Anagen Effluvium

Understanding Anagen Effluvium

Anagen effluvium is a rapid and widespread form of hair loss characterized by the abrupt shedding of hairs that are still in the anagen, or active growth, phase of the hair cycle. This differs significantly from other forms of hair loss, such as telogen effluvium, where hairs shed after prematurely entering the resting (telogen) phase.

The Hair Growth Cycle

To understand anagen effluvium, it's essential to first grasp the basic hair growth cycle:

• Anagen Phase: The active growth phase, lasting 2–7 years. Approximately 80–90% of hairs are in this phase at any given time.
• Catagen Phase: A transitional phase, lasting 2–3 weeks, during which hair growth stops and the hair follicle shrinks.
• Telogen Phase: The resting phase, lasting 2–4 months. Approximately 10–15% of hairs are in this phase. At the end of the telogen phase, the old hair sheds, and a new anagen hair begins to grow.

In anagen effluvium, the hair follicle's ability to produce hair is suddenly disrupted during the anagen phase, leading to the breakage and shedding of actively growing hairs. This results in a very rapid and often extensive loss of hair.

Causes of Anagen Effluvium

The most common and well-known cause of anagen effluvium is chemotherapy. Chemotherapeutic drugs are designed to target rapidly dividing cells, including cancer cells. Unfortunately, hair follicle cells, which also divide rapidly, are often affected.

Other causes can include:

• Radiation therapy: Especially when delivered to the head and neck.
• Poisoning by certain toxins: Such as thallium or arsenic.
• Severe protein-calorie malnutrition: Although less common as a direct cause, severe nutritional deficiencies can impact hair health.
• Autoimmune conditions: Certain severe autoimmune disorders, though rarer, can sometimes trigger anagen effluvium.

Chemotherapy-Induced Anagen Effluvium

Chemotherapy drugs interfere with the mitotic activity (cell division) of the hair matrix cells in the hair follicle. This disruption can occur in two main ways:

1. Dystrophic Anagen: The most common mechanism, where the chemotherapy drugs cause a dystrophic (abnormal and damaged) change within the hair follicle, leading to a weakened hair shaft that breaks easily at or near the scalp surface. The hair bulb may also be damaged.
2. Premature Catagen/Telogen: While less characteristic of pure anagen effluvium, some drugs can induce a rapid shift of anagen hairs into premature catagen and then telogen, leading to shedding.

The degree and speed of hair loss depend on the type, dose, and duration of the chemotherapy agents used. For instance, drugs like doxorubicin, cyclophosphamide, and paclitaxel are known to cause significant hair loss.

Symptoms and Diagnosis

The hallmark symptom of anagen effluvium is rapid, widespread hair shedding that typically begins within days to weeks of exposure to the causative agent, most notably after the first cycle of chemotherapy.

Key characteristics include:

• Diffuse Hair Loss: Affects the entire scalp, not just specific areas.
• Rapid Onset: Hair loss can be dramatic and quick.
• Scalp Involvement: Often involves the entire scalp, but can also affect eyebrows, eyelashes, and body hair.

---