Segmental vitiligo is characterized by its early onset, rapid stabilization, and unilateral distribution. Recent evidence suggests that segmental and nonsegmental vitiligo could represent variants of the same disease spectrum. Observational studies with respect to its distribution pattern point to a possible role of cutaneous mosaicism, whereas the original stated dermatomal distribution seems to be a misnomer. Although the exact pathogenic mechanism behind the melanocyte destruction is still unknown, increasing evidence has been published on the autoimmune/inflammatory theory of segmental vitiligo.
Key points
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Segmental vitiligo, a subtype of vitiligo, is characterized by its early onset, rapid stabilization, and unilateral distribution.
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It has been suggested that segmental and nonsegmental vitiligo are not 2 completely separate entities, but could represent variants of the same disease spectrum.
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Recent observational studies with respect to its distribution pattern point to a possible role of cutaneous mosaicism in segmental vitiligo.
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Good results are reported in stabilized forms of segmental vitiligo after a surgical treatment (pigment transplantation).
Clinical presentation
Clinical Signs
It is generally important to differentiate at least 2 types of vitiligo: the nonsegmental and segmental types. The nonsegmental type of vitiligo is characterized by its symmetric distribution, unpredictable course, and association with autoimmune diseases. In contrast, the segmental type has a typical unilateral distribution, is less strongly associated with autoimmune diseases, and shows a rapid stabilization. In an observational study from the authors’ group, 41/141 patients (85.4%) observed disease stabilization within the first year after onset and 8 patients (16.7%) even mentioned a stabilization in only a few days after the initial appearance of the lesions. Sometimes further progression is observed at later stages, although this is more exceptional. A study of Park and colleagues found disease recurrence in 21.8% of segmental vitiligo patients 4 or more years after disease onset.
However, most studies with long-term follow-up after pigment cell transplantation for segmental vitiligo did not show high rates of unexpected disease activity. Segmental vitiligo is associated more with an earlier age of onset compared with nonsegmental vitiligo. The reported prevalence of segmental vitiligo within a total vitiligo population varies between studies (5% and 27.9%) and was 11.6% (89/770) in the authors’ department.
Some variants of segmental vitiligo have also been described. The concomitant presence of segmental vitiligo and nonsegmental vitiligo has been termed mixed vitiligo, and if 2 segmental vitiligo lesions are present on opposite body sides, it is called a bilateral segmental vitiligo. If 2 distinct segments on the same side are present, it could be called multisegmental vitiligo. Furthermore, segmental vitiligo lesions can be present with associated halo nevi. In this article describing the distribution patterns of segmental vitiligo, halo nevi were present in 26 of 179 segmental vitiligo patients (14.4%), whereas this was even remarkably higher (24.2%; 16/65) in the authors’ study evaluating specifically segmental vitiligo lesions on the trunk. The latter might be due to the fact that the trunk is a predilection area for halo nevi.
Distribution Pattern
Segmental vitiligo has often been linked in the literature to a dermatomal distribution. However, several recent studies observed that most segmental vitiligo lesions did not fit exactly within the borders of the commonly mentioned “dermatomal” lines. It was therefore hypothesized that segmental vitiligo has probably been classified incorrectly in the past to a dermatomal distribution. However, a typical unique recurring pattern could be observed with a very clear midline demarcation. More recently, it was suggested that this recurring pattern could fit to the theory of cutaneous mosaicism. This hypothesis was also supported by the authors’ study describing convincing similarities between segmental vitiligo and other mosaic skin disorders, especially segmental lentiginosis and verrucous epidermal nevus. These observations support the possible role of cutaneous mosaicism for at least a part of the segmental vitiligo lesions.
Classification
So far, a classification of segmental vitiligo on the face (see later discussion) and the trunk (see later discussion) has been proposed. These classifications can help to predict the possible susceptible areas of future distribution of early developing segmental vitiligo lesions.
Face
The classification of segmental vitiligo on the face was determined by comparing the distribution patterns of 257 Korean patients with segmental vitiligo on the face. Six subtypes were described by this Korean group: type Ia, Ib, II, III, IV, and V ( Figs. 1 A and 2 ). Type Ia was most frequently observed (28.8%). It affects a large part of the left side of the face. Type Ia starts on the forehead at the right side of the midline and crosses the central part of the forehead, extending laterally and downwards. Overall, it resembles a reversed V-shaped pattern. Involvement of the right side of the face is rare in this subtype. Type Ib is located high on the forehead on the left or right side with frequently signs of poliosis. Type II lesions follow an archlike pattern starting from the auricular area until reaching the midline area at the philtrum. In type III , the depigmentation starts at one side of the lower lip spreading in a downwards and slightly lateral way toward the neck. Type IV closely resembles type I but does not cross the midline (unlike type 1a) and is exclusively located on the right side of the face. Finally, type V involves the right orbital area, and further spreading to the temporal area is possible. After type Ia, the most frequent subtypes were type II (16.0%), III (14.4%), IV (10.9%), Ib (10.5%), followed by type V (8.6%).
Trunk
In the authors’ retrospective observational study, the distribution pattern of 106 segmental vitiligo lesions on the trunk was analyzed and classified into 6 recurring subtypes. Type 1, 2, and 3 involved the upper part of the trunk, type 4 and 5, the middle part of the trunk, and type 6, the lower part of the trunk ( Fig. 1 B). Type 1 is a small linear band located at the central part of the upper trunk just lateral from the midline. It extends from the chin toward the sternal area. Type 2 is a depigmentation on the upper part of the shoulder running from the neck to the lateral side of the arm. Type 3 is a characteristic V-shaped pattern on the ventral side of the trunk. It starts on the lower edge of the shoulder and spreads down to the midline of the thorax. Type 4 is located below the type 3 pattern. The lesions start at the axilla and spread lateral and down until the midline. Type 5 is a horizontal bandlike lesion at the lower part of the trunk. It is located above the waist and expands to the lateral side of the trunk. Type 6 presents as a rectangular depigmented area, which also develops on the lower part of the trunk, although it can extend below the waist. Type 6 can mostly be observed on the abdomen. It is similar to the checkerboard pattern as described by Happle.
Type 3 was the most common observed segmental vitiligo pattern and can easily be recognized by its “triangle shape,” which can be observed on the upper trunk against the midline of the upper thorax. This specific pattern (type 3) has also been reported in other mosaic disorders, such as segmental lentiginosis and epidermal nevus verrucosus. Furthermore, the distribution of a triangle-shaped lesion on the upper part of the trunk resembled a combination of the type 1b (broadband Blaschko linear) and type 2 pattern of mosaicism as described by Happle.
Segmental vitiligo was more frequently observed on the ventral side (85.9%) compared with the lateral part (52.8%) or back (36.8%) of the trunk; this may reflect the migration pattern of the melanoblasts during embryogenesis from their origin in the neural crest. Most melanocyte precursors migrate dorsolaterally and proliferate while they travel through the dermis until they reach the ventral midline. As such, melanocytes at the ventral side of the body could be at increased risk for acquiring somatic mosaicism due to their increased proliferation until they reside in their final destination at the epidermis or hair follicle.
Clinical presentation
Clinical Signs
It is generally important to differentiate at least 2 types of vitiligo: the nonsegmental and segmental types. The nonsegmental type of vitiligo is characterized by its symmetric distribution, unpredictable course, and association with autoimmune diseases. In contrast, the segmental type has a typical unilateral distribution, is less strongly associated with autoimmune diseases, and shows a rapid stabilization. In an observational study from the authors’ group, 41/141 patients (85.4%) observed disease stabilization within the first year after onset and 8 patients (16.7%) even mentioned a stabilization in only a few days after the initial appearance of the lesions. Sometimes further progression is observed at later stages, although this is more exceptional. A study of Park and colleagues found disease recurrence in 21.8% of segmental vitiligo patients 4 or more years after disease onset.
However, most studies with long-term follow-up after pigment cell transplantation for segmental vitiligo did not show high rates of unexpected disease activity. Segmental vitiligo is associated more with an earlier age of onset compared with nonsegmental vitiligo. The reported prevalence of segmental vitiligo within a total vitiligo population varies between studies (5% and 27.9%) and was 11.6% (89/770) in the authors’ department.
Some variants of segmental vitiligo have also been described. The concomitant presence of segmental vitiligo and nonsegmental vitiligo has been termed mixed vitiligo, and if 2 segmental vitiligo lesions are present on opposite body sides, it is called a bilateral segmental vitiligo. If 2 distinct segments on the same side are present, it could be called multisegmental vitiligo. Furthermore, segmental vitiligo lesions can be present with associated halo nevi. In this article describing the distribution patterns of segmental vitiligo, halo nevi were present in 26 of 179 segmental vitiligo patients (14.4%), whereas this was even remarkably higher (24.2%; 16/65) in the authors’ study evaluating specifically segmental vitiligo lesions on the trunk. The latter might be due to the fact that the trunk is a predilection area for halo nevi.
Distribution Pattern
Segmental vitiligo has often been linked in the literature to a dermatomal distribution. However, several recent studies observed that most segmental vitiligo lesions did not fit exactly within the borders of the commonly mentioned “dermatomal” lines. It was therefore hypothesized that segmental vitiligo has probably been classified incorrectly in the past to a dermatomal distribution. However, a typical unique recurring pattern could be observed with a very clear midline demarcation. More recently, it was suggested that this recurring pattern could fit to the theory of cutaneous mosaicism. This hypothesis was also supported by the authors’ study describing convincing similarities between segmental vitiligo and other mosaic skin disorders, especially segmental lentiginosis and verrucous epidermal nevus. These observations support the possible role of cutaneous mosaicism for at least a part of the segmental vitiligo lesions.
Classification
So far, a classification of segmental vitiligo on the face (see later discussion) and the trunk (see later discussion) has been proposed. These classifications can help to predict the possible susceptible areas of future distribution of early developing segmental vitiligo lesions.
Face
The classification of segmental vitiligo on the face was determined by comparing the distribution patterns of 257 Korean patients with segmental vitiligo on the face. Six subtypes were described by this Korean group: type Ia, Ib, II, III, IV, and V ( Figs. 1 A and 2 ). Type Ia was most frequently observed (28.8%). It affects a large part of the left side of the face. Type Ia starts on the forehead at the right side of the midline and crosses the central part of the forehead, extending laterally and downwards. Overall, it resembles a reversed V-shaped pattern. Involvement of the right side of the face is rare in this subtype. Type Ib is located high on the forehead on the left or right side with frequently signs of poliosis. Type II lesions follow an archlike pattern starting from the auricular area until reaching the midline area at the philtrum. In type III , the depigmentation starts at one side of the lower lip spreading in a downwards and slightly lateral way toward the neck. Type IV closely resembles type I but does not cross the midline (unlike type 1a) and is exclusively located on the right side of the face. Finally, type V involves the right orbital area, and further spreading to the temporal area is possible. After type Ia, the most frequent subtypes were type II (16.0%), III (14.4%), IV (10.9%), Ib (10.5%), followed by type V (8.6%).
Related posts:
The Medical Treatment of Vitiligo
Quality of Life, Burden of Disease, Co-morbidities, and Systemic Effects in Vitiligo Patients
Skin Cancer Risk (Nonmelanoma Skin Cancers/Melanoma) in Vitiligo Patients
Surgical Therapies for Vitiligo
Depigmentation Therapies for Vitiligo
Vitiligo Pathogenesis and Emerging Treatments
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