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Our Practice

We provide the best dermatologic care, employing the latest scientific and pharmacologic technologies.

The San Luis Dermatology and Laser Clinic has been serving the San Luis Obispo area in the person of Dr. Jeffrey Herten since October 1977. From one doctor, one nurse, and one front office person practicing in an 800-square-foot office, the clinic has grown into four physicians with a physician assistant and twenty support staff now practicing in three locations in San Luis Obispo County.

The clinic offers the latest in diagnostic and therapeutic clinical dermatology, expert cancer diagnosis and surgery including Mohs Micrographic Surgery, dermatoscopic evaluation, and digital photography on atypical moles leading to the early diagnosis and treatment of melanoma. All these technologically advanced services are provided by caring healthcare professionals assisted by friendly and efficient nurses, medical assistants, and support staff.

R. Jeffrey Herten, M.D. FAAD (Retired from practice on 1/31/24)

Diplomate of the American Boards of Dermatology and Dermatopathology. Dr. Jeffrey Herten has 45 years of experience in the practice of Dermatology, Dermatologic Surgery, Mohs Micrographic Surgery, and Dermatopathology.

Michael P. Heffernan, M.D., FAAD ​

Dr. Heffernan grew up in a small town coastal New Hampshire. He was the first person in his family to attend college. He received his undergraduate degree from the University of Notre Dame, his medical degree from the University of Michigan, and trained in Dermatology at Stanford where he was chosen to be chief resident.

Dr. Heffernan then served our country in the Air Force. After returning from service, he taught at Washington University and Wright State University where he also served as Chairman of the Department of Dermatology and Residency Program Director. Dr. Heffernan’s research has led to the development of dozens of medications. He recently served as a Distinguished Medical Fellow and Senior Medical Director at Eli Lilly & Co.

Dr. Heffernan is an internationally recognized dermatologist for problems ranging from the common to the complex. He specializes in the management of skin cancer and pre-skin cancers. He also specializes in the management of all complicated dermatologic disorders including psoriasis, lichen planus, mycosis fungoides, vasculitis, and pemphigus.

Dr. Heffernan is blessed with a great wife and 4 rambunctious daughters who are looking forward to establishing deep roots in San Luis Obispo.

Charles B. Fishman, M.D.

Dr. Fishman graduated from Indiana University School of Medicine in 1968. He interned and took one extra year of Internal Medicine residency at Wadsworth-VA-UCLA Hospital in 1968-70.

After two years as a doctor in the U.S. Army, he completed his residency training in Dermatology at the University Of Colorado School Of Medicine in Denver in 1975.

He was board-certified by the American Board of Dermatology in 1975 and by the American Board of Pathology in 1977 for special competence in Dermatopathology.

He started practice in San Luis Obispo at the French Clinic in 1975 and has been in his private practice since 1980.

He founded the California Central Coast Dermatological Society in 1976 and remains its president. The society meets monthly to present patients and at a separate meeting to discuss the latest in dermatological literature. He is a member of numerous dermatological educational societies including the American Academy of Dermatology, American Society of Dermatologic Surgery, Tri-County Dermatologic Society, and California Medical Association.

He cares for all diseases of the skin, hair, and nails, and his main interests and expertise are in the diagnosis and treatment of skin cancer, and rashes such as psoriasis and eczema, and in the evaluation of cosmetic concerns.

He has certificates in the use of lasers, BOTOX®, and fillers such as Restylane® and RADIESSE®. He is also proficient in the use of chemical peels and has done sclerotherapy for spider veins of the legs for more than 25 years.

Joseph Diehl, M.D., FACMS, FAAD

Dr. Diehl is double board-certified in Micrographic Dermatologic Surgery (Mohs surgery) and Dermatology by the American Board of Dermatology (ABD).  He is a Fellow of the American College of Mohs Surgery (FACMS) and the American Academy of Dermatology (FAAD).

He was born and raised locally in San Luis Obispo and graduated from San Luis Obispo High School. He received his undergraduate degree from the University of California San Diego, his medical degree from UCLA, did an internship in Internal Medicine at UCLA-Olive View Medical Center, and trained in Dermatology at UCLA. He then stayed on as a full-time faculty member teaching at UCLA. 

Dr. Diehl also completed an intensive fellowship through the American College of Mohs Surgery in Mohs Micrographic Surgery and Dermatologic Oncology under the tutelage of internationally known Dr. David Kent at Dermatologic Surgery Specialists in Macon, GA, a referral center for the most difficult and recurrent cases in Middle and Southern Georgia. There he completed over 1,500 surgeries, with additional training in laser and cosmetic dermatology. He has published dozens of articles and spoken around the country on subjects including Mohs micrographic surgery, laser surgery, and medical dermatology.

Dr. Diehl specializes in the management of complex and routine skin cancers, Mohs micrographic surgery, surgical dermatology, and general adult dermatology.

He is thrilled to practice in his hometown on the Central Coast and enjoys the year-round surfing, golf, tennis, and many outdoor activities that make up the SLO Life.


Cheryl Ketelsen, Diplomate Fellow, SDPA

Cheryl Ketelsen received her undergraduate degree in Kinesiology from San Diego State University and graduated cum laude. She obtained her master’s degree in physician assistant studies from Samuel Merritt University in Oakland CA. in 2015. Before specializing in dermatology, she spent her first year working in both primary care and urgent care here in San Luis Obispo. She has currently been practicing general dermatology since 2017.

When she is not in the clinic she enjoys both international and domestic travel, learning about different cultures, hiking, snowboarding, and water sports, and spending time with her friends and family.