Homocysteine is a sulfur containing amino acid that is generated during the conversion of methionine to cysteine. The normal ranges of homocysteine is from 5 to 15μmol/L. Multiple cofactors and enzymes are needed for the metabolic pathways of homocysteine such as vitamin B12, B6, folate, 5,10-methylenetetrahydrofolate reductase enzyme, cystathionine -β- synthase enzyme. Thus deficiency of these cofactors due to genetic or acquired factors may cause hyperhomocysteinaemia which is mild to moderate elevation of homocysteine in the blood or serum. Hyperhomocysteinaemia was recently found to be related to different dermatologic diseases such as: Psoriasis, vitiligo, Behcet’s disease, systemic lupus erythematosus, scleroderma, Raynaud’s disease, livedoid vasculopathy, purpura, wounds and squamous cell carcinoma. The aim of the study is to elaborate the role of homocysteine in different dermatologic diseases.