Alopecia - Outlines in Clinical Medicine on Physicians' Online 2002
A. Definitions
Alopecia means hair loss
Androgenic alopecia - baldness caused by miniaturization of susceptible follicles
Alopecia areata - hair loss in patches believed to be autoimmune
Permanent alopecia - caused by destruction of hair follicles
Anagen Effluvium (see below)
Abrupt shedding of hair caused by interruption of active follicle growth
Cancer chemotherapy is most common cause
Telogen Effluvium (see below)
Excessive shedding of hair caused by increased proportion of follicles entering telogen
Drugs and fever are common causes
B. Scarring (Cicatricial) Alopecia (major causes only)
Inflammatory Dermatoses
Cicatricial pemphigoid
Lupus erythematosus - discoid and systemic
Necrobiosis lipoidica diabeticorum
Sarcoidosis
Scleroderma
Likely that most forms of alopecia have an autoimmune component
Infection
Bacterial - pyogenic, syphlis, tuberculosis, leprosy
Viral - herpes (varicella) zoster
Fungal and Protozoal infections
Physical and Chemical Agents
Neoplasms
Basal cell carcinoma
Lymphoma
Nevi and Melanoma
Metastatic Disease
Squamous cell carcinoma
Congenital Abnormalities
Aplasia cutis
Congenital ichthyosis
Epidermolysis bullosa
Hair follicle hamartoma
Ichthyosiform erythroderma
Keratosis pilaris atrophicans
C. Nonscarring Alopecia
Androgenic Alopecia [7]
Male common baldness
Affects ~65% of men
In women, often associated with acne, facial hirsutism (chronic anovulatory syndrome)
Common mechanism is androgen excess
Primary pathologic process due to androgen excess is called miniaturization
Miniaturization leads to conversion of large (terminal) hairs to small (vellus) hairs
Over time, the miniaturized hair follicles produce small, finer hairs
The number of follicles per unit of area remains the same
Young persons with androgenic alopecia have higher levels of 5alpha-reductase, more androgen receptors, and lower levels of P450 aromatase in frontal region hair follicles
Reducing androgen levels (dihydrotestosterone, DHT) can improve hair growth [3]
Telogen Effluvium
Diverse causes with anagen arrest
Hair loss (usually >50%) occurs 2-4 months after initiating event
Psychologic and pathologic causes and medications are often implicated
Drugs: anticoagulants, oral-contraceptive withdrawal, ß-blockers, tricyclics, ACE inhibitors, amphetamines, anti-thyroid medicines, lithium, levodopa, nicotinic acid
Other: hypothyroidism, fever, infection, severe systemic disease
Far more common than Anagen Effluvium
Anagen Effluvium
Drugs - colchicine, allopurinol, cimetidine, haloperidol, Vitamin A
Radiation and Chemotherapy
Heavy metal poisoning
Traumatic Alopecia
Trichotillomania - Nonscarring, patchy hair loss secondary to pulling out hair
Traction alopecia - tightly wound, braided hair
Alopecia Areata [7] See outline Lymphocytes
Autoimmune disease affecting ~2% of population in USA
Affects men and women equally
One or more asymptomatic circular to oval patches, usually sudden onset
May occur in small patches that regrow spontaneously, or persistent large patches
Atopy, vitiligo, and autoimmuen thyroid disease are more common in affected persons
Nail pitting is often present
Activated CD4+ and CD8+ T lymphocytes with reactivity to hair follicles are found
HLA-D (Class II MHC) associations have been observed
High levels of Tumor Necrosis Factor alpha (TNFa) have been found in lesions
Secondary syphilis
Congenital disorders
Many of these can eventually cause scarring
D. Treatments [7]
Finasteride [4] See outline Prostatic Hyperplasia
Reduction of DHT levels has been somewhat effective for androgenic alopecia [3]
Inhibitor of type 2 5-alpha-reductase (converts testosterone to DHT)
Finasteride (Propecia®), a 5-alpha reductase inhibitor, is FDA approved for hair growth
Finasteride, 1mg/day, reduces DHT levels ~65%, increases hair counts ~12%
Consider finasteride in women with polycystic ovary syndrome as well
Finasteride is contraindicated in women who may become or are pregnant
Minoxidil (Rogaine®) [5]
Induces and prolongs anagen stage, converts vellus to terminal follicles
Minoxidil is also an arteriolar vasodilator, can also improve hair counts slightly
5% and 2% solutions of minoxidil are FDA approved for promoting hair growth
Treatment requires 48 weeks or more for androgenic alopecia
Minoxidil (1 mL) is applied twice daily for effects
Side effects are irritation of the scalp including dryness
Hypertrichosis can occur in women using minoxidil
No effects on blood pressure are seen
Psoralen plus ultraviolat A (PUVA) has shown some efficacy [4]
Alopecia Areata
Glucocorticoids - topical or systemic See outline Glucocorticoids
Topical immunotherapy - induce contact sensitization
Anthrallin See outline Psoriasis
Minoxidil (see above)
Alopecia Totalis and Universalis
Relatively resistant to topical agents
PUVA has shown some activity but maintenance PUVA therapy required [4]
References
Nielsen TA and Reichel M. 1995. Am Fam Phys. 51(6):1513
Paus R and Cotsarelis G. 1999. NEJM. 341(7):491
Finasteride. 1998. Med Let. 40(1021):25
Weise K, Kretzschmar L, John SM, Hamma H. 1996. Dermatology. 192:129
Minoxidil. 1998. Med Let. 40(1021):26
Lebwohl M. 1997. Lancet. 349:222
Price VH. 1999. NEJM. 341(13):964