A 28-year-old woman presents with progressive milky-white patches on her hands and face over the past 6 months. On examination, the structure marked **A** shows well-demarcated depigmented macules with sharp borders against normal skin. Wood's lamp examination accentuates the lesions as bright blue-white fluorescence. She has a family history of thyroid disease. Based on the clinical presentation and the pathophysiology of the condition affecting the structure marked **A**, which of the following is the MOST appropriate initial screening investigation?
A. Intradermal tuberculin test
B. Fasting blood glucose and HbA1c
C. Serum cortisol and ACTH levels
D. Serum TSH and anti-TPO antibodies
Explanation
Why Serum TSH and anti-TPO antibodies is right
The structure marked A — well-demarcated depigmented macules and patches — is the hallmark of vitiligo, an acquired chronic autoimmune depigmenting disorder caused by progressive loss of functional melanocytes from the epidermis. Vitiligo is strongly associated with other autoimmune disorders, particularly autoimmune thyroid disease (Hashimoto thyroiditis and Graves disease), which is present in 15–20% of vitiligo patients. Given this patient's family history of thyroid disease and the confirmed diagnosis of vitiligo, screening for thyroid dysfunction with TSH and anti-TPO antibodies is the most appropriate initial investigation per IADVL and VGICC guidelines. Annual thyroid screening is recommended in all vitiligo patients.
Why each distractor is wrong
Fasting blood glucose and HbA1c: While type 1 diabetes mellitus is associated with vitiligo, it is less common than autoimmune thyroid disease and does not have the same prevalence or screening urgency. This would be a secondary screening test if thyroid disease is ruled out.
Intradermal tuberculin test: Leprosy is an important differential diagnosis of vitiligo in the Indian context (due to hypopigmented patches with anesthesia and nerve thickening), but tuberculosis screening is not indicated by vitiligo itself. Leprosy is ruled out clinically by the absence of sensory loss and nerve thickening.
Serum cortisol and ACTH levels: Addison disease is a rare association with vitiligo and is not part of routine screening. It would be investigated only if clinical signs of adrenal insufficiency (hypotension, hyperpigmentation, electrolyte abnormalities) are present.
High-YieldNEET PG
Vitiligo is an autoimmune disorder; screen for associated autoimmune thyroid disease (15–20% prevalence) with TSH and anti-TPO antibodies annually — this is the highest-yield screening test in all vitiligo patients, especially those with family history.
Rook's Textbook of Dermatology 10e; VGICC Consensus; IADVL Vitiligo Guidelines
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