What is anagen effluvium?
Anagen effluvium refers to hair shedding that arises during the anagen or growth stage of the hair cycle.
This is in contrast to telogen effluvium or hair shedding that arises during the telogen or resting stage of the hair cycle.
Anagen effluvium is due to an acute injury to the hair follicles by an endogenous or exogenous cause, resulting in sudden diffuse shedding of structurally damaged hairs. Diffuse alopecia (hair loss) may occur over a period of days. The alopecia is non-scarring.
Who gets anagen effluvium?
Anagen effluvium is most common in patients of any age, sex, or race receiving chemotherapy.
Individuals with autoimmune conditions such as alopecia areata and pemphigus vulgaris can be affected.
What causes anagen effluvium?
Any insult that impairs mitosis of hair follicle keratinocytes can cause anagen effluvium. Disruption to cell division in the hair matrix makes the hair narrowed at its base and susceptible to breakage just above the zone of keratinisation. The necrotic matrix forms plugs consisting of melanin, keratin and inner root sheath which are extruded through the follicular opening. This process is known as trichomalacia.
An infection may interrupt hair growth in a localised area resulting in a single bald patch or several bald patches. Loose hairs can readily be extracted from the infected area, which may be swollen, boggy and crusted. Examples include:
Anagen effluvium: fungal infection (kerion)
Toxins that can interrupt hair growth include:
- Chemotherapy agents, usually prescribed to treat cancer, especially when multiple drugs are used or they are in high dose. Severe hair loss is reported from doxorubicin, the nitrosoureas, and cyclophosphamide. Other causes are bleomycin, dactinomycin, daunorubicin, systemic fluorouracil, and high-dose methotrexate.
- Other medicines such as colchicine and ciclosporin (ciclosporin more often causes increased hair growth)
- Poisons such as thallium, arsenic, gold and bismuth.
Alopecia develops within 2 to 4 weeks of chemotherapy. It affects most parts of the scalp, but other sites may be affected, such as eyebrows, armpits and genital area.
Anagen effluvium: loss of eyebrows and eyelashes
Radiation to the scalp can result in anagen effluvium. Regrowth of hair may be incomplete or may not occur.
Anagen effluvium due to cranial irradiation for melanoma
Anagen effluvium: autoimmune disease
What are the clinical features of anagen effluvium?
Anagen effluvium presents with abrupt shedding of much of or all of the hair on the scalp, and often from the entire body including eyebrows, eyelashes and body hair. It may leave the scalp partially or completely bald shortly after the traumatic event with up to 90% hair loss over a period of weeks.
Other features depend on the cause of the hair shedding.
Anagen effluvium due to chemotherapy
How is anagen effluvium diagnosed?
The diagnosis of anagen effluvium is usually made by taking a careful history, particularly of recent medicines, and by examining the scalp and shed hair clinically and by dermoscopy/trichoscopy.
In anagen effluvium, the end of the hair that comes from the scalp is tapered, narrowed, irregular, or broken off. Anagen hairs have long roots covered with the inner and outer root sheaths and are pigmented. In contrast, telogen hair is a roundish bulb or club. The follicular openings remain in both conditions.
Anagen effluvium: hair pull
A trichogram (forcible hair plucking within a unit area to determine the ratio of anagen to telogen hair) will show a large proportion of dystrophic anagen hairs.
Scalp biopsy should reveal a normal anagen-to-telogen ratio of any persisting hairs in anagen effluvium due to chemotherapy.
What is the treatment for anagen effluvium?
Anagen effluvium due to chemotherapy is expected to recover fully within 3–6 months of stopping it. The hair nearly always grows back normally, but sometimes patients with straight hair develop curly hair when it regrows. Hair colour may also change.
Suggested treatments for anagen effluvium include:
Anagen effluvium: regrowth
What is the outcome for anagen effluvium?
Anagen effluvium is reversible. The hair follicle resumes normal activity after any toxic agent is withdrawn. Complete regrowth occurs after 3–6 months after chemotherapy in most cases. Sometimes the hair regrows despite the continuation of chemotherapy.
Anagen effluvium due to alopecia areata may persist; recovery is unpredictable.