Lichen planus (LP) is a chronic inflammatory disease which affects skin, mucous membranes, scalp and nails with a prevalence of 0.5-2% in general population. Cutaneous LP is characterized by purple, polygonal, flat topped, pruritic papules and plaques. The sites that are commonly affected are flexor surfaces of forearms, wrists, ankles and also the trunk.1 The exact cause of LP is unknown, it is attributed to a number of triggers such as drugs, contact allergens, genetic and immune mechanisms. The immune mechanism targets basal keratinocytes and it is mediated by CD8+, CXCR3+ cytotoxic t cells. There is Th-1 mediated releases of inflammatory cytokines such as interferon-gamma, from the cytotoxic T-cells. Interferon-gamma activity is associated with an increase in the expression of CXCL10, CXCL9 AND CXCL11, at the papillary dermis and dermo epidermal junction.

Histological features of LP are band like lymphocytic infiltrate at the papillary dermis close to the epidermis, vacuolar degeneration of basal keratinocytes and presence of civatte bodies. Corticosteroids form the main stay of therapy for LP2. Localised LP can be treated with high potency topical corticosteroids.  Generalised LP requires treatment with systemic corticosteroids, commonly prednisolone for unresponsive cases, acitretin and UVB phototherapy are used as second line therapy3. Systemic corticosteroids cannot be used for prolonged periods due to their adverse effects such as weight gain, hyperlipidaemia, hyper glycemia, peptic ulcer disease, oesophageal reflux, bowel perforation, Cushing’s disease, Addisonian crisis, cataract and glaucoma4.

A novel approach has been proposed to minimize the side effects of daily dosing regimens in which a single dose of long-acting steroid such as betamethasone is administered 2 days a week. This weekly dosing pulse regimen of low dose steroid is known as oral mini-pulse therapy. Oral mini pulse increases compliance and can be preferred over the standard regimens in patients who are more prone to adverse effects of systemic corticosteroids. Betamethasone 5mg or 6mg once or twice a week is being used routinely5.

Methotrexate [MTX] is an anti- metabolite which is approved for use in malignancies, rheumatoid arthritis, Psoriatic arthritis. In dermatology it is being used for Psoriasis, Sezary syndrome, Immuno-bullous disorders, proliferative disorders, autoimmune connective tissue diseases and vasculitis. Methotrexate is a competitive inhibitor of the enzyme dihydrofolate reductase, which is essential for the synthesis of nucleotides of DNA. As a result, immunosuppression is achieved by inhibition of DNA synthesis in immunologically competent cells. MTX also exerts antiproliferative effect on T-cells. MTX mediated increase in adenosine production reduces inflammation.4

MTX supresses both B and T cell immune responses,4 as a result it is efficacious in LP where there is T-cell mediated destruction of keratinocytes. MTX suppresses the chemotaxis of inflammatory cells6 by virtue of which the chemokines released in LP are supressed. MTX can be used as a safe alternative in cases of LP which are difficult to treat.