Angular Cheilitis: This condition is characterized by inflammation of the corners of the mouth, often leading to skin cracking. It is commonly associated with vitamin deficiencies (e.g., vitamin B12, iron), fungal infections (like candidiasis), or bacterial infections. The cracking at the lip folds is a hallmark symptom, making it the most likely diagnosis.

Eczematous Cheilitis: A form of eczema that affects the lips, causing dryness, cracking, and inflammation. It can be due to allergic reactions, irritants, or atopic dermatitis.
Actinic Cheilitis: A condition caused by prolonged exposure to sunlight, leading to dry, cracked lips, and potentially increasing the risk of lip cancer.
Contact Dermatitis: An allergic or irritant reaction to substances like cosmetics, toothpaste, or food, which can cause lip cracking among other symptoms.

Lip Cancer: Although less common, skin cracking at the lip folds could be an early sign of lip cancer, especially in individuals with a history of tobacco use or excessive sun exposure. Early detection is crucial for effective treatment.
Syphilis: Secondary syphilis can cause mucocutaneous lesions, including cracking at the corners of the mouth. Given the potential for serious complications if left untreated, syphilis should not be overlooked.

Sjögren's Syndrome: An autoimmune disorder that can cause dryness in the mucous membranes, including the lips, potentially leading to cracking.
Graft-Versus-Host Disease (GVHD): In individuals who have undergone bone marrow or stem cell transplants, GVHD can cause a variety of skin symptoms, including dryness and cracking of the lips.
Pemphigus: A group of rare skin disorders that cause blistering of the skin and mucous membranes, which can lead to cracking and erosion of the lip folds.