One of the most common causes of male baldness universally is a disorder known as androgenetic alopecia (AGA), which induces a visible hairline recession. This form of hair loss is estimated to affect more than 50 million men and 30 million women in the United States, alone.
Androgenetic alopecia is characterized by a progressive loss of hair and miniaturization of the hair follicle responsible for new hair growth. The etiology behind the disorder is proposed to be multifactorial, including genetics, hormonal imbalances, receptor abnormalities, stress, and practicing an unhealthy lifestyle.
This type of patterned hair loss is observed in both genders and frequently occurs after the onset of puberty. However, unlike men, women demonstrate a more preserved frontal hairline that is accompanied by diffuse thinning of the hair in the front and sides of the scalp. The hair on the back of the scalp is generally spared in females. The condition rarely leads to complete baldness in females. Therefore, for the current discussion androgenetic alopecia in only men would be categorized into different types based on hairline recession.
Types of hairline recession in Androgenetic Alopecia
A wide variety of hairline recession may be observed in the population suffering from androgenetic alopecia. Several classifications have been proposed over decades to categorize these different types of hairline recession, however, the most commonly employed is the Basic and Specific (BASP) classification that was first introduced by Lee et al. in 2007. BSAP classification is a comprehensive tool that is both used clinically and for research on androgenetic alopecia.
The BASP classification
BSAP classification includes four basic and two specific types of hairline recession observed in patients with androgenetic alopecia. The basic type generally represents the shape of the frontal hairline and the specific type is used to describe the density of hair present on the front and the topmost area of the head. Both the basic and the specific types can be further divided into three to four grades that define their severity.
The basic type is used to represent the shape of the anterior hairline and is subdivided into four types.
1. Type L (or linear)
Type “L” refers to a straight hairline that can be appreciated when no hair loss occurs along the anterior border.
2. Type M
In this type, the recession of the frontal hairline is much prominent and resembles the formation of the letter M. This type is further divided into 4 grades M0, M1, M2, M3, and M4 depending upon the degree of hairline and top of the head(vertex) involved.
3. Type C
Here the recession of the hairline is more concentrated towards the midline, relatively less involving the sides. The resultant hairline thus forms a semicircle resembling the letter “C”. Similar to the M type, the type C can also be subdivided into 4 grades depending upon the severity of hair loss.
4. Type U
The last type U is apparent when the frontal hairline recedes posteriorly even beyond the center of the midline, unlike type C. The result is a horseshoe-shaped hairline that resembles the letter “U”. This is the most severe type of androgenetic alopecia seen. There are four more grades to this type.
Two specific types define the degree of hair thinning and may be included whenever found necessary:
1. Type F
Type F is used to represent a general decrease in the density of hair over the entire top of the scalp, regardless of the anterior hairline shape. It is further divided into 3 subtypes F1, F2, F3 depending upon the mild, moderate, and severe hair loss observed, respectively.
2. Type V
Type V comments upon the degree of thinning of the hair observed on the top of the head (vertex). With V1, V2, and V3 further representing the mild, moderate, and severe thinning of hair on the vertex, respectively.
1. Lolli F, Pallotti F, Rossi A, Fortuna MC, Caro G, Lenzi A, Sansone A, Lombardo F. Androgenetic alopecia: a review. Endocrine. 2017 Jul 1;57(1):9-17.
2. Alfonso M, Richter-Appelt H, Tosti A, Viera MS, García M. The psychosocial impact of hair loss among men: a multinational European study. Current medical research and opinion. 2005 Nov 1;21(11):1829-36.
3. Salman KE, Altunay IK, Kucukunal NA, Cerman AA. Frequency, severity and related factors of androgenetic alopecia in dermatology outpatient clinic: a hospital-based cross-sectional study in Turkey. Anais Brasileiros de dermatologia. 2017 Feb;92(1):35-40.
4. Lee WS, Ro BI, Hong SP, Bak H, Sim WY, Park JK, Ihm CW, Eun HC, Kwon OS, Choi GS, Kye YC. A new classification of pattern hair loss that is universal for men and women: basic and specific (BASP) classification. Journal of the American Academy of Dermatology. 2007 Jul 1;57(1):37-46.
5. Olsen EA. Current and novel methods for assessing the efficacy of hair growth promoters in pattern hair loss. Journal of the American Academy of Dermatology. 2003 Feb 1;48(2):253-62.
6. Ludwig E. Classification of the types of androgenetic alopecia (common baldness) occurring in
the female sex. British Journal of Dermatology. 1977 Sep;97(3):247-54.
7. Koo SH, Chung HS, Yoon ES, Park SH. A new classification of male pattern baldness and a
clinical study of the anterior hairline. Aesthetic plastic surgery. 2000 Jan 1;24(1):46-51.
8. Birch MP, Lalla SC, Messenger AG. Female pattern hair loss. Clinical and Experimental
Dermatology: Clinical dermatology. 2002 Jul;27(5):383-8.
9. Kim BJ, Choi J, Choe SJ, Lee S, Lee WS. Modified basic and specific (BASP) classification for
pattern hair loss. International Journal of Dermatology. 2020 Jan;59(1):60-5.
10. Agarwal S, Godse K, Mahajan A, Patil S, Nadkarni N. Application of the basic and specific classification on patterned hair loss in Indians. International journal of trichology. 2013 Jul
11. Qu Q, Miao Y, Guo ZH, Feng CB, Chen Q, Liu Y, Liu F, Shi PL, Cao DX, Hu ZQ. Types of hairline
recession in androgenetic alopecia and perceptions of aging in Asian males. International journal
of dermatology. 2019 Oct;58(10):1191-6.
12. Gupta M, Mysore V. Classifications of patterned hair loss: a review. Journal of cutaneous and
aesthetic surgery. 2016 Jan;9(1):3.