What’s New in Nail Anatomy? Pterygium: What and Where is It?

My quest continues as I search out all the newest facts about nail anatomy. I’m working with world-class medical experts and internationally known nail educators, in addition to constantly reviewing scientific reports/books. In this update, I’d like to share some new information in hopes of ending the confusion about the basic structure of the natural nail. This is the second in a series about the nail anatomy.

In that update, you’ll find a nail cross-section diagram that reveals much about the natural nail; including the source of the cuticle tissue from the very thin layer of stem cells found on the underside of proximal nail fold (aka PNF). The proximal nail fold is the entire flap of skin covering the matrix, extending from the edge of the visible nail plate to the first joint of the finger.

You’ll also learn that the eponychium (means “upon the nail”) is the only tissue that covers the new growth of nail plate and is the home of stem cells that make all the cuticle tissue. Also, that the outer layer of the proximal nail fold is covered with tissue whose surface can become keratinized when damaged/injured and will hardened to create a highly protective shield that can resist attack by infectious organisms or potentially harmful chemicals. After reading the last update, many wrote to ask, “What about pterygium? What and where is it?”

What is Pterygium?

Medical literature defines pterygium (terr-idge-ee-uhm) as any abnormal growth of skin that becomes stretched into a wing-like shape. In other words, unless the skin is abnormal and stretched, it is NOT pterygium. This word should NEVER be used to describe the cuticle or any normal growth of skin. Educators, please make sure you use and teach about this term correctly.

Medical literatures describe that describe the multi-step process that creates pterygium. Even so, I couldn’t find any diagrams that demonstrates how it develops. To my knowledge, the diagram below is the first of its kind to visually depict this complex series of events.

Don’t make the common mistake of thinking that pterygium is just an “overgrowth of cuticle”. That is NOT correct! Researchers who study these problems believe pterygium occurs because the proximal nail fold becomes fused to the nail matrix. This fusion continues and progresses as shown, often until all the matrix is destroyed. Once the entire proximal nail fold is fused with the remaining nail plate, the slow, continued nail growth pulls and stretches the proximal nail fold into a triangular shape. This fusion process may continue until eventually most or all the matrix is destroyed. During these final stages, stretched skin become painful, the nail plate becomes thinner and if the matrix is completely destroyed– then new nail plate can no longer be made, and eventually the nail plate will be replaced by the proximal nail fold. There is no known way to stop or reverse the process.

The nail matrix/PNF fusion is thought to be triggered by injury or disease, e.g. burns, physical trauma, overly aggressive manicure and pedicure techniques, lichen planus, psoriasis or other medical conditions. Allergic reactions may also be the cause. Repeatedly contacting the proximal nail fold with any type of artificial nail coating materials, including all UV curing gels or monomer liquid and polymer powder formulations, can increase the risks of adverse skin reactions to the proximal nail fold and sidewalls. Any conditions with an unhealthy appearance should be referred to a doctor for examination. Pterygium should not be cut away by nail technicians, since it can bleed and become infected. It can be softened and conditioned, e.g. hot oil manicures.

Final Thoughts: The proximal nail fold is NOT the cuticle. Normally, the thin layer of cuticle tissue on the nail plate sits between the proximal nail fold and nail plate to create an important barrier (seal) against bacteria. This protects the nail matrix from infections that could lead to permanently damaged nail plates and if left unchecked could spread to infect the bone. Similar infection can occur to the proximal nail fold and other tissues surrounding the nail plate. Cutting and overly aggressive manicure/pedicure techniques of this area can break the tissue seal, allowing bacteria to penetrate and causing a nail to become infected. This is why it is important to carefully manicure/pedicure these areas.

Nail technicians should NOT be intentionally abrading or cutting skin around the nail plate. Some might believe and teach the keratinized skin on the proximal nail fold is dead and safe to cut. This is NOT correct! The underlying tissue contains microscopic capillaries/nerves that are often broken by cutting or using e-files. Pathogens (infectious organisms) can gain entry thought this damaged tissue and this can lead to infections. AND, this damaged skin is significantly more likely to become permanently allergic to nail coating products through repeated exposure. Clearly, it is NOT in the client’s best interest to intentionally cut or abrade the proximal nail fold. The same advice applies for pterygium—this is NOT overgrown cuticle tissue. Don’t make this mistake!

Please help clear up the confusion, share this information widely. Be sure to know the proper nail anatomy terms and use them correctly. Teach your clients and other nail professionals the facts. It’s time for the confusion to end.

Want to learn more? I Make It Easy!

You can get much more information from my three-part book series, “Face-to-Face with Doug Schoon”, Vol. 1-3. Each book is very different and crammed with essential information that all nail technicians should understand in order to work properly and safely. Don’t be fooled by myths and misinformation or marketing exaggerations.

Get the facts from a scientist who knows them. Learn more about how nail products work, and why they sometimes don’t work. All three books are available world-wide on Amazon, iTunes, Kobo and Nook as either a printed or e-book. Read them all- you’ll be amazed by what you will learn.

Doug Schoon is a leading scientific researcher specializing in the Science of Keratin; including Nails, Hair and Eyelashes.