**3.7 Vitamin D deficiency and systemic sclerosis**

Systemic sclerosis is a chronic, inflammatory, fibrotic disorder thought to be related to autoimmune etiology. Vitamin D deficiency has been observed in patients with systemic sclerosis [86, 131], especially in patients with the diffuse type of the disease [131].

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*Vitamin D and Autoimmune Diseases*

**4. Optimal levels of 25(OH)D3**

**5. Conclusions**

**Conflict of interest**

The authors declare no conflict of interest.

*DOI: http://dx.doi.org/10.5772/intechopen.89707*

25(OH)D3 level of at least 32 ng/ml appears sufficient.

The molecule used to assess vitamin D sufficiency in a population is 25(OH)D3 [9]. It appears that vitamin D has physiologic effects beyond those related to bone physiology and mineral homeostasis. It may be that the alarming prevalence of vitamin D deficiency observed all over the globe may be contributing to the development of autoimmune diseases. Based on bone-related biomarkers such as intact parathyroid hormone, calcium absorption, and bone mineral density, maintaining a

It appears that vitamin D is a potent immunomodulator. It has multiple and diverse effects on the immune system. In particular, it potentiates the innate immune response enhancing the production of cathelicidin from human macrophages, monocytes, and keratinocytes, thus enhancing and potentiating the immune response against external pathogens. It affects the adaptive immune response shifting the phenotype of the adaptive immune response toward a more tolerogenic phenotype. Vitamin D deficiency is related to various autoimmune disorders. Vitamin D deficiency appears to be related to the development of RA and correlates with disease severity. Vitamin D deficiency is observed in patients with SLE. It was found to be related to disease severity and activity in some but not all studies. Vitamin D deficiency is observed in patients with multiple sclerosis, and vitamin D administration may ameliorate disease severity. Vitamin D deficiency is also observed in patients with inflammatory bowel disease, Crohn's disease, and ulcerative colitis, and it is related to disease activity. Vitamin D contributes to the integrity of the intestinal barrier and bacterial homeostasis. In addition, vitamin D absorption is decreased making supplementation important. Vitamin D deficiency is also observed in patients with autoimmune Hashimoto's thyroiditis. Vitamin D deficiency is found in patients with systemic sclerosis, especially the diffuse form of the disease. It appears that optimal levels of vitamin D are important for immune

function and for the prevention of autoimmunity in the human organism.
