Table 2. Studies reporting the role of cytokines and homocysteine.

HTN: hypertension; ROS: reactive oxygen species; HOMA-IR: homeostatic model assessment of insulin resistance; LDL: low-density lipoprotein; HDL: high-density lipoprotein; SBP: systolic blood pressure; NE: nor-epinephrine; E: epinephrine; NMN: nor-metanephrine; MN: metanephrine; HVA: homovanillic acid; 5-HIAA: 5-hydroxyindoleacetic acid

Author	Year	Type of study	No. of patients	Purpose of study	Result	Conclusion
Namazi et al. [2]	2020	Case-control	83	To investigate the relationship between hypertension and vitiligo	Increased prevalence of HTN in vitiligo	Increased prevalence of HTN in vitiligo due to increased stress-causing release of catecholamines
Mitra et al. [17]	2017	Cross-sectional	51	To investigate the relationship between ROS and cytokines in patients with vitiligo	Generation of ROS was higher in patients with vitiligo along with increased levels of pro-inflammatory cytokines	Enhanced production of ROS-mediated lipid peroxidation, DNA damage, along with a decline in antioxidant capacity was accountable for disease progression
Karadag et al. [18]	2011	Case-control	57	To investigate the relationship between vitiligo and insulin resistance	Patients with vitiligo had elevated HOMA-IR, insulin, and C-peptide levels, increased LDL-to-HDL ratio, and reduced HDL  cholesterol with an increase in mean SBP	Increased insulin resistance in vitiligo could be connected to mechanisms other than obesity like cytokine production or autoimmune reaction to melanocytes
Pietrzak et al. [19]	2014	Case-control	34	To assess lipid profile in vitiligo-affected children	Increased LDL, decreased HDL, and increased LDL/HDL and TG	Lipid disturbances in vitiligo patients were probably due to metabolic disturbances in adipose tissue and oxidative stress
Cucchi et al. [20]	2000	Case-control	70	To investigate the association between vitiligo and monoaminergic system	Levels of NE, E, NMN, MN, HVA, 5-HIAA were remarkably elevated in patients with vitiligo	Higher levels of catecholamines and metabolites indicate increased activity of the monoaminergic system, which might be due to stressful events
Orecchia et al. [21]	1994	Case-control	40	To investigate the relationship between vitiligo and monoaminergic system	HVA and NMN levels were increased. Both catecholamines and metabolites showed higher concentration in patients with a shorter duration of disease but were statistically not significant	Monoaminergic systems were unlikely to be related to vitiligo
Taneja et al. [22]	2020	Cross-sectional	54	To investigate homocysteine levels and lipid risk factors in vitiligo	Increased levels of LDL, homocysteine and LDL/HDL. Decreased level of HDL	Increased homocysteine levels may be a precipitating factor in the pathogenesis of vitiligo. Increased lipid levels may be due to abnormal metabolic processes
Tsai et al. [23]	2019	Review article	1,215	To investigate the role of homocysteine, folate, and vitamin B12 levels in vitiligo	Increased level of homocysteine, decreased level of B12, and folate levels not significantly raised	Vitiligo was associated with higher homocysteine and lower vitamin B12 levels, which correlate with disease activity
Singh et al. [24]	2011	Case control	30	To investigate the association between homocysteine levels and vitiligo	Increased homocysteine levels in patients with vitiligo	Increased homocysteine levels may be the cause for vitiligo in predisposed individuals