Oral Thrush (Candidiasis): This is a common condition, especially in immunocompromised individuals, characterized by white spots on the tongue and mucous membranes due to a fungal infection. It's often associated with antibiotic use, poor oral hygiene, or immunosuppression.

Leukoplakia: A condition where thick, white patches or lesions appear on the tongue, often related to chronic irritation or tobacco use. It can sometimes be a precursor to oral cancer.
Lichen Planus: An autoimmune condition that can affect the mucous membranes inside the mouth, leading to white, lacy patches on the tongue and other areas.
Geographic Tongue: A benign condition characterized by the appearance of single or multiple, well-demarcated areas of depapillation on the tongue surface, giving it a "geographic" appearance.

Oral Cancer: Although less common, any unusual or persistent lesions on the tongue should raise suspicion for oral cancer, especially in individuals with risk factors like tobacco or alcohol use.
Syphilis (Secondary): In its secondary stage, syphilis can cause a variety of oral manifestations, including mucous patches on the tongue, which are highly infectious.
Aphthous Ulcers: While typically appearing on the inside of the cheeks or lips, aphthous ulcers can occasionally occur on the tongue and should be considered, especially if the patient reports pain.

Pemphigus Vulgaris: A rare autoimmune disease that can cause blistering of the skin and mucous membranes, including the tongue.
Erythema Multiforme: A skin condition that can also affect the mucous membranes, leading to lesions on the tongue, often in response to an infection or medication.
Histoplasmosis: A fungal infection that can cause oral lesions, including on the tongue, particularly in immunocompromised individuals.