Psoriasis is a chronic inflammatory and proliferative skin condition that results from complex interaction of the innate and acquired immunologic system and is characterized clinically by sharply defined erythematous plaques with silvery white scales predominantly on extensor surfaces and scalp with chronic and relapsing course. [1]. The presence of vitamin D receptor in keratinocytes was first established from in vitro study of cultured keratinocytes in 1988 and afterward many in vitro and clinical studies have well-documented the role of vitamin D in proliferation and differentiation of keratinocytes [2]. Its aetiology is unknown; involving various environmental, genetic and immunological factors. On the basis of HLA-Cw6 association it is divided into type 1 psoriasis which is early onset HLA associated and type 2 psoriasis which is late onset HLA not associated. According to genome wide association studies there are mainly 9 psoriasis susceptible genes (PSORS 1-9) known which accounts for psoriasis risk. It involves both type of immune system with classical involvement of Th1, Th17, and Th22 pathway. The prevalence varies from 0.44% - 2.8% in India; 1 with equal sex ratio and bimodal age of onset.

Vitamin D inhibits keratinocytes’ proliferation and induces their differentiation. Thus, these two important findings of vitamin D in keratinocytes have led to the discovery of the role of vitamin D in the pathogenesis of psoriasis, i.e., a decrease in vitamin D causes an increase in proliferation of keratinocytes and cutaneous inflammation [3].Upon damage to keratinocyte due to any cause in psoriasis susceptible individual there is increased production of antimicrobial peptide (LL-37) and various cytokines mainly TNF alpha, INF gamma, IL 6, IL 1beta, IL 12, IL 23 via activated dendritic cell resulting in T cell differentiation, keratinocyte hyper-proliferation and neutrophil and lymphocyte infiltration forming a psoriatic plaque. There is a cross-talk between epidermal and dermal cells with release of various growth factors and chemokine forming a self-perpetuating inflammatory loop. Psoriasis is classified into many types, most common being chronic plaque psoriasis also known as psoriasis vulgaris.

Vitamin D has several important functions and has a significant place in human health. A number of studies showed a high occurrence of Vitamin D deficiency among aged males and females, immature adults, and children. Levels of Vitamin D in the serum are consistently changing, after summer it reaches at maximum while after winter it reaches its minimum [4-14]. Vitamin D is believed to be synthesized from exposure to sun. Whereas UVB exposure helps keratinocytes in the epidermis to synthesize pre Vitamin D3, later converted to active Vitamin D known as 1,25 dihydroxyvitamin D3. Vitamin D has many biological functions such as multiplication and differentiation of keratinocytes, maintaining the cycle of hair follicles, and suppressing tumors. Studies have established that Vitamin D also exhibits photo protective, anti-inflammatory and wound healing effects [15-20].

A cross sectional study of 110 cases of psoriasis was included from February 2022 to January 2023 after getting the approval from the institutional ethical committee and consent from the patient. Serum levels of calcium,    phosphorus,    parathyroid    hormone    (PTH),    alkaline phosphatase  (ALK)  and  25-  hydroxyl  vitamin  D3  [(25OH)  D3]  were measured  in  both  groups.

STUDY DESIGN AND PARTICIPANTS

A cross-sectional survey was done targeting psoriatic patient with prior approval from the ethics committee of the institute.

SAMPLES OF THE STUDY- A total of 110 patients were included in the study.

STUDY DURATION: 12 months duration from February 2022 to January 2023.

Inclusion criteria:

Clinically diagnosed psoriasis patients and healthy controls of age > 15 years of any sex.

Exclusion criteria:

Other types of psoriasis patient and those on treatment, which might influence vitamin D status.

Fig:1- Psoriasis on arms                                     Fig:2- Plaque Psoriasis

Fig: 3-Psoriasis: A reddish, scaly rashlocated over the surfaces of the knees and elbows

STATISTICAL ANALYSIS:

The data collected were tabulated and analyzed by SPSS, version 17.0. Qualitative data were described using number and percent. The Kolmogorov–Smirnov test was used to verify the normality of distribution. Quantitative data were described using range (minimum and maximum), mean, SD, and median.

Among110 patients with psoriasis 63 (57.27%) were men and 47 (42.72%) were women. There was no significant difference in the serum level of calcium (P-value: 0.552), phosphorus (P-value: 0.372), PTH (P-value: 0.353) and ALK (P-value: 0.648) between two groups. Vitamin D deficiency was found in 63.4 % of psoriatic patients and 58% of the controls (P-value=0.45); However 31.8% of psoriatic and 16.2% of the controls suffered from severe hypovitaminosis D. This difference was statistically significant (P-value=0.013)                       

Psoriasis is a hyper-proliferative disorder of the skin, and vitamin D3 analogs are widely used in its treatment [11, 21]. Among special properties of 1,25(OH)2D3 are both a pro-differentiating and an antiproliferative influence on normal and cancer cells, as well as some immunomodulatory effects [22]. The aim of this study is to investigate serum levels of vitamin D in patients with psoriasis compared with healthy controls, and to consider their relation to disease severity. For this purpose, 110 patients with psoriasis of different variety and age‑matched and sex‑matched healthy controls were included in this study. The patients of this study were divided into four groups: group -I (included age‑matched and sex‑matched healthy controls); group -II (included chronic plaque psoriasis patients with mild activity with PASI score 20.

In the current study, there was no significant difference between patients and controls regarding age and sex. This went with Orgaz‑Molina et al. [23]. In the current study, there was no significant statistical difference between patients and controls regarding family history and sun exposure.This went with Maleki et  al.  [24]. Allayali et  al. [25] who showed that 14% of all participants of the study had a positive family history of psoriasis, while only 11  (16.2%) psoriatic patients had a positive family history of psoriasis with no significant difference between cases and control. Feldmeyer et  al. [26] observed that phototherapy with UVBnb and UVA/UVBnb increased the 25‑hydroxycholecalciferol serum level significantly, whereas UVA1 therapy alone induced a reduction in serum 25‑hydroxycholecalciferol concentration. However, a considerable source of vitamin D that enables the limitation of sun exposure seems to be its additional food intake in the form of certain foods or dietary supplements. Most meals contain only a little vitamin D3 and those rich in vitamin D3 are eaten irregularly [27]. In the current study, there was significant decrease in the level of serum vitamin D in moderate and severe patient groups compared with the control group whereas non-significant difference existed between mild cases and control. There is also significant decrease in the level of serum vitamin D in severe cases compared with moderate cases, whereas nonsignificant difference existed between mild and moderate patient groups. This agrees with Abdalla and Abdrabo [28]. The results of Filoni et al. [29] confirmed the reduced vitamin D level in psoriatic patients when compared with healthy controls. These provide new evidence regarding the association of vitamin D level and psoriasis. It was reported that deficiency of vitamin D has been implicated as an environmental trigger for immune‑mediated disorders including psoriasis and PA  [30]. It was documented that vitamin D status has been associated with an increased risk for Th1 cytokine‑mediated autoimmune diseases including insulin-dependent diabetes mellitus (IDDM), multiple sclerosis (MS), inflammatory bowel disease, and rheumatoid arthritis (RA) [31]. The present study detected lower levels of circulating vitamin D in patients with severe psoriasis than in mild and moderate cases. This finding can be explained by the liposolubility of vitamin D and its reduced bioavailability in bodies with a high fat content. Obesity is associated with basic systemic inflammation, characterized by an increase in proinflammatory markers such as TNF‑α and IL‑6 [32]. The current study showed that there was significant negative correlation between serum vitamin D levels and each of age, duration of disease, and PASI score. Non-significant positive correlation existed with age of onset. This agrees with the results of Bergler‑Czop and Brzezińska‑Wcisło [33]. In the current study cause–effect relationship could not be determined whereas Schwalfenberg [34] reported that low levels of vitamin D may have important implication in the pathogenesis of psoriasis. Vitamin D regulates keratinocyte growth and differentiation. Topical vitamin D derivatives are extensively used as monotherapy or in combination with steroids for the topical treatment of psoriasis. The current study showed that vitamin D was an independent factor of psoriasis to differentiate between patients and controls. At a cutoff value of less than or equal to 39.23 ng/ml, the sensitivity was 93.33, specificity 80.0%, PPV 93.3%, and NPV was 80.0%. The current study found that PASI score and vitamin D serum level were independent factors to predict cases from controls, mild cases from moderate and severe cases, and severe cases from mild and moderate cases. PASI score has higher sensitivity, specificity, PPV, and NPV. It was found that treatment with vitamin D (35.000 IU daily) resulted in a significant increase in serum level of 25‑hydroxycholicalciferol, which correlated with a significant improvement in the PASI score of all patients [35]. It was documented that patients with psoriasis may have lower vitamin D level than the ordinary population due to a series of factors. Low 25(OH)D level can either represent the cause or consequence of psoriasis, resulting from lack of sun exposure from frequent use of drugs that interfere with 25(OH)D metabolism such as gluco‑corticoids and immune-suppressive agents or from low 25(OH)D intake [36]. Many studies have shown the association between serum level of vitamin D and psoriasis [37]. Other studies have shown no association between serum level of vitamin D and psoriasis [38].

The study found a significant relationship between vitamin D and psoriasis. Vitamin D levels benefits patient with psoriasis vulgaris.This finding revealed the need for evaluation of psoriatic   patients   for   the   presence of   vitamin   D deficiency. Further metaanalysis involving larger study population will be required to establish whether vitamin D levels benefits patient with psoriasis vulgaris.

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