By Paul J. Betschart, DPM
Many foot and ankle specialists focus on the musculoskeletal conditions of patients. Skin and nail conditions of the feet, however, are some of the most common complaints that patients have. This 3-part series describes the most common conditions patients present with to my office and provide some effective treatment options. Part 1 (May 2021) focused on skin conditions. Part 2 (June 2021) focused on common nail conditions. Here we focus on issues with toenails that can reflect systemic disease.
Systemic Disease Changes
Many diseases can cause changes in the appearance and quality of the nail unit. There are entire textbooks dedicated to this subject. Here are some of the most common seen in clinical practice.
Nail dystrophy is a term describing nails that are abnormal in appearance. Typically, they can be thick, discolored, and brittle. These nail changes are most often seen in fungal nail infections (Figure 1). Systemic conditions can cause a similar appearance of the nail. Nails with this appearance that have repeated negative fungal cultures and/or fail to respond to antifungal therapy should be investigated for underlying conditions. Conditions such as psoriasis, lichen planus, Reiter’s syndrome, and sarcoidosis are examples of conditions that can result in dystrophic nails. Diagnosis can be made through history, full body examination for tell-tale skin lesions, laboratory examination, and microscopic examination of nail and skin biopsies. Managing the underlying condition can help improve the appearance of the nails. Reducing nail thickness can also improve appearance and reduce symptoms. Softening agents such as urea gel preparations can help improve nail condition and appearance. Supplementation with the B vitamin biotin can also be helpful.
Nail clubbing refers to a change in the shape of the nail and tip of the toe to resemble the end of a club. Clubbed nails are usually associated with pulmonary conditions such as COPD and cancer, as well as cardiac conditions such as congenital malformations, and endocarditis, an infection of the inside lining of the heart.
Spoon-shaped nails (Koilonychia) is a term used to describe a nail with a depressed center and upturned edges. Spoon-shaped nails can be seen with iron deficiency anemia, hemochromatosis, lupus, and nail patella syndrome.
Pigmented streaks can be a normal finding in persons with deeply pigmented skin. These longitudinal lines are usually regular with straight edges and uniform color. Melanoma skin cancer that affects the nail root area can also present with a pigmented nail streak. Suspicious signs include irregular edges, a triangular shape with the wider part at the nail root, and color variation. Suspicious nail streaks should be considered for nail unit biopsy as early detection is critical in managing this deadly malignancy.
Another longitudinal dark line of the nail unit is called the splinter hemorrhage. These thin, black lines form under the nail and can be mistaken for wood splinters. Splinter hemorrhages are commonly associated with a cardiac condition called subacute bacterial endocarditis (SBE) and are often an early presenting sign of this condition. SBE is an infection of the inner lining of the heart by slow growing bacteria. The heart growths that these infections cause can result in blood clots that can travel to distant sites, commonly resulting in blockage of nail bed arterioles which become splinter hemorrhages. Other causes of splinter hemorrhage-like discoloration are fungal infections, trauma, and psoriasis.
Transverse lines appearing on the surface of the nail are usually benign and are often related to trauma or severe systemic disease that temporarily disrupts the nail root growth. These lines will grow out with normal nail growth in 6 – 12 months. White transverse lines without a depression can be an indication of toxic exposure, particularly from arsenic.
Yellow Nail Syndrome is a rare condition where the fingernails and toenails become yellowed. The nails can be thick as well and this can be misdiagnosed as fungal infections. The exact cause of yellow nail syndrome is not clear. It is thought to be related to lymphedema, the buildup of tissue fluid in the extremities. Hereditary conditions and prior infections, such as cellulitis, can predispose a person to lymphedema due to injury to the lymphatic vessels that carry the tissue fluid back from the extremities to the central circulation. Treatment of yellow nails is usually palliative with reducing thickness and discoloration through electric grinding and application of nail conditioners such as urea gel.
Blue toenails can occur in a number of conditions. Blue discoloration of the nails and digits is usually associated with high levels of de-oxygenated hemoglobin in the peripheral circulation. Lung conditions such as COPD, asthma, and pulmonary embolism can present with blue nails. Cardiac conditions such as congestive heart failure and congenital heart defects are another cause of blue nails. They can also be related to blood abnormalities such as methemoglobinemia, polycythemia vera, and carbon monoxide poisoning.
In conclusion, toenails serve a protective role keeping the vulnerable top of the digit safe from injury (think about stubbing your toe), but they are also a window into the health of the body overall and deserve appropriate attention.
Paul J. Betschart, DPM, FACFAS, is a podiatrist in private practice in Danbury, Connecticut. A Fellow of the American College of Foot and Ankle Surgeons, his goal is to help his patients achieve optimal health from the ground up.
- Rathod DG, Sonthalia S. StatPearls: Spoon Nails. Available at https://www.ncbi.nlm.nih.gov/books/NBK559311/. Image contributed by K. Humphries.
- Kim H-J, Kim T-W, Park S-M, et al. Clinical and dermoscopic features of fungal melanonychia: differentiating from subungual melanoma. Ann Dermatol. 2020 Dec;32(6):460-465.
- Wanniang N, Navya A, Pai V, Ghodge R. Comparative study of clinical and dermoscopic features in nail psoriasis. Indian Dermatol Online J. 2020;11(1):35-40. Use is per the Creative Commons license 4.0.