A patient presented with scarring alopecia, thinned nails, hypopigmented macular lesions over the trunk and oral mucosa. The diagnosis is –
Most of the guide have given lichen planus as the answer.
But, None of the given option is fully correct.
Patient in this question is presenting with -


Scarring alopecia
Thinned nails
Hypopigmented macular lesions
Involvement of oral mucosa


Psoriasis and pemphigus are out of question as these two don't cause alopecia.
Two options left are leprosy and lichen planus, both can cause scarring alopecia

i). Thinned nail and oral mucosal involvement favour lichen planus as diagnosis, but the lesion of Lichen planus is hyperpigmented, i.e. hyperpigmented violoceous plaques and surrounding hyperpigmented macules.
ii)   Hypopigmented macule can occur in leprosy, but nail thinning rule out leprosy.

So, No options is absolutely correct.
If we consider that there was misprinting in the question (i.e. hypopigmentation instead of hyperpigmentation), than you can go ahead with lichen planus.
Psoriasis
Leprosy
Lichen planus
None