Differential Diagnosis for a 58-year-old man with a history of schizophrenia and ongoing methamphetamine abuse presenting with white painful lesions on the side of his tongue

• Single most likely diagnosis
  • Methamphetamine-induced oral lesions: The patient's ongoing methamphetamine abuse is a significant risk factor for oral lesions, which can be painful and appear white due to tissue damage and potential secondary infection.
• Other Likely diagnoses
  • Oral candidiasis (thrush): Immunocompromised states, poor oral hygiene, and drug abuse can predispose individuals to fungal infections like candidiasis, which presents with white lesions on the mucous membranes.
  • Leukoplakia: This condition, characterized by white patches on the mucous membranes, can be associated with chronic irritation, such as from tobacco or methamphetamine use, and has a potential for malignant transformation.
  • Lichen planus: An autoimmune condition that can affect the mucous membranes, including the tongue, causing white, lacy patches and painful lesions, potentially exacerbated by stress or drug use.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Oral cancer: Although less likely, the presence of a painful lesion, especially in a patient with a history of substance abuse, necessitates consideration of oral cancer, as early detection significantly improves prognosis.
  • Syphilitic gumma: In the context of methamphetamine abuse, which may increase risky sexual behavior, syphilis should be considered, as it can cause oral lesions in its tertiary stage.
• Rare diagnoses
  • Pemphigus vulgaris: An autoimmune disease causing blistering of the skin and mucous membranes, which can present with painful lesions, though it is less common and would require specific diagnostic testing.
  • Histoplasmosis: A fungal infection that can cause oral lesions, particularly in immunocompromised individuals, though it is less likely without specific exposure history or systemic symptoms.