A child presents with solitary white well defined patch on his right thigh. Diagnosis is - (AIIMS Nov 2013)
a. Information is this question are :-
i) Lesion is on thigh
ii) Unilateral lesion (Isolated lesion on Right thigh)
b. Both these suggest Nevus achromicus, i.e. Nevus acromicus involves :-
i) Trunk and proximal extremity (thigh in this question)
ii) Lesion is unilateral
c. Also keep in mind that, though Nevus achromicus presents since birth, it may be missed at birth and the patient may present in childhood (as in this question).
About other options
a. Piebaldism involves extremity bilaterally symmetrical and there is characteristic white forelock which cannot be missed at birth.
b. In albinism there is diffuse hypopigmentation of skin and hair throughout the body which cannot be missed at birth.
c. Acral vitiligo, as the name suggests involves acral areas (finger, toes, palms and soles).