Palmar Lesions and Moth-Eaten Alopecia in a 23-Year-Old Man

A man with suspected but untreated secondary syphilis had nonscarring alopecia, photodistributed facial eruption, oral ulcers, leukopenia, and low C3 level; biopsy of a palmar lesion showed dyskeratotic keratinocytes, basal vacuolar alteration, papillary dermal edema, and perivascular and periappendageal infiltrates of lymphocytes and histiocytes. What is the diagnosis and what would you do next?