<prompt> The commonest focus of scrofuloderma isLungLymph nodesLarynxSkin  <response>: Scrofuloderma is a skin condition caused by tuberculosis involvement of the skin by direct extension, usually from underlying tuberculous lymphadenitis. Ref: Textbook of microbiology; Ananthanarayan and panikers; 10th edition; Pg: 367 