata is characterised by well-defined patches of complete non-scarring hair loss. There are no accompanying symptoms or signs of inflammation such as scale, erythema or pruritus. Hair follicles are visible. There may be exclamation sign hairs, which are wider at the top and taper towards the scalp. The scalp will show tenting on gentle hair pull. Alopecia areata is associated with other autoimmune diseases including atopic dermatitis, vitiligo and thyroid disease.
Alopecia totalis is defined as complete hair loss on the head and alopecia universalis is complete hair loss on the scalp and body.
There is a potential for regrowth; spontaneous hair growth is common when the disease is limited and often happens within the first year. Expectant treatment is a reasonable option. Potent topical corticosteroids are recommended for the treatment of alopecia areata on the scalp in adults. Intralesional corticosteroids are the second-line treatment for limited scalp disease. A course of oral steroids can be considered as a one-off option. Unfortunately minoxidil, tacrolimus ointment and pimecrolimus cream were not effective in clinical trials. Although topical bimatoprost is an effective treatment to make eyelashes longer and thicker, it does not work for alopecia areata. Newer therapeutic agents including JAK inhibitors showed promising results in phase 2 clinical trials.
Topical diphencyprone immunotherapy is an effective treatment which has been used off licence in NHS and privately for over 20 years.2 In patients who failed corticosteroid therapy it induces 50-75% regrowth. Half of the patients maintain regrowth and another half require a maintenance treatment.
Scarring alopecia causes hair follicle destruction and hair loss is irreversible, so it is important to diagnose and treat scarring alopecia promptly. Scarring looks like shiny scalp skin without visible hair follicles when the scalp is examined with good light and under magnification. The aim of treatment is to limit further hair loss rather than facilitate hair regrowth.
Scarring alopecia can be caused by fungal or mycobacterial infection or significant endogenous inflammation.
Tinea is usually characterised by red, scaly patches with hair loss or by appearance of scaly black dots, and rarely it can cause scarring alopecia. Tinea can often be identified elsewhere on the skin or in siblings and pets. Inflammatory tinea may cause kerion. Fungal infection of the scalp usually requires systemic treatment which can be combined with topical treatments.
Scarring alopecia not caused by infection can be classified based on inflammatory infiltrate. Lymphocytic scarring alopecia includes discoid lupus and lichen planopilaris (LPP).
Discoid lupus is characterised by patches of scarring with follicular plugging. Treatments include super potent topical corticosteroids, tacrolimus, systemic hydroxychloroquine, retinoids and immunosuppressive treatments such as azathioprine, methotrexate and mycophenolate.
Lichen planopilaris is a relatively common lymphocytic alopecia. It is characterised by perifollicular erythema and scale and often causes irreversible hair loss. Variants include frontal fibrosing alopecia, pseudopelade (which has the appearance of footprints in the snow) and central centrifugal alopecia.
Neutrophilic alopecia includes folliculitis decalvans and dissecting cellulitis of the scalp. This is generally managed with antibacterial treatments, but retinoids and immunosuppressants may also be considered. Topical and systemic antimicrobials are often employed. A combination of oral rifampicin and clindamycin is worth trying. Dapsone can also be tried.