Lichen planus: An inflammatory condition of the skin and mucous membranes.

Lymphoma: A cancer of the lymphatic system.

Pityriasis rubra pilaris: The name given to a group of rare skin disorders that present with reddish-orange colored scaly patches with well-defined borders. They may cover the entire body or just parts of the body such as the elbows and knees, palms and soles.

Psoriasis: A condition in which skin cells build up and form scales and itchy, dry patches.

Sebaceous glands: These glands are present in the dermis of the skin and secrete an oily or waxy substance called sebum that lubricates the skin and hair shafts and makes them waterproof.

Seborrheic dermatitis: A skin condition that causes scaly patches, red skin and inflammation mainly on the scalp.

Sweat glands: These glands are present in the dermis of the skin and secrete a dilute watery fluid called sweat, which helps in excretion and temperature regulation by evaporating from the skin surface.

Vitamin D: Also known as the “sunshine vitamin”, it is synthesized primarily in the epidermis of the skin upon exposure to sunlight.