A birthmark is a common skin irregularity that is present at birth or develops shortly afterward. These lesions are formed by an overgrowth of normal skin components, such as pigment cells, blood vessels, or glands, that developed incorrectly during embryonic formation. Since the scalp is a hair-bearing region of skin, birthmarks frequently occur there, often involving hair follicles and surrounding structures. The presence of a birthmark on the scalp can lead to visible differences in the hair growing from that area. While most are harmless, understanding the specific type of birthmark is useful for proper observation and care.
Specific Types of Birthmarks Found on the Scalp
One type of lesion frequently found on the scalp is the Nevus Sebaceous, classified as a hamartoma, a benign overgrowth of mature tissue. At birth, this lesion typically appears as a hairless, slightly raised plaque ranging from pale pink to yellowish-orange. Its texture is often smooth or waxy during infancy, with well-defined borders separating it from the surrounding skin.
Congenital Melanocytic Nevi (CMN) are pigmented moles arising from a proliferation of melanocytes. These birthmarks vary widely in size and display shades of brown, tan, or black. CMN may have a smooth or slightly rough surface, and unlike Nevus Sebaceous, they often present with notable hair growth.
Vascular birthmarks, caused by an abnormal collection or formation of blood vessels, also appear on the scalp. Infantile hemangiomas, sometimes called “strawberry marks,” are red or purplish lesions that grow rapidly during the first few months of life before shrinking and fading by the time a child reaches school age. A Port-Wine Stain (nevus flammeus) is a flat, permanent capillary malformation presenting as a pink, red, or violaceous patch that does not fade over time.
Impact on Hair Follicles and Growth
A birthmark’s presence on the scalp disrupts the normal architecture of the skin, leading to changes in hair growth patterns. For Nevus Sebaceous, the malformation involves an overgrowth of sebaceous glands and a lack of mature hair follicles within the lesion. This structural abnormality results in a permanent, localized patch of alopecia, or hair loss, where the birthmark is located.
The abnormal skin tissue within the Nevus Sebaceous actively suppresses hair growth through cellular signaling. Sebaceous gland cells in the lesion release growth-suppressing bioactive factors, such as Fibroblast Growth Factor-5 (FGF-5). This chemical signaling inhibits the survival and function of dermal papilla cells and outer root sheath cells, which are necessary for developing new hair shafts.
Conversely, Congenital Melanocytic Nevi (CMN) are associated with hypertrichosis, meaning excessive hair growth within the lesion. The hair growing from CMN is frequently coarser, darker, and longer than the surrounding scalp hair. The melanocytic cells cluster around the hair follicle structures, stimulating the production of terminal, mature hair.
Monitoring and When to Consult a Specialist
Consultation with a healthcare professional, such as a dermatologist or pediatrician, is recommended for proper diagnosis and risk assessment, even though most scalp birthmarks are benign. Certain birthmarks, particularly Nevus Sebaceous, require long-term observation because they have a small potential to develop secondary tumors later in life; most of these tumors are benign. During adolescence, hormonal changes can cause a Nevus Sebaceous to become more raised, bumpy, or wart-like, a transformation that should be documented by a specialist.
Any birthmark on the scalp or elsewhere should be monitored for signs of change that could suggest a rare malignant transformation. These warning signs include:
- Rapid growth
- New-onset bleeding
- Ulceration
- Dramatic change in color, texture, or border irregularity
Large or giant Congenital Melanocytic Nevi also require careful, lifelong monitoring due to a slightly increased, though overall still low, risk of developing melanoma.
A specialist can also discuss elective removal options, which are often considered for cosmetic reasons or to eliminate the small risk of secondary tumor development in lesions like Nevus Sebaceous. Early diagnosis is useful for vascular birthmarks, as some infantile hemangiomas that are growing quickly or are located near sensitive areas may benefit from early medical management. An expert evaluation ensures that the birthmark is not associated with any underlying systemic conditions, which is a rare but important possibility for certain types of large or multiple lesions.