Dr. Callen presents cases that represent a myriad of cutaneous manifestations of systemic diseases.
He is the author or co-author of 69 original articles, 122 case reports, 117 review articles, 18 editorials, 10 books, 110 book chapters, and 88 abstracts. He served as an Assistant editor of the Journal of the American Academy of Dermatology (1993-2003), and is a member of the editorial boards of the Journal of Rheumatology, Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontics, eMedicine, Best Practice of Medicine, Journal of Cutaneous Medicine and Surgery, Journal Watch Dermatology, and the Journal of the European Academy of Dermatology and Venereology. He has been the editor in Chief of Advances in Dermatology (1986-1996) and the Editor in Chief of Current Problems in Dermatology (1996-2003). He is the current Associate Editor of the Archives of Dermatology.