Nails. They’re a handy surface to decorate; they help us pick up objects, scratch an itch and protect our fingers and toes.
But did you also know that nails can tell us a lot about your health and your well-being?
For most of us, fingernails are completely renewed in about six months.
That means that our nails are a six-month medical record incomparable to any physical exam component. A window into our metabolic soul…
Take a second and check them out now.
What do you see? Are they smooth, without pits or grooves? Are they uniform in color, strong, and free of spots and discoloration?
In my practice, I check everyone’s nails — preferably unpolished! And when I see something interesting and useful, I’ll file the pictures and track changes over time. Watching the changes of nails can let us know we’re on track with treatment. In this blog I want to share with you a few interesting cases, hopefully inspiring you to take a look at your own nails and to add this easy and useful investigation to the routine physical examination of your patients.
Anatomy of a nail
Image from Freethought Forum.
Nails are comprised primarily of the sulfur-rich protein, keratin, derived from tightly packed keratinocytes, the main cell type of the epithelium. Keratin is a highly biosorbent compound — it readily binds many essential and toxic metals and other chemicals. (UB biochemistry students: see the keratin protein structure below.) In fact, while writing this blog, I stumbled upon a rather nifty green chemistry paper looking at the feasibility of using modified keratin-rich chicken feathers for cleaning toxic waters. Great idea!
The human nail is thought to reflect total body status of many nutrients. Toxic, or imbalanced, levels of certain compounds can displace the normal distribution of nutrients in the nails, as well. We would expect, therefore, that such changes might be reflected visually.
“The nail growth, color, structure, and composition can vary by influence of several factors as nutritional and toxicological aspects, diseases and infections, gender, and age. All these indications make the human nail a potential source of information of the body status.”
“Virtually every nutritional deficiency can affect the growth of the nail in some manner.”
Further, we would also expect that nutrient-influenced nail changes to be relatively common, given the widespread evidence of nutrient insufficiencies and toxin presence.
Amazingly — but not surprisingly — doctors were keenly aware of the utility of the nail physical exam prior to the introduction of routine laboratory analysis. Indeed, some of our richer resources come from publications released in the early 20th century.
Biochemistry students: Look at the alpha helix and beta pleated sheets of keratin. The sheets are held together by hydrogen bonding. Cysteine (actually, cystine) is abundant in keratin, comprising up to 24% of total amino acid content. Therefore, many disulfide bridges are present in keratin, making it very ridged and stable.
This is the image of the thumb nail of a 60-year old woman presenting with inflammatory arthritis. The nail is slightly yellow, and prominent vertical ridging (onychorhexis) and white bands (leukonychia striata) are noted.
Onychorrhexis can be a normal variant — many of us have subtle ridging. However, when we see it more pronounced, especially when accompanied with brittle features, we can consider nutrient deficiencies, including protein and minerals. The leukonychia may point to specific deficiencies in selenium or zinc. Finally, the yellow color change (after ruling out smoking or recent nail polish) can be seen in autoimmunity, including rheumatoid arthritis; pulmonary disease and infection. Vitamin E may help to reverse yellowing.
A 16-year old girl presented with koilonycha, a spooning of the nails. This condition is commonly associated with iron deficiency, but zinc deficiency may also cause it. Her labs revealed very low zinc status, followed by a low-normal ferritin (iron status), but no anemia. Seshadri (see link below) mentions scurvy (vitamin C deficiency), pellagra (niacin deficiency), and riboflavin deficiency, as other possible causes of koilonychia. Protein malnutrition may also contribute.
A 63-year old woman presented with severe hand eczema with trachyonychia (20-nail dystrophy). Trachyonychia is a fairly common finding in those with hand eczema, ichthyosis vulgaris and alopecia areata. It’s also quite challenging to reverse. Her nutrient deficiencies included minerals zinc, selenium, copper and manganese; vitamins B12, folate and D.
After much work “inside-out” (improving diet and nutrient status), as well as “outside-in” (building her epidermal barrier), her hand eczema improved. Some months later, her nails grew back normally. The barrier work using fatty acids, occlusive and humectant topicals, as well as bleach baths, were essential to success. Needless to say, she was thrilled with the change, and relieved to be off the steroid merry-go-round.
Hand eczema in my experience isn’t so responsive to the “inside-out” approach that can work miracles with an atopic dermatitis that spares the hands. Hand eczema is often associated with a mutation in the epidermal barrier protein filaggrin.
Another pearl I’d like to mention is the relationship between osteopenia/osteoporosis and nail changes. If you observe brittle nails in a post-menopausal woman or an older man, check bone density. And, as bone density improves, observe the nails get stronger, too.
A few notes on well-being and nails: A cursory glance at your patient’s nails may reveal onychotillomania (nail picking) or onychophagia (nail biting). Such findings can be good openers for a chat about stress and anxiety. Improved well-being often correlates with favorable nail changes.
I encourage you to continue your exploration into nails and nutrients. Here’s a nice table with a link to the full text paper below.