Zosteriform Unilateral Linear Capillaritis.

Dear Editor:

Pigmented purpuric dermatoses (PPDs) are usually characterized by asymptomatic purpuric papules with pigmentation on the lower extremities1. However, these can also affect the trunk or upper extremities, and it rarely appears in linear or segmental distribution, known as unilateral linear capillaritis (ULC)2. Herein, we report a rare case of ULC that showed a zosteriform distribution on the trunk.

A 71-year-old male presented with a 6-month history of asymptomatic skin rashes spreading on his right trunk. We found multiple grouped erythematous to brownish papules and plaques with scattered petechiae along the right flank from the right abdomen (Fig. 1A). He had no traumatic history or preceding subjective symptoms. He did not have any particular medical history including cardiovascular diseases, prior use of anticoagulant drug such as aspirin, or similar family history. Laboratory evaluation showed no abnormality including complete blood count and coagulant factors. Skin biopsies revealed a band-like and perivascular infiltrate of lymphocytes with extravasation of erythrocytes in the upper dermis (Fig. 1B).

Fig. 1

Erythematous to brownish papules and plaques with scattered petechiae on the right trunk along dermatome of T9/T10 (A). Skin biopsies of samples from the right flank revealed a band-like and perivascular infiltrate of lymphocytes (B) and extravasation of erythrocytes in the upper dermis (in box). Original magnification ×200 and ×400 (H&E stain).

There are many subtypes of the PPDs, which include progressive pigmentary dermatosis, purpura annularis telangiectodes, pigmented purpuric lichenoid dermatosis of Gougerot and Blum, eczematoid-like purpura of Doucas and Kapetanakis, and lichen aureus. The most common type of PPDs is progressive pigmentary dermatosis, and its typical clinical features are asymptomatic irregularly shaped reddish-brown patches with pinhead-sized reddish puncta closely resembling “cayenne pepper” on the both lower extremities13.

Unlike to common clinical features, PPD with a segmental distribution on the lower trunk was initially reported in 1990, and several cases had been reported previously that did not fit the typical fiver subtype of PPD, called ULC, which has been known a benign condition with a tendency to spontaneously regress2. In addition, several skin disorders with a zosteriform distribution including progressive cribriform and zosteriform hyperpigmentation, and linear and whorled nevoid hypermelanosis have been reported, and differential clinical and pathologic diagnoses of those similar conditions were shown Table 145. However, as in our case, zosteriform ULC, which was clinically similar to progressive pigmentary dermatosis, except that it had zosteriform distribution, has been rarely reported. Mar et al.4 presented two pediatric cases of unilateral pigmented purpuric eruption involving the left abdomen, and Hamada et al.2 described an adult case of PPD presenting with reddish-brown purpuric papules and plaques with tiny petechiae on the left lower abdomen and femoral regions having a zosteriform distribution of L1/L2. Similarly, our case showed erythematous to brownish papules and plaques with scattered petechiae on the right trunk along dermatomes of T9/T10, but it had more clinically distinct zosteriform distribution compared with previous ones.

Table 1

Differential clinical and pathologic diagnoses of skin disorder showing zosteriform eruption

Differential diagnose	Clinical feature	Pathologic feature
Zosteriform unilateral linear capillaritis (our case)	An asymptomatic multiple grouped erythematous to brownish pigmented papules and plaques with scattered petechiae along the dermatomes of trunk	A band-like and perivascular infiltrate of lymphocytes with extravasation of erythrocytes in the upper dermis
Progressive cribriform and zosteriform hyperpigmentation	A localized, uniform, tan cribriform macular pigmentation in a zosteriform distribution without prior rash, injury, or inflammation along the Blaschko's lines of trunk or extremities	An increase in basal layer pigmentation compared with adjacent normal skin; no nevus cell and no significant difference in the number of melanocytes between both area
Linear and whorled nevoid hypermelanosis	Similar to progressive cribriform and zosteriform hyperpigmentation, but diffuse streaks and whorls of hyperpigmentation composed of homogeneously colored macules along the Blaschko's lines of trunk or extremities	An increased basal layer pigmentation and prominence or vacuolization of melanocytes without pigment incontinence

In conclusion, it is important for dermatologists to consider that PPDs could be a skin disorder showing zosteriform eruption in rare cases. Additionally, it is necessary to reassure the patients regarding the progress of the disease, because ULC has a favorable prognosis, and it more commonly resolves spontaneously without any treatment than in the other subtypes of PPDs.