Sean Schreckengast

Sean joined the Clinic for Special Children in 2024 as a Laboratory Scientist I. He is responsible for running several clinical assays including amino acid quantification by HPLC and DNA isolation from whole blood.  He also performs targeted mutation detection through Sanger sequencing and high resolution melting curve analysis.

Before joining the Clinic, he worked at Eurofins Lancaster Laboratories as a Scientist. In his free time, he enjoys playing guitar, playing video games, and spending time with friends and family. He also enjoys rooting for all Philadelphia sports teams, especially the Phillies!

Why are you passionate about the Clinic?

I am passionate about the Clinic because it represents the good that science can do in the community. The work done here is incredibly impactful and, in some cases, life-saving. It is truly a special place, and I believe it will continue to have a beneficial impact on the community for years to come.

Sean’s Credentials


  • 2023  Messiah University, Bachelor of Science in Biochemistry

Professional Experience

  • 2023 – Eurofins Lancaster Laboratories, Scientist

Published Papers

To view Sean’s peer reviewed published papers, please visit our Published Papers page HERE.

Alanna Koehler, PhD

Alanna Koehler, PhD, joined the Clinic for Special Children as its first Assistant Laboratory Director in 2022, bringing extensive training in biomedical sciences and genetics.

As the Assistant Laboratory Director, Dr. Koehler is responsible for assisting the Laboratory Director, Dr. Erik Puffenberger, in managing the biochemical and genetics laboratory at the Clinic. Dr. Koehler works on a blend of hands-on laboratory work, data analysis, and scholarly work. She also develops and validates new clinical assays/tests and writes clinical laboratory reports.

Dr. Koehler spends most of her free time with her rescue dogs and she cares deeply for senior and special needs animals. She also loves to read and is constantly learning new things.

Why are you passionate about the Clinic?

I have been passionate about the Clinic since I was first introduced to its mission as an undergraduate researcher at Franklin & Marshall College. CSC brings the academy and world-class clinical care to a rural setting, redefining “accessibility” by making sure the patients receive diagnostics and care when they need it, in a location that is convenient and comforting, from providers they trust, and at a cost they can afford. The clinicians and research/laboratory teams are making incredible strides in early disease detection and intervention, cutting down on hospital stays and medical costs while improving quality of life for patients. I am truly grateful to be part of such a caring, innovative, and hardworking team!


Dr. Koehler’s Credentials


  • 2022  University of California San Diego, Doctor of Biomedical Sciences
  • 2015  Franklin & Marshall College, Bachelor of Arts in Neuroscience

Professional Associations

  • American Society for Human Genetics (ASHG), member
  • American Society for Cell Biology (ASCB), member


  • 2021-2023 San Diego Fellowship (training grant), University of California San Diego
  • 2021  Award Lecture, Department of Pathology Research Retreat, University of California San Diego
  • 2015-2017  Intramural Research Training Award Fellowship, National Institutes of Health
  • 2015 Charles N. Stewart Neuroscience Award, Franklin & Marshall College
  • 2015  Graduated cum laude, Franklin & Marshall College
  • 2011  George Washington University Engineering Medal

Published Papers

To view Dr. Koehler’s peer reviewed published papers, please visit our Published Papers page HERE.

KaLynn Loeven

KaLynn joined the Clinic for Special Children in 2017 as a Laboratory Technician and in 2019 she was promoted to a Laboratory Scientist II.  She is responsible for performing genetic research through microarrays and development of new testing assays.

KaLynn earned both a Bachelor of Science degree in chemistry in 2009 and a Bachelor of Arts Degree in Biology in 2010 from Saint Francis University in Loretto, PA.  Prior to joining the Clinic, she was employed as a senior chemist working in the method feasibility/development of pharmaceutical raw materials at Eurofins Lancaster Laboratories.  Originally from the Reading area, she enjoys living in Lancaster with her husband.

Why are you passionate about the Clinic?

The Clinic struck me as a unique opportunity to combine my skills in the laboratory with a motivation to serve.  As I learned more, I felt excited to become a part of a team which combines patient care and genetic research to improve the quality of life for a vulnerable population.

Erik G. Puffenberger, PhD

Dr. Puffenberger received a B.A. in biology from Swarthmore College in 1987, and a Ph.D. in human genetics from Case Western Reserve University in 1996. He worked as an editorial assistant for Dr. Victor McKusick’s Mendelian Inheritance in Man (1987-1991), as a senior laboratory techician for Dr. Clair Francomano (1988-1991), and received his Ph.D. under the direction of Dr. Aravinda Chakravarti (1991-1996). He joined the clinic staff in January 1998, and became Laboratory Director in 2000.

Dr. Puffenberger was raised in Elizabethtown, Pennsylvania. His father was an ordained minister in the Church of the Brethren and taught religion and philosophy at Elizabethtown College. His mother was born and raised in the Shenandoah Valley of Virginia and is descended from many Mennonite pioneer families. From an early age, Erik was interested in genealogy and spent many hours as a teenager at the Lancaster Mennonite Historical Society. This early interest developed into a strong passion for genetics, which was his favorite area of study at Swarthmore College.

After college, he could not decide whether to attend medical or graduate school, so he chose to spend a gap year working in the field of genetics to help him select a career path. In 1988, he accepted a position with Dr. Victor McKusick as an editorial assistant for Mendelian Inheritance in Man, a catalogue of human genetic diseases and traits. That gap year at Johns Hopkins Hospital turned into a four-year experience which also included genetic research in the laboratory of Dr. Claire Francomano. One of the projects he worked on during this time was the first description of fibrillin gene mutations as a cause of Marfan syndrome. The research of Drs. McKusick and Francomano focused significantly on the Amish of Lancaster County. As such, Erik spent many hours compiling Amish pedigrees for these studies, and frequently accompanied the researchers on field trips to Pennsylvania and Ohio. These experiences helped cultivate his interest in founder populations.

Although his parents began to doubt he would ever return to school, Erik enrolled in graduate school in 1991 at the University of Pittsburgh to study human genetics with Dr. Aravinda Chakravarti. He knew Dr. Chakravarti through collaborations with genetic researchers at Johns Hopkins, and Dr. Chakravarti had a large NIH grant to study the genetics of Hirschsprung disease. Ironically, as Erik began work in the laboratory, he discovered that a sizable collection of Hirschsprung disease families in the Chakravarti study were Mennonites from Lancaster County. He began to study them exclusively, and made dozens of field trips to Lancaster to recruit more families. Eventually, thirty-two families were used to genetically map and identify the cause of Hirschsprung disease in these families. During these studies, Dr. Chakravarti moved his laboratory to Case Western Reserve University in Cleveland, OH, where Erik received his Ph.D. in 1996.

Following graduation, Erik did a brief post-doctoral fellowship with Dr. Chakravarti. It was during this fellowship that he became acquainted with Dr. D. Holmes Morton and the Clinic for Special Children. After several discussions, the clinic offered him a position as laboratory scientist and he began work in January 1998. By joining the clinic and leaving academic research, most of his peers and mentors warned that he was committing professional suicide. However, Erik recognized the potential benefits of applying molecular genetics to patient care, particularly in founder populations like the Amish and Mennonites. Since the clinic was not using any genetic technologies at the time, he quickly began to build the genetic capabilities of the clinic laboratory. In 2000, he assumed the role of Laboratory Director. Today, his work involves implementation of molecular techniques for routine diagnosis, research into the genetics of isolated populations, development of molecular strategies for newborn screening, and identification of novel disease genes by genetic mapping and exome sequencing.

Why are you passionate about CSC?

The clinic represents a unique amalgam of cutting-edge genetic research and comprehensive medical care. This novel paradigm can be found in few places. I am proud and passionate about the work we do, the patients we help, the lives we impact, and the science we produce. There is never a boring day, and I am constantly challenged to learn and grow as a person and scientist. There surely is no geneticist on the planet who has a more rewarding career than I do. I am especially proud to work with talented professionals who tirelessly provide a medical home for patients with complicated and sometimes deadly disorders. I cannot imagine performing this important, meaningful work with a better group of colleagues.