A case of unilateral blaschkoid lichen planus pigmentosus.

Dear Editor,

Lichen planus pigmentosus (LPP) is a rare variant of lichen planus.[1] A few cases of LPP involving linear, blaschkoid, and zosteriform patterns have been reported in the literature.[2-4] We herein describe a case involving a 48-year-old female patient with unilateral abdominal involvement of LPP following the lines of Blaschko.

A 48-year-old female patient was admitted to our clinic with a 2-year history of a pruritic rash localized to the right half of the abdomen. The patient's medical history revealed that she had been using levetiracetam and levothyroxine for 8 years to treat epilepsy and hypothyroidism. On dermatologic examination, livid-brown, S-shaped, and linear-patterned macules and papules were observed from the right half of her abdomen to the right lumbar area with a tendency to coalescence (Figure 1). Mucous membranes, scalp, and nails were not affected. The results of routine laboratory tests were all within normal limits. Histopathological examination of a punch biopsy specimen from the lesions revealed hyperkeratosis, epithelial atrophy, hydropic degeneration in the basal layer, civatte bodies, band-like lymphocytic infiltrates, and pigment incontinence in the papillary dermis (Figure 2). A diagnosis of unilateral blaschkoid LPP was made based on the clinical and histopathological evaluations.

Figure 1

A. Livid-brown, S-shaped, and linear-patterned macules and papules. B. Close-up of the lesion

Figure 2

Hyperkeratosis, epithelial atrophy, hydropic degeneration in the basal layer, civatte bodies, bandlike lymphocytic infiltrates, and pigment incontinence in the papillary dermis (Hematoxylin & eosin X10)

LPP is differentiated from classic lichen planus. In contrast to the shiny, purplish papules and plaques seen in classic lichen planus, LPP is characterized by dark brown-gray macules, patches, and occasionally papules. Furthermore, the mucosa, scalp, and nails, which are the sites at which lichen planus is frequently localized, are generally not involved in LPP. Although the histopathological findings are similar, melanin incontinence is more prominent in LPP than in classic lichen planus. It is also differentiated from zosteriform LPP by the absence of dermatomal involvement.[1,2] LPP tends to be localized in sun-exposed areas, such as the head and neck, as well as in flexor areas, such as the axillary, inguinal, and submammary regions. However, only a few cases of LPP involving Blaschko's lines have been reported.[2-4]

In 2004, Hong et al. were the first to report two cases of LPP that presented as unilateral LPP with a linear pattern: one was localized on the leg and the other on the arm.[5] Seo et al. later reported another case of linear LPP involving a 60-year-old male patient with a history of gastric cancer who developed unilateral involvement on his neck and chin.[1]

Akarsu et al. were the first to report a case of LPP with unilateral Blaschkoid involvement of the trunk.[2] A 16-year-old female patient developed lesions in her submammary and pectoral areas. She had no history of drug intake, sun exposure, or trauma, and she did not exhibit mucosa or nail involvement. Dossi Cataldo et al. reported a second case with LPP with Blaschkoid distribution in a patient with three clinical subtypes.[4] Vineet et al. presented a third case of LPP with lesions lateralized to the right side of the body along the lines of Blaschko in a linear and zosteriform pattern.[3]

The present report describes the fourth case of LPP on the trunk following the lines of Blaschko. The patient had been using levetiracetam and levothyroxine for 8 years to treat epilepsy and hypothyroidism. However, we did not consider that the LPP had been induced by these medications or by the concomitant diseases because of the prolonged history and histopathological findings. Additionally, our patient did not have nail or mucosa involvement, similar to the other cases reported.[2-4]

Blaschkoid LPP may be confused with erythema dyschromicum perstans, linear and whorled nevoid hypermelanosis, incontinentia pigmenti, actinic lichen planus, lichen striatus, and Riehl's melanosis. Because clinical differentiation is not always possible, histopathological assessment is recommended.[2]

This case was deemed worthy of presentation because of the rarity of the condition and the fact that this is the fourth reported case of blaschkoid LPP localized on the trunk.