Vitiligo

The clinical image provided shows multiple, well-demarcated, milky-white patches on the dorsum of the hand and fingers. What is the most likely diagnosis?

A 28-year-old man from Mumbai presents with depigmented patches on his left hand and left side of his face that appeared 6 months ago following a minor cut on his hand. The patches are well-demarcated, non-scaly, and have progressed rapidly over the first 3 months but have remained stable for the past 3 months. He reports no family history of similar lesions. Examination reveals unilateral depigmentation following a dermatomal distribution. Thyroid function tests and autoimmune screening are negative. What is the most likely diagnosis and what is the expected clinical course?

A 32-year-old woman from Delhi presents with a 2-year history of progressive depigmented patches on her hands, face, and neck. The patches are well-demarcated, non-scaly, and non-pruritic. She reports that her maternal grandmother had similar lesions. On examination, the affected areas show complete loss of pigmentation with sharp borders. Wood's lamp examination reveals enhanced visualization of the depigmented areas. Histopathology shows complete absence of melanocytes. She is otherwise healthy with normal thyroid function and negative autoimmune serology. What is the most likely diagnosis?

A 32-year-old woman from Delhi presents with a 2-year history of progressive depigmented patches on her face, neck, and dorsal hands. The patches are well-demarcated, non-scaly, and asymptomatic. She reports that her maternal grandmother had a similar condition. On examination, the depigmented areas show complete loss of pigmentation with sharp borders. Wood's lamp examination reveals enhanced demarcation of the lesions. She denies any history of trauma or chemical exposure. Laboratory investigations show normal thyroid function and negative tissue transglutaminase (tTG) antibodies. What is the most likely diagnosis?

A 24-year-old woman presents with a 6-month history of progressive loss of skin pigmentation. Examination reveals well-demarcated milky-white macules and patches distributed symmetrically over the face (perioral and periorbital regions), hands, and elbows. The lesions are asymptomatic. Under Wood lamp examination (365 nm), the affected areas show bright blue-white fluorescence. The structure marked **A** in the diagram represents the characteristic appearance of these lesions. Which of the following best describes the PRIMARY PATHOGENIC MECHANISM underlying the development of the lesions marked **A**?