85: Androgenetic Alopecia Flashcards
(111 cards)
What is Androgenetic Alopecia (AGA)?
Androgenetic Alopecia (AGA) is the most common type of hair loss characterized by nonscarring progressive miniaturization of the hair follicle with shortening of the anagen phase in genetically predisposed men and women, typically following a specific pattern distribution.
What are the epidemiological factors associated with AGA?
The epidemiological factors associated with AGA include:
1. Onset at any age following puberty.
2. Increasing frequency with age:
- 50 y/o men: 50% to 60% affected.
- 70 y/o men: 80% affected.
3. Prevalence and severity are lower among Asians, Native Americans, and African Americans.
4. In Chinese men:
- 10% to 20% affected at ages 40-49.
- 40% to 60% affected by age 70 and beyond.
5. The frequency and severity is lower in women, appearing later in life, with 25% in Korean women and 12% to 15% in Chinese women over 70 y/o.
What are the clinical features of Male Pattern Hair Loss?
The clinical features of Male Pattern Hair Loss, specifically the Hamilton-Norwood type, include:
- Most frequent clinical pattern in men (occasionally in women).
- Characteristic finding: recession of the frontal hairline in a triangular pattern, followed by vertex thinning until the top of the scalp is completely bald.
- The occipital area and sides of the scalp are spared.
What are the characteristics of Female Pattern Hair Loss?
Female Pattern Hair Loss, specifically the Ludwig type, is characterized by:
- Diffuse thinning of the centroparetal region while maintaining the frontal hairline.
- It is the most common type of AGA in women (occasionally in men).
- There are two scales describing this pattern:
- 3-point Ludwig scale
- 5-point Sinclair scale.
What are the risk factors associated with Male AGA?
The risk factors associated with Male AGA include:
- Determined by genetic factors.
- Strong paternal influence on the risk of balding.
- Has a complex polygenic basis with 12 genetic regions associated with AGA as of the current writing.
What is the primary androgen responsible for follicular pathology in AGA?
Dihydrotestosterone is the androgen chiefly responsible for the follicular pathology in AGA, acting primarily on the dermal papilla.
What are some signaling molecules implicated in the inhibition of hair growth?
Signaling molecules include:
1. Transforming growth factor (TGF)-β1
2. Transforming growth factor (TGF)-β2
3. Dickkopf 1 (member of the WNT signaling family)
4. Interleukin-6
5. Prostaglandin D2 synthase and its product, prostaglandin D.
What should be documented in the patient history for diagnosing AGA?
The patient history should document:
- The first manifestation of hair loss and the course (chronic or intermittent)
- Family history of AGA
- Symptoms such as pruritus and trichodynia
- Any systemic diseases or nutritional behaviors prior to hair loss.
What are the key components of the clinical examination for AGA?
The clinical examination involves:
- Assessment of the scalp skin, hair, facial and body hair, and nails.
- Scalp examination to check for associated findings like seborrhea or seborrheic dermatitis.
What is the purpose of the hair pull test in diagnosing AGA?
The hair pull test (Sabouraud maneuver) is used to assess hair density and identify short and fine miniaturized hairs, helping to exclude scarring alopecia.
What are the key genetic factors associated with androgenetic alopecia (AGA) in men?
Key genetic factors include:
- Androgen receptor (AR)
- Histone deacetylases (HDAC) 4 and 9
- WNT molecule WNT10A
AGA is recognized as an androgen-dependent trait in men.
How does the clinical presentation of androgenetic alopecia differ between men and women?
In men, AGA typically presents as a longstanding, slowly progressing reduction of hair density, often with thinning at the frontal, parietal, or vertex regions. In women, the etiology is less understood, but there is an increased frequency of balding in first-degree male relatives, and hormonal dysregulation may play a role.
What are the important aspects to document in a patient’s history when diagnosing androgenetic alopecia?
Important aspects to document include:
1. Family history of hair loss
2. First manifestation of hair loss and its course (chronic or intermittent)
3. Duration and pattern of hair loss (e.g., frontal, parietal)
4. Symptoms such as pruritus and trichodynia
5. Gynecologic history in women, including menstrual cycle disturbances
6. Recent systemic diseases or significant weight loss
7. Environmental factors and hairstyles that may contribute to hair loss.
What clinical examination techniques are used to assess androgenetic alopecia?
Clinical examination techniques include:
- Scalp examination: Assessing the scalp skin, hair, and associated findings like seborrhea or dermatitis.
- Hair examination:
1. Parting hair to assess density
2. Comparing part width across different regions (frontal, occipital, temporal)
3. Dermoscopy/trichoscopy to evaluate hair follicle openings and identify miniaturized hairs
4. Hair pull test (Sabouraud maneuver) to assess hair loss.
What is the significance of a positive pull test in diagnosing hair shedding?
A positive pull test indicates that more than 10% of the grasped hairs are pulled away, confirming active hair shedding. It may be positive in the frontal region but typically negative in the occipital region.
What are the peripheral signs of hyperandrogenism that may be observed in patients?
Peripheral signs of hyperandrogenism include:
- Acne
- Seborrhea
- Oily skin
- Obesity.
What role does dermoscopy play in the examination of AGA?
Dermoscopy is a noninvasive tool that improves the examination of scalp skin and hair shafts by magnification. In AGA, it helps assess hair follicle openings, hair shaft caliber variations, and can reveal hair diameter variations and an increased number of vellus hairs.
What findings in AGA can be observed through a phototrichogram?
Findings in AGA observed through a phototrichogram include:
- Reduced hair density in a pattern distribution compared to the occipital area.
- Anagen-to-Telogen ratio is normal or decreased when comparing frontal or vertex to the occiput.
When is a biopsy indicated in the diagnosis of AGA?
A biopsy is indicated when the diagnosis is uncertain. It is performed as a deep, 4-mm cylindrical punch and evaluated by dermatopathologists using both vertical and horizontal sectioning.
What laboratory tests are associated with AGA in men?
Laboratory testing for AGA in men is generally not necessary unless there is an underlying disorder or associated disease. However, there are possible positive associations with:
- Insulin resistance
- Metabolic syndrome
- Hypertension
- Benign prostate hyperplasia
Additionally, measurement of the prostate-specific antigen value is recommended before introducing finasteride therapy.
What diagnostic tools can confirm androgenetic alopecia (AGA) and differentiate it from other conditions?
Diagnostic tools include dermoscopy to assess hair follicle openings and hair shaft caliber variations, global photography for long-term follow-up, and phototrichogram to measure hair density and anagen-to-telogen ratio. A biopsy may be performed if the diagnosis is uncertain.
What histological findings are characteristic of AGA?
Findings include increased miniaturized (vellus-like) hair follicles, a terminal-to-vellus hair ratio of <3:1, increased telogen-to-anagen ratio, and mild perifollicular lymphohistiocytic infiltration.
What precaution should be taken before starting finasteride in a male patient with AGA and a family history of prostate cancer?
The prostate-specific antigen value should be measured before introducing finasteride therapy.
What is the preferred biopsy site for AGA, and why?
The central scalp is preferred as it is representative of the hair loss process. The bitemporal area should be avoided due to the presence of miniaturized hairs independent of AGA.
