Telogen Effluvium - Dermatology Notes

Definition: A non-scarring alopecia characterized by a shift of a large number of hair follicles from the anagen (growth) phase into the telogen (resting) phase, resulting in diffuse, synchronous shedding 2–3 months after a physiological or emotional trigger.

Key Clinical Features:

• Acute telogen effluvium: Sudden onset of diffuse hair shedding, typically 2–3 months (8–12 weeks) after a triggering event. Shedding lasts less than 6 months.

• Chronic telogen effluvium: Persistent shedding for more than 6 months (often years); may have no identifiable trigger; tends to affect middle-aged women (30–60 years).

• Presentation: Patient complains of excessive hair loss on the pillow, in the shower, or on the hairbrush. Often described as "clumps of hair falling out."

• Distribution: Diffuse throughout the scalp; no discrete patches of alopecia. Bitemporal and vertex regions are most noticeable but the entire scalp is involved.

• Hair pull test: Positive – more than 3–5 telogen hairs are extracted with gentle traction. Hairs are telogen hairs (white bulb at the proximal end, no gelatinous root sheath).

• Scalp examination: No inflammation, no scarring, no erythema, no follicular dropout.

• Part width: Normal or mildly widened (but no complete bald spots).

• Pattern: Frontal and temporal hairline is usually preserved (unlike androgenetic alopecia which shows bitemporal recession).

• Symptom: Shedding is often more noticeable to the patient than to the examiner because density may still appear normal.

Triggers for Acute Telogen Effluvium (must know for boards):

Under physiological stress triggers: high fever, severe illness, major surgery, hospitalization, and childbirth (postpartum telogen effluvium – occurs 2–3 months after delivery).

Under psychological stress triggers: emotional trauma, death of a loved one, divorce, and severe anxiety.

Under nutritional triggers: crash dieting, rapid weight loss, low protein intake, iron deficiency (controversial – more associated with chronic TE), and zinc deficiency.

Under endocrine triggers: hypothyroidism, hyperthyroidism, discontinuation of oral contraceptives, and the postpartum state.

Under drug triggers: retinoids (acitretin, isotretinoin), anticoagulants, beta-blockers, anticonvulsants (valproate), antidepressants (SSRIs), lithium, interferons, and androgens or anabolic steroids.

Under metabolic triggers: severe iron deficiency anemia, chronic renal failure, and liver disease.

Under inflammatory triggers: systemic lupus erythematosus (non-scarring telogen effluvium can precede scarring alopecia).

Chronic Telogen Effluvium Triggers:

• Often idiopathic (no identifiable trigger).

• Chronic iron deficiency (ferritin less than 40 ng/mL) – controversial; many experts do not consider mild iron deficiency a cause.

• Chronic low-grade illness such as autoimmune thyroiditis or inflammatory bowel disease.

• Chronic drug use including long-term retinoids or oral contraceptives.

• Persistent psychological stress.

Associated Conditions/Diseases:

• Postpartum telogen effluvium: Occurs 2–3 months after delivery; typically self-limited over 3–6 months.

• Loose anagen syndrome: Children (blonde hair), hairs pulled out easily with a gelatinous root sheath; differs from TE (in TE, pulled hairs have white bulbs without sheath).

• Anagen effluvium: Caused by chemotherapy (antimitotic drugs); shedding occurs days to weeks after exposure, not months.

• Androgenetic alopecia: Can coexist with chronic TE (telogen effluvium unmasks underlying genetic thinning).

Prognosis:

• Acute telogen effluvium: Excellent – complete recovery within 3–6 months after trigger removal. Hair density returns to baseline.

• Chronic telogen effluvium: Variable – may persist for years; often does not progress to baldness; hair density may be mildly reduced but not severely. Spontaneous remission can occur.

Differential Diagnosis:

• Androgenetic alopecia (AGA): Bitemporal recession, vertex thinning, miniaturized hairs on trichoscopy (hair diameter diversity greater than 20%), positive family history, no acute trigger.

• Chronic telogen effluvium: Diffuse shedding, normal hair shaft diameter, no miniaturization, preserved frontal hairline, female predominance.

• Alopecia areata incognita (diffuse alopecia areata): Acute diffuse shedding, positive hair pull test with dystrophic anagen hairs (exclamation mark hairs, tapered hairs), trichoscopy shows yellow dots, black dots, and broken hairs.

• Anagen effluvium: Chemotherapy or radiation exposure days to weeks prior; shedding is rapid and severe; hairs have tapered, broken, or dystrophic anagen roots.

• Loose anagen syndrome: Children (especially girls with blonde hair), hairs extracted painlessly with a gelatinous root sheath, no trigger.

• Thyroid disease (hypo or hyper): Diffuse shedding; confirm with TSH and free T4.

• Iron deficiency anemia: Diffuse shedding; confirm with ferritin and CBC.

• Systemic lupus erythematosus (non-scarring): Diffuse shedding; may have other cutaneous or systemic features; positive ANA.

Management with Rationale:

• Identify and remove trigger (most important): Discontinue offending drug; treat underlying thyroid disease; correct iron deficiency; manage stress; improve nutrition.

• Reassurance: Acute TE is self-limited; hair will regrow within 3–6 months. Chronic TE may wax and wane but rarely causes baldness.

• Minoxidil (topical 2% or 5%): For chronic telogen effluvium or when shedding is distressing. Rationale: prolongs anagen and shortens telogen; reduces shedding after 3–4 months of use.

• Nutritional supplementation: Correct iron deficiency (ferritin target greater than 40–70 ng/mL); zinc supplementation if deficient; biotin (weak evidence, but commonly used).

• Corticosteroids: NOT indicated for telogen effluvium (used for alopecia areata and scarring alopecias).

• Hair care counseling: Gentle handling, avoid tight hairstyles, avoid harsh chemicals.

• No laboratory testing if classic acute TE with clear trigger – testing is reserved for chronic TE or when trigger is unclear.

Rationale for no treatment in acute TE: The condition is self-limited; treatment does not accelerate recovery. Minoxidil may be used for patient comfort but does not shorten the duration.

Histopathology (Structured as requested)

1. FOUNDATIONS (First Principles)

• Normal hair cycle:

  • Anagen (growth phase): 85–90% of scalp hairs; lasts 2–6 years. Hair bulb is deeply seated in subcutis; melanocytes active; matrix keratinocytes proliferate rapidly.

  • Catagen (regression phase): 1–2% of hairs; lasts 2–3 weeks. Apoptosis of follicular keratinocytes; hair bulb retracts upward.

  • Telogen (resting phase): 10–15% of hairs; lasts 3–4 months. Hair bulb is at the level of the isthmus (upper dermis); club hair is formed; no melanogenesis.

  • Exogen (shedding phase): Active release of club hair; formerly considered part of telogen.

• Normal telogen hair count: 10–15% of scalp hairs. In telogen effluvium, this increases to 20–50%.

• Normal anagen to telogen ratio: 85:15. In acute TE, the ratio shifts to 70:30 or lower.

2. INITIATING EVENT

• Acute TE: A trigger (fever, surgery, childbirth, drug, stress) causes premature termination of anagen in a large number of follicles that would otherwise have continued growing for months to years.

• Mechanism: The trigger likely acts via corticotropin-releasing hormone (CRH) and substance P released from cutaneous nerve endings, which activates mast cells and perifollicular macrophages, leading to release of cytokines (IL-1, IL-6, TNF). These cytokines induce keratinocyte apoptosis and premature catagen entry.

• Alternatively (older theory): The trigger causes a sudden shift of anagen follicles into telogen without going through a prolonged catagen. This is now considered less likely; catagen is accelerated, not skipped.

3. PATHOGENESIS (Cause → Effect Chain)

• A trigger such as high fever leads to a systemic inflammatory response, causing cytokine release (IL-1, TNF) into the dermis.

• IL-1 acts directly on hair follicle keratinocytes via the IL-1 receptor, inhibiting proliferation in the hair matrix and inducing premature apoptosis.

• Follicles that are in mid-to-late anagen are most sensitive (early anagen is resistant).

• There is accelerated transition from anagen to catagen, occurring within days to weeks instead of the normal gradual transition.

• Catagen is shortened, and follicles quickly enter telogen.

• During telogen (lasting 3–4 months), the club hair remains anchored in the follicle.

• At the end of telogen, the club hair is shed (exogen). Because many follicles entered telogen synchronously around the same time, shedding also occurs synchronously.

• Why the 2–3 month delay? The time from premature catagen induction to exogen (shedding) is approximately 8–12 weeks, which is the combined duration of catagen plus telogen.

• Chronic TE: A persistent low-grade trigger (such as chronic stress, nutritional deficiency, or thyroid disease) leads to a continuous shift of anagen follicles into telogen, resulting in a sustained increase in telogen count without a single massive synchronous shed.

4. HISTOPATHOLOGY EXPLAINED (CRITICAL)

Low power (horizontal sections – preferred for hair disorders):

• There is a decreased anagen to telogen ratio, meaning an increased number of telogen follicles exceeding 20% (normal is 15% or less). This is assessed by counting 50–100 follicles in horizontal section.

• Telogen follicle morphology shows a small, non-pigmented, shallow follicle. The hair bulb is at the level of the isthmus (upper dermis, just below the sebaceous gland). No hair shaft is seen emerging from the follicle because the club hair is retained.

• Anagen follicle morphology shows a large, deeply seated follicle (in the subcutis), a pigmented bulb, surrounded by a thick dermal papilla and fibrous root sheath.

• There is no inflammation (perifollicular inflammation is absent – a key discriminator from alopecia areata and scarring alopecias).

• There is no fibrosis (no scarring).

• There is no miniaturization – all follicles are of normal size (in androgenetic alopecia, miniaturized follicles with smaller diameters are seen).

High power:

• The telogen club hair shows a proximal end that is a club-shaped, keratinized, unpigmented bulb with no melanocytes and no matrix. It is surrounded by a trichilemmal keratinized layer.

• There is no inner or outer root sheath in the lower follicle because these have regressed.

• There are no mitotic figures in telogen follicles (mitoses are present only in anagen matrix).

• The dermal papilla is small, condensed, and sits immediately below the club hair (not enveloped by matrix as in anagen).

• Sebaceous glands are of normal size and number (preserved in TE; in androgenetic alopecia, sebaceous glands may appear relatively enlarged due to follicular miniaturization).

Horizontal section diagnostic criteria (board essential):

• Telogen count exceeds 20% of total follicles (normal is 15% or less).

• Anagen count is less than 80% (normal is 85–90%).

• The anagen to telogen ratio is less than 4:1 (normal is 5–6:1).

• There is no increase in catagen follicles (catagen is transient; in TE, follicles rapidly transit catagen, so catagen counts are normal or low).

Why this appearance:

• Increased telogen follicles occur because the pathogenesis is exactly this: too many follicles are in telogen.

• No inflammation because TE is not an inflammatory alopecia. The trigger acts systemically, not via local lymphocytic attack on follicles.

• No miniaturization because the follicle itself is normal; the problem is the cycling, not the follicle size.

• Normal sebaceous glands differ from androgenetic alopecia, where sebaceous glands appear prominent because follicles shrink around them.

Vertical sections (less informative for TE but may be used):

• Vertical sections show a normal epidermis and dermis.

• Telogen follicles appear as small, epithelial strands extending from the isthmus to a small bulb in the upper dermis.

• There is no inflammation and no fibrosis.

5. NAMING LOGIC & TERMINOLOGY

• Telogen – From Greek telos meaning end plus gen meaning produce – the resting or end phase of the hair cycle.

• Effluvium – From Latin effluere meaning to flow out – refers to the shedding or outflow of hair.

• Acute – Sudden onset, duration less than 6 months.

• Chronic – Persisting beyond 6 months.

• Club hair – The proximal end of a telogen hair is club-shaped (rounded, keratinized, and unpigmented).

• Anagen to telogen ratio – Quantitative measure of cycling status.

6. STAINING & MARKERS

• H&E of horizontal sections is the gold standard for histopathologic diagnosis of hair disorders.

• Trichrome stain (Masson's trichrome) is not needed for TE but can highlight follicular fibrosis (absent in TE).

• Immunohistochemistry (not diagnostic, research only):

  • Ki-67 (MIB-1) shows low or absent staining in telogen follicles (no proliferation) and high staining in anagen follicles (matrix keratinocytes).

  • TUNEL assay shows increased apoptotic cells in catagen follicles (in TE, apoptosis is accelerated but occurs during catagen, not visible at the time of biopsy unless biopsied in the acute phase – which is rare).

  • Caspase-3 is positive in catagen follicles as an apoptosis marker.

  • CD3, CD4, and CD8 show no significant lymphocytic infiltrate (differentiates from alopecia areata, which has peribulbar lymphocytes).

• Hair pull test (clinical, not histology): Microscopic examination of pulled hairs. Telogen hairs have a white, club-shaped bulb with no root sheath. Anagen hairs have a pigmented, elongated, frayed bulb with a gelatinous root sheath.

7. TEMPORAL EVOLUTION

• Immediate post-trigger period (days to weeks): There is no visible shedding. Histology (if performed – rarely) shows increased catagen follicles (the transition phase). This is not clinically useful because biopsy is rarely done this early.

• 2–3 months after trigger (peak shedding): Histology shows increased telogen follicles exceeding 20%. This is the diagnostic window. The patient presents with active shedding.

• 3–6 months after trigger (recovery): Anagen follicles re-enter growth phase. Telogen count gradually returns to normal. Histology shows a mix of new anagen follicles (small, early anagen with small bulbs) and telogen follicles.

• 6 or more months (chronic TE): There is persistent telogen count exceeding 20% without a single identifiable trigger. Histology shows no inflammation, no miniaturization, and normal sebaceous glands. This is a diagnosis of exclusion.

8. PATTERN RECOGNITION & DIAGNOSTIC LOGIC

• Pattern (horizontal sections): Increased telogen count (exceeding 20%) plus normal follicle size plus no inflammation plus no fibrosis plus preserved sebaceous glands.

Diagnostic pathway (histologic, integrating clinical history):

• If there is increased telogen count with a clear trigger 2–3 months prior and self-limited shedding lasting less than 6 months, then diagnose acute telogen effluvium. A biopsy is usually not needed; biopsy confirms if diagnosis is uncertain.

• If there is increased telogen count with no identifiable trigger and shedding lasting more than 6 months with no miniaturization, then diagnose chronic telogen effluvium. This is a diagnosis of exclusion; biopsy is essential to rule out early androgenetic alopecia or diffuse alopecia areata.

• If there is increased telogen count with miniaturization (hair diameter diversity) and preserved sebaceous glands, then diagnose androgenetic alopecia with telogen effluvium (both conditions coexist – very common).

• If there is increased telogen count with peribulbar lymphocytic infiltrate (swarm of bees) and increased catagen to telogen ratio, then diagnose alopecia areata (diffuse variant – alopecia areata incognita).

• If there is increased telogen count with perifollicular fibrosis and follicular dropout, then diagnose early scarring alopecia (lichen planopilaris, frontal fibrosing alopecia).

Key discriminator from androgenetic alopecia on histology:

• Telogen effluvium shows all follicles of uniform, normal size; the anagen to telogen ratio is decreased but follicles are not miniaturized.

• Androgenetic alopecia shows miniaturized follicles (terminal to vellus-like conversion); increased telogen count may also be present; sebaceous glands appear relatively enlarged.

Key discriminator from alopecia areata on histology:

• Telogen effluvium shows no peribulbar inflammation.

• Alopecia areata shows peribulbar lymphocytic infiltrate (swarm of bees), increased catagen follicles, pigment incontinence, and eosinophils may be present.

9. CLINICO-PATHOLOGICAL CORRELATION

• Diffuse hair shedding corresponds to increased telogen count, meaning more hairs are ready to be shed (exogen).

• Positive hair pull test occurs because gentle traction extracts telogen hairs (club hairs) that are loosely anchored.

• No bald patches occurs because shedding is diffuse; no follicle is permanently lost; density is reduced but not to the point of complete baldness because some anagen follicles remain.

• Preserved frontal hairline – In TE, the frontal hairline is maintained; in androgenetic alopecia, the frontal hairline recedes (in men) or shows widening of the part (in women).

• Normal scalp appearance reflects no inflammation, no erythema, and no scaling (unlike seborrheic dermatitis, psoriasis, or scarring alopecia).

• Shedding more noticeable to patient than examiner – Normal hair density is 100,000 to 150,000 hairs; losing 200–300 hairs per day (instead of 50–100) may not be visually obvious but is distressing to the patient.

• Postpartum TE is triggered by the hormonal shift after delivery (drop in estrogen, which prolongs anagen). It occurs 2–3 months postpartum and typically resolves by 6–9 months postpartum.

10. EXAM-FOCUSED INSIGHTS

• Timing is diagnostic – Shedding 2–3 months after a trigger indicates acute TE. Shedding within days to weeks of a trigger indicates anagen effluvium (chemotherapy, radiation).

• Hair pull test is an essential clinical skill. Pull 40–60 hairs gently; count extracted hairs. More than 3–5 telogen hairs is positive. Examine extracted hairs under a microscope or against a dark background: a white bulb indicates telogen; a pigmented bulb indicates anagen.

• Postpartum TE is the most common form of TE – Affects 40–50% of women. Onset at 8–12 weeks postpartum. Can be mistaken for postpartum thyroiditis (check TSH if prolonged).

• Chronic TE is a diagnosis of exclusion – Must rule out androgenetic alopecia, thyroid disease, iron deficiency, and diffuse alopecia areata.

• Biopsy is rarely needed for acute TE – Diagnosis is clinical. Biopsy is indicated when shedding persists beyond 6 months, when the trigger is unclear, when alopecia areata or scarring alopecia is suspected, or when the patient has signs of inflammation or scarring.

• Horizontal sectioning is superior to vertical – Horizontal sections allow counting of anagen versus telogen follicles and assessment of miniaturization. If the laboratory only performs vertical sections, the diagnosis of TE may be missed.

• Normal telogen count is 15% or less – Values of 20–30% are diagnostic of TE; values exceeding 30% indicate severe TE.

• Minoxidil is not first-line for acute TE – It may reduce shedding but does not shorten the duration. It is used for chronic TE or for patient reassurance.

• Iron deficiency as a cause of TE is controversial – Many studies show no correlation. However, it is common to check ferritin. Target ferritin greater than 40 ng/mL if supplementing.

• Do NOT biopsy a patient with classic acute TE – It is unnecessary, invasive, and may show only normal histology if biopsied too early or too late. Biopsy at peak shedding (2–3 months post-trigger) shows increased telogen.

• Drug-induced TE – The most common drugs are retinoids, anticoagulants, beta-blockers, interferons, and antithyroid drugs. Onset is 2–3 months after starting the drug.

Must-Know Board Exam Questions & Answers

Q1: A 28-year-old woman presents with diffuse hair shedding that began 10 weeks after giving birth to a healthy infant. Hair pull test shows 8 telogen hairs. Scalp examination is normal. What is the most likely diagnosis?

A: Postpartum telogen effluvium (acute telogen effluvium).

Q2: What is the expected time interval between a triggering event and the onset of hair shedding in acute telogen effluvium?

A: 8 to 12 weeks (2–3 months).

Q3: A patient complains of excessive hair shedding for 18 months. Scalp biopsy with horizontal sections shows 25% telogen follicles, no miniaturization, no inflammation, and normal sebaceous glands. What is the diagnosis?

A: Chronic telogen effluvium.

Q4: What is the histologic finding that distinguishes chronic telogen effluvium from early androgenetic alopecia?

A: Telogen effluvium shows no miniaturization (all follicles are of normal, uniform size). Androgenetic alopecia shows miniaturized follicles (hair diameter diversity greater than 20%).

Q5: A patient undergoing chemotherapy develops severe hair shedding 3 weeks after the first cycle. What type of effluvium is this, and why is the timing different from telogen effluvium?

A: Anagen effluvium. Chemotherapy targets rapidly dividing matrix keratinocytes, causing immediate anagen arrest and shedding within days to weeks, not months.

Q6: What is the normal percentage of telogen hairs on scalp histology (horizontal section)?

A: 15% or less (10–15% is normal). In telogen effluvium, telogen count exceeds 20%.

Q7: A hair pull test yields several hairs. Microscopic examination shows hairs with a white, club-shaped bulb and no root sheath. Are these anagen or telogen hairs?

A: Telogen hairs (club hairs). Anagen hairs have a pigmented, elongated, frayed bulb with a gelatinous root sheath.

Q8: Name four common triggers of acute telogen effluvium.

A: High fever (severe illness), major surgery, childbirth (postpartum), and rapid weight loss (crash dieting). Also accepted: emotional stress, hypothyroidism, and drugs including retinoids, anticoagulants, and beta-blockers.

Q9: Is a scalp biopsy indicated for classic acute telogen effluvium with a clear trigger?

A: No. The diagnosis is clinical. Biopsy is reserved for chronic shedding (more than 6 months), unclear trigger, or suspected alopecia areata or scarring alopecia.

Q10: What is the histologic finding in telogen effluvium that is never seen in androgenetic alopecia?

A: No single finding is never seen; however, the absence of miniaturization is the key discriminator. Telogen effluvium has normal-sized follicles; androgenetic alopecia has miniaturized follicles.