Vitiligo is a common pigmentation disorder characterized by the loss of skin color, occurring when pigment-producing cells (melanocytes) are destroyed or stop functioning. This results in depigmented, white patches on the skin, which can also affect hair and mucous membranes. While there is no cure, treatment options exist to manage the condition and encourage repigmentation. Vitiligo is categorized into subtypes, and understanding the differences between the two primary forms, segmental and non-segmental vitiligo, is important for effective management.
Segmental and Non-Segmental Vitiligo Defined
Non-segmental vitiligo (NSV), also called generalized vitiligo, is the most common form, accounting for 85% to 95% of all vitiligo cases. It is characterized by depigmented patches that typically appear on both sides of the body in a relatively symmetrical pattern. The patches often begin small and may gradually expand, covering extensive areas of the skin, commonly affecting the hands, feet, face, and areas around body orifices.
Segmental vitiligo (SV) is the less common form, representing about 5% to 16% of cases, and follows a different pattern. This type is distinctly localized and unilateral, meaning the patches appear only on one side of the body. SV distribution often follows a dermatome—an area of skin supplied by a single spinal nerve—resulting in a sharply demarcated, asymmetrical appearance.
Contrasting Physical Characteristics and Spread
The most striking difference between the two forms is the physical distribution of the patches. NSV is defined by a bilateral and symmetrical pattern, where patches may appear on both elbows or both knees simultaneously. In contrast, SV is unilateral and asymmetrical, with the white patches limited to one side of the body, often forming a band-like pattern following a nerve path.
The age of onset also differs, providing an important clinical distinction. SV typically appears much earlier in life, often during childhood or adolescence, with many cases beginning before the age of ten. While NSV can begin at any age, it tends to manifest later, usually becoming apparent in late adolescence or early adulthood.
The progression and stability of the lesions are the most significant functional differences between the two types. SV often progresses rapidly for a short period (sometimes only a few months) before reaching stability, where the patches do not spread further. NSV, however, is characterized by an unpredictable, chronic course with periods of stability interspersed with episodes of active progression and recurrence.
Etiology and Associated Health Concerns
The underlying biological mechanisms driving these two forms are distinct, explaining their varied clinical presentations. NSV has a strong association with systemic autoimmunity, where the immune system mistakenly targets and destroys the melanocytes. This systemic dysfunction means NSV frequently occurs alongside other autoimmune disorders, such as thyroid disease, pernicious anemia, and Type 1 diabetes.
Conversely, SV is hypothesized to have a neurogenic, or nerve-related, mechanism rather than a systemic autoimmune one. The localized, dermatomal pattern suggests that dysfunction or damage in the sympathetic nerves may release toxic mediators. These mediators, such as pro-inflammatory neuropeptides, could cause the targeted destruction of melanocytes in that specific segment of skin. The absence of a systemic immune trigger means SV is rarely associated with other autoimmune diseases, unlike NSV.
Type-Specific Treatment Strategies
The difference in stability and underlying cause dictates different management strategies for each type. Because NSV is an active, widespread, and potentially progressive autoimmune condition, treatment focuses on systemic and broad-area therapies aimed at halting disease progression. These approaches include narrowband ultraviolet B (NB-UVB) phototherapy, which stimulates repigmentation over larger areas, and topical or systemic immunomodulators to suppress the immune attack.
SV’s localized nature and tendency to stabilize make it less responsive to the systemic medical therapies used for NSV. Once the condition is confirmed stable (typically for six to twelve months), surgical options become a more viable and effective approach. Procedures like autologous melanocyte transplantation, which involves grafting healthy pigment cells from an unaffected area onto the white patch, are often favored for stable, localized SV lesions.