Abstract
Introduction
Alopecia areata (AA) is a common non-scaring hair loss disease. Genetic susceptibility and environmental factors can develop the disease.
Objectives
We investigated the association between AA and ABO and Rh blood groups.
Methods
This cross-sectional study was done on 200 patients with AA and 200 healthy controls (HCs) between March 2021 and September 2021.
Results
The prevalence of blood groups O, A, B, and AB in patients with AA was 30%, 30.5%, 10.5%, and 29%, respectively. A significant difference was detected between the two groups in the frequency of the ABO and ABO*Rh blood groups (p-value < 0.05). Compared to the HCs, the prevalence of the AB and AB+ blood group was higher in AA patients. No significant relationship was detected between sex, BMI, duration of disease, age at onset, severity of alopecia tool (SALT) score, hair loss pattern, and nail involvement with ABO and Rh blood groups (p-value > 0.05).
Conclusion
In conclusion, the highest difference was related to the AB+ blood group, so compared to HCs, the AB+ blood group frequency was higher in patients with AA. However, more studies with larger sample sizes on different ethnicities should be performed to verify the results of this study.
Keywords: alopecia areata, blood group, ABO, Rh
Introduction
Alopecia areata (AA) is a common non-scaring hair loss disorder. The prevalence of the disease is 1 in 1000 cases and has a lifetime incidence of 2% [1]. The prevalence of the disorders indicated above is expected to be roughly 0.2 percent in the overall population. Moreover, genetic susceptibility and environmental factors can also induce the disease to develop [2]. However, the specific cause of the disease is unidentified. There are several lines of evidence linking AA to autoimmune diseases, like type 1 diabetes mellitus (DM), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), vitiligo, and pemphigus Vulgaris [3–6].
Human gene variation, such as HLA systems, is defined by red cell isoenzymes, blood groups, hemoglobin variations, and serum proteins [7]. The ABO blood group system includes four O, A, B, and AB common blood groups. The presence of specific carbohydrate sugars on the surface of red blood cells distinguishes these different blood groups. A is identified by N-acetylgalactosamine, and B is identified as D-galactose for the B antigen. These sugars can be built on the H antigen, and in cases of the unmodified H antigen, the blood group will be O since the A and B antigens are unable to adhere to the surface of red blood cells [7]. The Rhesus blood group system is composed of Rhesus monkey erythrocyte antigens like the D antigen that can be found on the red cells of most Rh+ humans. This system is highly complicated, and some Rh alloantigens have yet to be biochemically described [8]. Because blood types are unaffected by environmental factors, they are a useful and essential resource in the pathogenesis of diseases. In this regard, many investigations have been conducted to study the relationship between cancer types, blood types, and other disorders [9].
Objectives
Also, some case series demonstrated substantial connections between blood groups and autoimmune disorders like multiple sclerosis, psoriasis, and pemphigus [10–12]. However, the exact nature of the linkage between blood groups and AA is not identified. Thus, we investigated the association between AA and ABO, and Rh systems.
Methods
The current cross-sectional study investigated the association between AA and ABO/Rh blood groups. The study was conducted on 200 cases with AA and 200 healthy controls (HCs) that attended our dermatology clinic in Hospitals between March 2021 and September 2021. Participants with other autoimmune and systemic disorders were excluded. The patients referred to the AA clinic were enrolled in the study and our healthy control objects were selected among people who did not have known systemic and skin disorders and were often referred for cosmetic problems. We matched age and sex between the two groups.
We followed the principles of the Helsinki Declaration. The Institutional Review Board of our university approved the protocol of this study. Informed consent was attained from all participants.
Statistical Analysis
SPSS version 20 (IBM Company, USA) was applied to analyze the variables. Continuous variables are displayed as mean (standard deviation), and categorical variables are reported as frequency (percentage). Student T-test (two-tailed) was applied for the comparison of continuous variables. The Chi-square or Fisher’s exact test was employed for the comparison of the categorical variables between the two study groups. A P-value <0.05 was regarded as significant.
Results
Baseline Characteristics of Participants
Two hundred patients with AA and 200 HCs were included. The baseline characteristics of the subjects in the AA and HC groups are detailed in Table 1. The two study groups were comparable in terms of age, sex, and BMI.
Table 1.
Baseline characteristics of the patients in AA and HC groups.
| AA group (n=200) | HC group (n=200) | P-value | |
|---|---|---|---|
| Age [years; mean (SD)] | 33.26 (14.33) | 33.73 (12.05) | 0.726a |
| Sex [n (%)] | 0.468b | ||
| • Male | 77 (38.5%) | 70 (35%) | |
| • Female | 123 (61.5%) | 130 (65%) | |
| BMI [kg/m 2 ; mean (SD)] | 25.87 (17.86) | 26.06 (23.11) | 0.926a |
| Disease duration [years; mean (SD)] | 8.56 (8.04) | ||
| Age of onset [years; mean (SD)] | 23.15 (12.94) | ||
| Current episode [months; mean (SD)] | 8.25 (7.71) | ||
| SALT score [mean (SD)] | 75.68 (29.93) | ||
| The pattern of hair loss | |||
| • Patchy | 81 (40.6) | ||
| • Universalis | 80 (40%) | ||
| • Totalis | 35 (17.6%) | ||
| • Ophiasis | 3 (1.6%) | ||
| Nail involvement | |||
| • None | 129 (64.6%) | ||
| • Some | 51 (25.6%) | ||
| • Dystrophy | 19 (9.6%) |
A P-value of < 0.05 was considered statistically significant.
SD: standard deviation
Student T-test
Chi-square test
Of 200 AA patients, 81 patients had patchy hair loss, 80 had Universalis hair loss, 35 had Totalis hair loss, and 3 had Ophiasis hair loss. Nail involvement was seen in 51 patients to some degree and in 19 patients as dystrophy (Table 1).
Comparison of Blood Groups Between AA Patients and HCs
Table 2 indicates the frequency of different types of blood groups in AA patients and HCs. ABO blood groups were significantly different between study groups (p=0.001). In this regard, the AA group showed a higher prevalence of the AB blood group, while the prevalence of the O, A, and B blood groups was higher in HCs (p=0.001). Nonetheless, no significant between-group differences were found based on O/non-O (p=0.391) and Rh (p=0.605) blood groups. Finally, ABO*Rh blood groups were significantly different between study groups (p=0.017). The most difference was related to the AB+ blood group, whose frequency was markedly higher in patients with AA compared to HCs (Table 2).
Table 2.
Comparison of different types of blood groups between AA and Healthy control group groups.
| AA group (n=200) | HC group (n=200) | P-value | |
|---|---|---|---|
| ABO [n (%)] | 0.001 a | ||
| • O | 60 (30%) | 68 (34%) | |
| • A | 61 (30.5%) | 79 (39.5%) | |
| • B | 21 (10.5%) | 28 (14%) | |
| • AB | 58 (29%) | 25 (12.5%) | |
| Rh [n (%)] | 0.605a | ||
| • Negative | 17 (8.5%) | 20 (10%) | |
| • Positive | 183 (91.5%) | 180 (90%) | |
| ABO*Rh [n (%)] | 0.017 b | ||
| • O− | 9 (4.5%) | 10 (5%) | |
| • A− | 3 (1.5%) | 5 (2.5%) | |
| • B− | 3 (1.5%) | 4 (3%) | |
| • AB− | 2 (1%) | 1 (0.5%) | |
| • O+ | 51 (25.5%) | 58 (29%) | |
| • A+ | 58 (29%) | 74 (37%) | |
| • B+ | 18 (9%) | 24 (12%) | |
| • AB+ | 56 (28%) | 24 (12%) |
HC: Healthy control. A P-value of < 0.05 was considered statistically significant.
Chi-square test
Fisher exact test
Association Between Blood Groups and Clinical Characteristics in Patients with AA
According to Table 3, no significant association was detected between sex, BMI, disease duration, age of onset, SALT score, patterns of hair loss, nail involvement, and ABO/Rh blood groups in patients with AA (p>0.05).
Table 3.
Association between blood groups and clinical characteristics of patients with AA.
| O | A | B | AB | P-value | Rh - | Rh + | P-value | |
|---|---|---|---|---|---|---|---|---|
| Sex [n (%)] | 0.201a | 0.201a | ||||||
| • Male | 22 (36.7%) | 30 (49.2%) | 7 (33.3%) | 18 (31%) | 9 (52.9%) | 115 (62.8%) | ||
| • Female | 38 (63.3%) | 31 (50.8%) | 14 (66.7%) | 40 (69%) | 8 (47%) | 68 (37.2%) | ||
| BMI [kg/m2; mean (SD)] | 24.37 (4.00) | 24.39 (4.62) | 30.16 (35..47) | 28.61 (35.31) | 0.687a | 25.87 (17.86) | 26.06 (23.11) | 0.926a |
| Disease duration [years; mean (SD)] | 8.90 (8.68) | 7.81 (7.55) | 7.48 (8.02) | 9.71 (7.93) | 0.290a | 8.83 (8.17) | 6.75 (6.44) | 0.310a |
| Age of onset [years; mean (SD)] | 23.81 (11.61) | 20.67 (11.30) | 19.76 (9.43) | 26.31 (16.06) | 0.175a | 23.03 (13.11) | 24.41 (11.14) | 0.667a |
| SALT score [mean (SD)] | 71.80 (31.40) | 77.44 (29.64) | 82.66 (25.92) | 75.31 (30.15) | 0.508a | 75.51 (30.71) | 77.41 (28.06) | 0.804a |
| Hair loss [n (%)] | 0.544a | 0.060a | ||||||
| • Patchy | 28 (46.7%) | 20 (33.3%) | 8 (38.1%) | 25 (43.1%) | 7 (41.2%) | 74 (40.7%) | ||
| • Universalis | 22 (36.7%) | 29 (48.3%) | 10 (47.6%) | 19 (32.8%) | 9 (52.9%) | 71 (39%) | ||
| • Totalis | 9 (15%) | 9 (15%) | 3 (14.3%) | 14 (24.1%) | 0 (0%) | 35 (19.2%) | ||
| • Ophiasis | 1 (1.7%) | 2 (3.3%) | 0 (0%) | 0 (0%) | 1 (5.9%) | 2 (1.1%) | ||
| Nail involvement [n (%)] | 0.090a | 0.457a | ||||||
| • None | 39 (66.1%) | 43 (70.5%) | 16 (76.2%) | 31 (53.4%) | 13 (76.5%) | 116 (63.7%) | ||
| • Some | 15 (25.4%) | 15 (24.6%) | 5 (23.8%) | 16 (27.6%) | 4 (23.5%) | 47 (25.8%) | ||
| • Dystrophy | 5 (8.5%) | 3 (4.9%) | 0 (0%) | 11 (19%) | 0 (0%) | 19 (10.4%) |
P-value of < 0.05 was considered statistically significant.
n Independent t-test
Discussion
We assessed the relationship between AA and ABO and Rh blood groups. The prevalence of blood groups O, A, B, and AB in patients with AA was 30%, 30.5%, 10.5%, and 29%, respectively. A significant difference was detected between the two study groups regarding the frequency of the ABO blood group. The highest difference was related to the AB blood group, so compared to HCs, patients with AA showed a higher frequency of the AB blood group. The highest difference was related to the AB+ blood group, so compared to HCs, patients with AA showed a higher frequency of the AB+ blood group.
AA is a recurrent inflammatory disorder that affects people of all ages and genders. Despite the disease’s importance, the specific etiology has yet to be fully understood. The ABO blood group family antigens have long been identified. Blood group alloantigens can be found on the membrane of epithelial cells and red blood cells. There is a link between blood types and various dermatologic conditions [9, 13, 14], leading to the elucidation of disease pathogenesis. For instance, malignant melanoma was found to have a statistically significant higher risk in patients with the O blood group [9]. Several previous reports have linked certain infections to specific ABO blood groups [15]. Tuberculoid leprosy is linked to the O blood group, while lepromatous leprosy is linked to the A and B blood groups, gonorrhea to the B blood group, smallpox to the A and B blood groups, and Escherichia coli O 157 infection to the O blood type [16]. Many studies have investigated the association between blood groups and autoimmune disorders like pemphigus Vulgaris, DM, RA, spondyloarthropathy, vasculitis, Behcet’s disease, SLE, systemic sclerosis, and Sjogren’s syndrome [10,17, 18]. Among these, no link was found between the ABO blood types and pemphigus Vulgaris, which is a well-known autoimmune skin disorder [18, 19]. In the etiopathogenesis of AA, autoimmunity is more prominent. Different researchers have established the relevance of T cells in the disease [20]. However, genetic variables play a role in illness susceptibility and severity as well. In single-twin investigations, the frequency of concurrent disease was found to be 55 percent, indicating that genetic and environmental variables play a role in the disease’s development [20, 21]. The genes that code for blood group antigens are found on chromosome 9q34.2 (for the ABO blood group) and chromosome 1p36.11 (for the Rh blood group) [22].
Up to now, only two investigations have examined the relationship between blood type and AA. In 2018, İslamoğlu et al. [23] conducted a clinical study in Turkey to investigate the association between alopecia areata and ABO and Rh blood groups. They indicated a similar distribution of the ABO blood group in the patient and healthy groups. However, the Rh+ blood group was markedly higher in the healthy group than the patient group. Also, Rather et al. [24] conducted a case-control study in Kashmir to examine the relationship between ABO blood groups and different skin diseases (psoriasis, vitiligo, AA, pemphigus Vulgaris). Also, 37.1% of patients with psoriasis showed O blood group, followed by type B (30%) and A (25.7%), with no significant differences between study groups. In cases with vitiligo, 47.4% showed the B blood group, followed by blood groups O (36.8%) and A (10.5%). The frequency of A and B blood groups was significantly different between vitiligo patients and controls. In AA patients, blood group B was detected in 45.2% of patients, and groups O (28.6%) and A (19%) ranked second and third, with no significant differences between study groups. In patients with pemphigus Vulgaris, 40% of patients showed O and B blood groups, followed by blood group A (20%), with no significant differences between the groups. Contrary to the results of these studies, a significant difference was found between the two groups in our study. The highest difference was related to the AB+ blood group, so compared to the control group, patients with AA belonged to the AB blood group with higher frequency. We also examined the relationship between the characteristics of AA and the frequency of ABO and Rh blood groups; no significant association was detected between ABO or Rh blood groups and sex, BMI, disease duration, age of onset, SALT score, hair loss pattern, and nail involvement in patients with AA.
Conclusion
A significant difference was found between the two groups regarding the frequency of the ABO*Rh blood group. The frequency of the AB+ blood group was higher in patients with AA. Further studies could verify the results of this study.
Footnotes
Funding: It is financially supported by the vice-chancellor of research affairs of the Tehran University of Medical Sciences.
Competing Interests: None.
Authorship: All authors have contributed significantly to this publication
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