Hyperkeratotic Palmoplantar Lichen Planus in a child.

Lichen planus (LP) is a common idiopathic inflammatory disorder that affects the flexor aspect of the wrists, the legs, and the oral and genital mucosa. Depending upon the site of involvement, LP can be divided into mucosal, nail, scalp, or palmoplantar types. Palmoplantar LP can pose a diagnostic problem to the clinician as it resembles common dermatoses like psoriasis, verruca, corn, calluses, lichenoid drug eruption, and papular syphilide of secondary syphilis. In this case report, we describe a 4-year-old male child who presented with highly pruritic erythematous to violaceous hyperkeratotic papules and plaques on his palms and soles. Typical LP papules were noted on the upper back. Histopathology of the papular lesion showed features of LP. Dermatoscopy of a papule from the back showed the characteristic Wickham striae. We report this rare involvement of palm and soles in a case of childhood LP.

What was known?

Lichen planus is a common inflammatory dermatoses Palmplantar lichen planus is an uncommon variant of lichen planus.

Introduction

Lichen planus (LP)—from the Greek leichen, meaning ‘tree moss,’ and the Latin planus, meaning ‘flat’—is a chronic idiopathic inflammatory dermatoses that commonly affects the skin, hair, nails, and mucosal membranes.[1] The disease is characterized by its four ‘P's: Pruritic, polygonal, plane-topped, papules. The lesions are frequently covered with a lacy network of white scales known as Wickham striae and are typically located on the flexor aspect of the wrist, the shins, the trunk, and medial thighs.[2] The disorder is most commonly seen in middle-aged adults between 30 to 60 years of age; only 4% of cases of LP occur in children.[3] According to the dermatology literature, childhood LP with palmoplantar involvement is rare and can pose diagnostic problems for a naive physician.[4]

Case Report

A 4-year-old male child was brought to our outpatient clinic with multiple pruritic, erythematous to violaceous, flat-topped papules and hyperkeratotic plaques on his both palms and soles since the last 4 months. The parents had also noticed some violaceous raised lesions on the upper back over the same period. There was no history suggestive of hepatitis and the child had not received any vaccination recently. On examination, multiple erythematous to violaceous plane-topped papules were present on the upper back [Figure 1]. Yellowish hyperkeratotic papules and plaques were noticed on both his palms and soles, with a few of the plaques showing a central crateriform depression [Figure 2]. Oral and genital examination was normal for his age. His routine laboratory investigations, including complete blood count (Hb: 13.8 g/dl, total leukocyte count: 5600/mm3), serum chemistry (BUN: 6.0 mg/dl, creatinine: 0.4 mg/dl, SGOT: 53 IU/l, SGPT: 19.0 IU/l), and urinalysis, were normal.

Figure 1

Multiple violaceous papules on the upper back

Figure 2

Hyperkeratotic yellowish plaque on the sole showing central depression

Screening for hepatitis B and hepatitis C was negative. Dermatoscopy of a papule on his back revealed Wickham striae, whereas dermatoscopy of a plantar plaque showed a well-defined lesion topped with scales [Figures 3 and 4]. Skin biopsy was obtained from two sites (upper back and sole). Histopathology of the papule from the back showed a band- like lymphocytic infiltrate along the upper part of the dermis; vacuolar alteration of the basal layer; focal hypergranulosis; and necrotic keratinocytes, with saw tooth- like appearance of rete ridges [Figure 5]. Skin specimen from the plantar plaque showed compact hyperkeratosis, with focal parakeratosis, focal hypergranulosis, and colloid bodies [Figure 6]. A diagnosis of childhood LP with prominent palmoplantar involvement was made.

Figure 3

Lacy reticular striae (Wickham striae) seen on dermatoscopy of a lesion on the patient's back

Figure 4

Dermatoscopy of a plantar plaque showing scaling and a lacy reticular pattern

Figure 5

Hematoxylin and eosin-stained section from a papule on the back showing dense band-like infiltration in the papillary dermis, which extends to the epidermis where there is also vacuolar alteration of the basal layer, necrotic keratinocytes, irregular acanthosis, and wedge-shaped hypergranulosis (×40)

Figure 6

Hematoxylin and eosin-stained biopsy section from the sole showing compact hyperkeratosis and irregular acanthosis, hypergranulosis with a saw-tooth appearance, and upper dermal band-like inflammatory infiltration (40×)

The patient was started on oral dapsone 25 mg (2 mg/ kg) daily, along with twice daily application of clobetasol propionate 0.05% cream and emollients.

Discussion

The term lichen planus was coined by Eramus Wilson in 1869.[5] Childhood LP accounts for only 4% of all LP cases.[6] To the best of our knowledge, palmoplantar involvement in childhood LP has been only sparingly reported from the Indian subcontinent. LP can be diagnosed easily on the skin surface by its typical morphology and the characteristic Wickham striae seen on magnification. Palmoplantar LP differs from the classical lesion present at other body sites.[7] The differential diagnoses of palmoplantar LP include punctate porokeratosis, acquired palmoplantar keratoderma, calluses, verruca vulgaris, hyperkeratotic eczema, xanthomas, psoriasis, Kyrle disease, acrokeratosis paraneoplastica, arsenical keratosis, and secondary syphilis.[58]

Several morphological patterns of palmoplantar lesions in LP have been described: erythematous plaques, punctate keratosis,[9] diffuse keratoderma, ulcerative lesions, and pitted plaques.[1011] Histopathology of the lesion is essential for definitive diagnosis of palmoplantar LP; the histopathologic findings as the as in same classic LP, with basal epidermal keratinocyte damage and lichenoid-interface lymphocytic reaction, such as hyperkeratosis, wedge-shaped hypergranulosis, irregular acanthosis, necrotic keratinocyte (Civatte body), dense band-like lymphocytic infiltration in the papillary dermis, and vacuolar alteration of the basal layer.[12]

Dermatoscopy of a typical papule of LP shows the characteristic Wickham striae, which are the result of focal wedge-shaped hypergranulosis. The apparent absence of Wickham striae may be because the thickness of the horny layer obscures observation of the localized thickening of the granular layer, as happened in our case. LP has also been associated with hepatitis C virus, hepatitis B vaccination, and primary biliary cirrhosis.[1314] In our patient there was no history of any vaccination in the recent past, and serology for hepatitis C was negative.

Potent topical steroids are the mainstay of therapy for localized involvement. There has been a single report in the literature describing the efficacy of topical calcineurin inhibitor in generalized eruptive LP.[15] A short course of oral steroids (e.g. betamethasone) in tapering doses over a period of 2 weeks can substantially improve the quality of life in disabling cases of palmoplantar LP. Dapsone in a dose of 1.5-2 mg/kg can be started to maintain the patient in remission after initial control with oral steroid.

To conclude, this is the first report of childhood LP with palmoplantar involvement from Western India.

What is new?

Hyperkeratotic variant of palmoplantar lichen planus is a very rare type of lichen planus It can be commonly mistaken with common skin conditions like warts and corns.