Today’s post describes the possible causes of the appearance of spots on the nails. These very often have a linear shape and are caused by what we technically call “longitudinal melanonychia”.
In my experience as a dermatologist, these are spots that tend to cause some discomfort. They can appear suddenly and last a long time, or they can stay for a long time. These lines can be caused by many things. Among them, the most feared is melanoma, which is rare in the nail, but with serious consequences. This is why it is important to consult a dermatologist (either in person or as an online dermatologist) when a spot appears on the nail.
Why do spots appear on the nail?
The appearance of brown spots on the nail can have several causes, most of which are not serious. In some cases, the stains may have a linear appearance that remains over time. Below is a list of the most common causes of discoloration:
- Racial pigmentation: People with brown or black skin may naturally have more pigmented lines on their nails. They are often seen on more than one fingernail and toenail. They can appear at any age, even in children. There is no health risk.
- Punctures: Sometimes we see irregular spots that may be more reddish or black in color after a blow or repeated minor trauma (such as wearing a tight shoe). They usually appear abruptly, sometimes with pain, and disappear as the nail grows. They are usually small bruises (which turn brown) under the nails. Sometimes they can be an increase in pigmentation.
- Medications: Some medications can cause increased pigmentation of the nails. The change usually occurs some time after starting the medication and usually appears on more than one nail.
- Pregnancy: During pregnancy, some nails may become more pigmented or brown lines may appear.
- Some skin conditions: psoriasis, fungal infections, warts, or other less common tumors may cause brown lines to appear on some nails.
- Some general diseases and syndromes: some endocrinological diseases, among others, can be accompanied by linear spots on the nails. Peutz-Jeghers and Laugier-Hunziker syndromes present these spots on the nails, usually accompanied by spots on the lips. A doctor can help diagnose all of these conditions, which usually have symptoms other than nail spots.
- Moles or melanoma: These brown lines can be the expression of a mole or a melanoma located in the nail matrix. Most often it is a mole (nevus), which is a benign spot. However, especially in adults, it is important to make sure that it is not a melanoma, which has a much worse prognosis.
Warning signs of a spot on the nail
Of all the possibilities mentioned in the previous section, the one that should undoubtedly make us more alert is that the spot in question is due to a nail melanoma. This is rare. It accounts for less than 3% of melanomas in fair-skinned people, although its frequency is higher in darker-skinned people, where it can account for up to 30% of melanomas. The prognosis of melanoma of the nail is poor, so it is very important to consult a dermatologist when in doubt. It is important to take into account some details that can be particularly alarming:
- Being an adult: Children are much less at risk. In them, the line is most likely due to a mole or melanocytic nevus.
- Line width greater than 4 mm.
- Different shades of brown in the line.
- Changes in color or size over time.
- Observation that the skin surrounding the nail is also pigmented (this is called Hutchison’s sign, which you can see in this photo).
- Changes in the nail itself, with breakage, ulceration, or irregularity of the nail.
- A family history of melanoma.
Importance of seeing a dermatologist
ou may be familiar with a case that went viral on Facebook some time ago. It was about a girl who was diagnosed with melanoma of the nail. She insisted on the need to consult a dermatologist in case of any nail lesion. She hoped that her experience could help others…so let’s take note!
Consulting a dermatologist online is fast, convenient and useful. It can provide reassurance and guidance if you don’t have access to a dermatologist in person. However, in the specific case of a nail stain, if you have the option, I advise you to do it in person (I work as a dermatologist in Madrid, if you find it useful, you can find me here). This way the professional will be able to evaluate your spot with dermatoscopy.
