DEFINITION
Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body
EPIDEMIOLOGY
age, sex, seasonality, etc
SYMPTOMS
DIAGNOSIS
histopathology
radiology
NMR
laboratory tests
PATHOGENESIS
PATIENT RISK FACTORS
Vascular
Genetic
Acquired
Hormonal
Genetic
Different levels of 5alpha-reductase type I and II, aromatase, and androgen receptor in hair follicles of women and men with androgenetic alopecia. 1997
J Invest Dermatol. 1997 Sep;109(3):296-300.
Sawaya ME, Price VH.
Department of Medicine, University of Florida, Gainesville 32610, U.S.A.
In this study, 12 women and 12 men, ages 18-33 y, with androgenetic alopecia were selected for biopsies from frontal and occipital scalp sites. The androgen receptor, type I and II 5alpha-reductase, cytochrome P-450-aromatase enzyme were measured and analyzed in hair follicles from these scalp biopsies. Findings revealed that both women and men have higher levels of receptors and 5alpha-reductase type I and II in frontal hair follices than in occipital follicles, whereas higher levels of aromatase were found in their occipital follicles. There are marked quantitative differences in levels of androgen receptors and the three enzymes, which we find to be primarily in the outer root sheath of the hair follicles in the two genders. Androgen receptor content in female frontal hair follicles was approximately 40% lower than in male frontal hair follicle. Cytochrome P-450-aromatase content in women's frontal hair follicles was six times greater than in frontal hair follicles in men. Frontal hair follicles in women had 3 and 3.5 times less 5alpha-reductase type I and II, respectively, than frontal hair follicles in men. These differences in levels of androgen receptor and steroid-converting enzymes may account for the different clinical presentations of androgenetic alopecia in women and men.
Acquired
Skin disorders and thyroid diseases.
TISSUE SPECIFIC RISK FACTORS
anatomical (due its structure)
vascular (due to the local circulation)
physiopathological (due to tissue function and activity)
Cadherin 23 is a component of the tip link in hair-cell stereocilia
RXR-alpha ablation in skin keratinocytes results in alopecia and epidermal alterations. 2001
Interactions of the vitamin D receptor with the corepressor hairless: analysis of hairless mutants in atrichia with papular lesions. 2007
A novel missense mutation in the mouse hairless gene causes irreversible hair loss: genetic and molecular analyses of Hr m1Enu. 2006
- Abstract
A novel autosomal recessive mutant was produced using N-ethyl-N-nitrosourea mutagenesis. The characteristics of the mutant mice included progressive irreversible hair loss within a month of birth, wrinkled skin, and long curved nails. Linkage analysis revealed that the causative gene is linked to D14Mit193 on chromosome 14. Sequence analysis of the complete cDNA of the candidate gene, hairless (Hr), identified a homozygous G-to-T transition at nucleotide 3572, leading to the substitution of glycine by tryptophan, designated Gly960Trp. This missense mutation occurs in the vicinity of repression domain 3 of the hairless protein (HR). This allele was named Hr(m1Enu). The relative amounts of Hr mRNA and HR protein determined by real-time PCR and Western blot analyses, respectively, were slightly elevated in the mutant mice. Quantitative real-time PCR analysis revealed the increased expression of Kc1 and Vdr in the mutant mice, whereas the expression of Nrs1 and Krtap16-6 was decreased. These results suggest that the Gly960Trp substitution in HR protein in Hr(m1Enu) mice may alter the function of HR as a transcriptional corepressor.
COMPLICATIONS
THERAPY
Cadherin 23 is a component of the tip link in hair-cell stereocilia
RXR-alpha ablation in skin keratinocytes results in alopecia and epidermal alterations. 2001
Interactions of the vitamin D receptor with the corepressor hairless: analysis of hairless mutants in atrichia with papular lesions. 2007
m
Comorbidity profiles among patients with alopecia areata: The importance of onset age, a nationwide population-based study. 2011
Department of Dermatology, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Dermatology, National Yang-Ming University, Taipei, Taiwan.
Abstract
BACKGROUND:
Alopecia areata (AA) is considered an autoimmune disease with undetermined pathogenesis. Age at onset predicts distinct outcomes. A nationwide study of the relationship of AA with associated diseases stratified by onset age has rarely been reported.
OBJECTIVE:
We sought to clarify the role of atopic and autoimmune diseases in AA, thereby better understanding its pathogenesis.
METHODS:
A total of 4334 patients with AA were identified from the National Health Insurance Database in Taiwan from 1996 to 2008. A national representative cohort of 784,158 persons served as control subjects.
RESULTS:
Among patients with AA, there were significant associations with vitiligo, lupus erythematosus, psoriasis, atopic dermatitis, autoimmune thyroid disease, and allergic rhinitis. Different ages at onset resulted in disparate comorbidities. Increased risk of atopic dermatitis (odds ratio [OR] 3.82, 95% confidence interval 2.67-5.45) and lupus erythematosus (OR 9.76, 95% confidence interval 3.05-31.21) were found in childhood AA younger than 10 years. Additional diseases including psoriasis (OR 2.43) and rheumatoid arthritis (OR 2.57) appeared at onset age 11 to 20 years. Most atopic and autoimmune diseases were observed at onset ages of 21 to 60 years. With onset age older than 60 years, thyroid disease (OR 2.52) was highly related to AA. Moreover, patients with AA had higher risk for more coexisting diseases than control subjects.
LIMITATIONS:
We could not differentiate hypothyroidism from hyperthyroidism.
CONCLUSIONS:
AA is related to various atopic and autoimmune diseases. Different associated diseases in each onset age group of AA can allow clinician to efficiently investigate specific comorbidities.