1. Isolated pigmented band on a single digit that develops during fourth to sixth decade of life (although melanoma can occur in children, it is a very rare event)
2. Nail pigmentation that develops abruptly in a previously normal nail plate
3. Pigmentation that suddenly becomes darker or larger, or pigment becomes blurred near nail matrix
4. Acquired pigmentation of thumb, index finger, or large toe
5. Pigment that develops after a history of digital trauma and in which one has ruled out subungual hematoma
6. Any acquired lesion in patients with a personal history of melanoma
7. If pigmentation is associated with nail dystrophy including partial nail destruction or absence of nail plate
8. If pigmentation of periungual skin (including lateral nailfolds) is found to be present (Hutchinson’s sign); this includes pigment of cuticle or hyponychium
When A Patient Presents With Longitudinal Nail Pigmentation
Longitudinal pigmentation of the nail is a common presenting problem in general podiatry. However, it is not something the patient always brings to your attention. You need to look for it.
A 45-year-old African-American female presents to the office with a chief concern of incurvated dark nails with a history of failed treatment for fungal toenails. She recalled that her dermatologist prescribed terbinafine (Lamisil, Novartis) eight months ago but there is still discoloration over the entire nail plate on all of the nails. It turned out that she did not undergo a fungal nail culture prior to the initiation of treatment.
I performed a workup of the patient with a history and physical examination. A nail culture found no evidence of fungal hyphae.
Helpful Pointers On The Patient Workup
The physician should try and elicit a history as to whether the pigment has been present since birth or is acquired. Furthermore, the history of its duration, a history of what made the patient first become aware of it, and whether the patient has observed any change in the nail lesion may provide clues for the correct diagnosis. It is also important to look at the fingernails.
Specific questions pertaining to athletic activities, recent trauma, physical exertion such as long hiking trips or the use of blood thinners such as aspirin and warfarin (Coumadin, Bristol-Myers Squibb) may help in differentiating subungual hemorrhage from other causes of nail pigment. Obtaining a thorough medication history may help identify drugs that may contribute to abnormal nail pigmentation.1
Hutchinson’s sign is visible as an extension of the pigmentation to the proximal or lateral nail folds. It can also occur as periungual discoloration. It is an important indicator of nail melanoma.2 There are numerous conditions that produce a pseudo-Hutchinson’s sign, making the history together with the biopsy of utmost importance.1
Key Questions To Consider
1. What are the characteristic features of this condition?
2. What is the most likely diagnosis?
3. What is your differential diagnosis?
4. What does the patient workup entail?
5. When should you biopsy when faced with pigmented nails?
Answering The Key Diagnostic Questions
1. Characteristic features include nail pigmentation changes such as longitudinal bands, transverse bands and diffuse darkening.
2. Racial melanonychia
3. Fungal melanonychia, nutritional longitudinal melanonychia, traumatic longitudinal melanonychia, longitudinal melanonychia associated with inflammatory nail disorders or longitudinal melanonychia due to drugs
4. The workup entails taking a history, evaluating for Hutchinson’s sign and taking a biopsy.
5. Biopsy when the entire nail is involved, when variegated colors from light or dark brown to black are present, when the pigmented band has had recent color or width changes in Hispanic patients who have a new-onset acquired longitudinal melanonychia, even if more than one nail is affected, regardless of the age group.
What You Should Know About Racial Melanonychia
The diagnosis was racial melanonychia, a type of nail pigmentation occurring in those with pigmented skin. Melanonychia frequently has a racial predilection. It occurs among more than 50 percent of African-Americans, approximately 10 percent of Japanese people and among people of Mediterranean origin.3
Nail pigmentation changes include longitudinal bands, transverse bands and diffuse darkening. At times, there is overlap between the diffuse darkening and the longitudinal bands. The literature references longitudinal melanonychia more often because it occurs with nail melanoma, which can be deadly. The other causes of nail pigmentation are benign and are less known.