Pityriasis Versicolor: A common fungal infection caused by Malassezia yeast, characterized by patches of discoloration, typically on the back, chest, and shoulders. The patches can be lighter or darker than the surrounding skin and are often accompanied by a fine scale.

Vitiligo: An autoimmune condition leading to the loss of pigment-producing cells (melanocytes), resulting in white patches on the skin. It can appear anywhere on the body, including the back.
Tinea Corporis (Ringworm): A fungal infection that can cause circular patches of rash on the skin, including the back. These patches are often clear in the center and can have a raised, red border.
Seborrheic Dermatitis: A skin condition causing scaly patches, red skin, and stubborn dandruff. It often affects oily areas of the body, such as the back.

Leprosy (Hansen's Disease): A chronic bacterial infection that primarily affects the skin, nerves, and mucous membranes. It can cause light-colored patches on the skin, among other symptoms. Although rare in many parts of the world, missing this diagnosis can lead to significant morbidity.
Sarcoidosis: An inflammatory disease that can affect multiple parts of the body, including the skin, lungs, and eyes. Skin symptoms can include rashes and lesions, which might appear as white patches.

Idiopathic Guttate Hypomelanosis: A condition characterized by small, discrete, hypopigmented macules, typically on the extremities but can appear on the back. The cause is unknown, and it's more common in older adults.
Piebaldism: A rare genetic disorder of melanocyte development, characterized by the absence of melanocytes in affected areas of skin and hair, leading to white patches and often hair loss in these areas. It's present at birth.