Pityriasis Lichenoides Chronica Presenting With Bilateral Palmoplantar Involvement

Pityriasis lichenoides is an uncommon, acquired, idiopathic, self-limiting skin disease that poses a challenge to patients and clinicians to diagnose and treat. Several variants exist including pityriasis lichenoides et varioliformis acuta (PLEVA), pityriasis lichenoides chronica (PLC), and febrile ulceronecrotic Mucha-Habermann disease. Precise classification can be difficult due to an overlap of clinical and histologic features. The spectrum of this inflammatory skin disorder is characterized by recurrent crops of spontaneously regressing papulosquamous, polymorphic, and ulceronecrotic papules affecting the trunk and extremities. Pityriasis lichenoides is a monoclonal T-cell disorder that needs careful follow-up because it can progress, though rarely, to cutaneous T-cell lymphoma. In this case report we describe a patient with a rare presentation of PLC exhibiting bilateral palmoplantar involvement and mimicking psoriasis. We review the literature and discuss the clinical course, pathogenesis, and current treatment modalities of PLC.

Case Report

A 61-year-old woman presented with a recurrent itchy rash on the legs, feet, hands, and trunk of several months’ duration. Her medical history included Helicobacter pylori–associated peptic ulcer disease and hypertension. She was not taking any prescription medications. She reported no alcohol or tobacco use or any personal or family history of skin disease. For many years she had lived part-time in Hong Kong, and she was concerned that her skin condition might be infectious or allergic in nature because she had observed similar skin lesions in Hong Kong natives who attributed the outbreaks of rash to “bad water.”

Physical examination revealed reddish brown crusted papules and plaques scattered bilaterally over the legs and feet (Figure 1); serpiginous scaly patches on the hips, thighs, and back; and thick hyperkeratotic psoriasiform plaques with yellow scale and crust on the palms and soles (Figure 2). The nails and oral mucosa were unaffected. Histopathologic evaluation of the lesions obtained from the superior aspect of the thigh showed parakeratotic scale and a lichenoid lymphocytic infiltrate in the papillary dermis consistent with PLC (Figure 3).

Figure 1. Erythematous crusted and hyperkeratotic papules over the left shin (A) and dorsal aspect of the left ankle and foot (B).

Figure 2. Thick hyperkeratotic plaques involving the sole of the left foot.

Figure 3. Skin biopsy demonstrated parakeratotic scale with underlying superficial chronic inflammation and hemorrhage (A) (H&E, original magnification ×10). High-power view demonstrated thick parakeratotic scale, a lichenoid lymphocytic infiltrate in the papillary dermis, and vacuolar change of the basal layer with occasional individual cell necrosis (B) (H&E, original magnification ×20).

The patient was started on tetracycline 500 mg twice daily for 10 days and on narrowband UVB (NB-UVB) therapy at 350 J/cm² with incremental increases of 60 J/cm² at each treatment for a maximum dose of 770 J/cm². She received 9 treatments in total over 1 month and noted some improvement in overall appearance of the lesions, mostly over the trunk and extremities. Palmoplantar lesions were resistant to treatment. Therapy with NB-UVB was discontinued, as the patient had to return to Hong Kong. Given the brief course of NB-UVB therapy, it was hard to assess why the palmoplantar lesions failed to respond to treatment.

Comment

Subtypes

Pityriasis lichenoides is a unique inflammatory disorder that usually presents with guttate papules in various stages of evolution ranging from acute hemorrhagic, vesicular, or ulcerated lesions to chronic pink papules with adherent micalike scale. Two ends of the spectrum are PLEVA and PLC. Papule distribution often is diffuse, affecting both the trunk and extremities, but involvement can be confined to the trunk producing a central distribution or restricted to the extremities giving a peripheral pattern. A purely acral localization is uncommon and rarely has been documented in the literature.¹

Pityriasis lichenoides et varioliformis acuta typically presents with an acute polymorphous eruption of 2- to 3-mm erythematous macules that evolve into papules with a fine, micaceous, centrally attached scale. The center of the papule then undergoes hemorrhagic necrosis, becomes ulcerated with reddish brown crust, and may heal with a varioliform scar. Symptoms may include a burning sensation and pruritus. Successive crops may persist for weeks, months, and sometimes years.²

Febrile ulceronecrotic Mucha-Habermann disease is an acute and severe generalized eruption of ulceronecrotic plaques. Extensive painful necrosis of the skin may follow and there is an increased risk for secondary infection.² Systemic symptoms may include fever, sore throat, diarrhea, and abdominal pain. Febrile ulceronecrotic Mucha-Habermann disease has a mortality rate of 25% and should be treated as a dermatologic emergency.²

Pityriasis lichenoides chronica has a more gradual presentation and indolent course than PLEVA. It most commonly presents as small asymptomatic polymorphous red-brown maculopapules with micaceous scale.³ Papules spontaneously flatten over a few weeks. Postinflammatory hypopigmentation or hyperpigmentation may persist once the lesions resolve. Similar to PLEVA, PLC has a relapsing course but with longer periods of remission. Pityriasis lichenoides chronica usually involves the trunk and proximal extremities, but acral distributions, as in our case, have been described. This rare variant of pityriasis lichenoides may be underrecognized and underdiagnosed due to its resemblance to psoriasis.¹

The prevalence and incidence of PLC in the general population is unknown. There appears to be no predominance based on gender, ethnicity, or geographical location, and it occurs in both children and adults. One study showed the average age to be 29 years.²