An Unusual Cause of Lichen Striatus in a Young Boy.

Sir,

Lichen Striatus (LS), also known as blaschkitis, is an uncommon, self-limiting dermatosis characterized by pink–purple papules arranged in a linear pattern that follows Blaschko’s lines. Lesions are mostly asymptomatic or mildly pruritic and predominantly involve extremities. The exact etiology of the eruption remains unknown, but it is thought that genetic, infectious, and environmental factors may be involved. Case reports have incriminated varied causes including BCG and hepatitis B vaccination, and even trauma.

A 11-year-old boy presented with complaints of minimally itchy, linear rash over the posterior aspect of left lower limb, extending from buttocks to the medial malleolus. Lesions had initially appeared as erythematous papules about 3–4 months back, behind the left knee, and then subsequently spread proximally to the buttock and distally to the medial malleolus, over the next 2 months and then stabilized, to assume the present dimensions. About 2 months before the manifestation of the dermatosis, he had suffered multiple monkey bites over his left calf [Figure 1]. He was given an injection of tetanus toxoid and 5 doses of anti-rabies vaccine (Rabipur) as per the schedule. He underwent regular dressing and wound care. Wounds healed well with minimum scarring.

Figure 1

Monkey bite over left leg

Dermatological examination revealed a linear eruption comprising multiple, small, erythematous, slightly scaly papules extending from the left buttock to the left medial malleolus [Figure 2]. There were no lesions elsewhere on the body and no intra-oral changes. Histopathology from the lesion demonstrated epidermis lined by stratified squamous epithelium showing focal spongiosis and vacuolar alteration of the basal layer. Superficial dermis showed moderate, perivascular inflammatory infiltrate of lymphocytes admixed with histiocytes. Occasional melanophages were seen in the papillary dermis [Figure 3]. Based on clinical and histological findings, he was diagnosed as LS. The patient was placed on a once-daily application of 0.05% fluticasone propionate cream.

Figure 2

Lichen Striatus over left lower limb

Figure 3

Focal Spongiosis in the epidermis with band-like lymphocytic infiltrates in the dermis (H and E stain, magnification ×100)

Although Senear and Caro described it way back in 1941, its etiology still remains uncertain.[1] A study of 115 children could propose precipitating or causal factors only in five patients; triggering factors included infection, cutaneous injury, and hypersensitivity.[2]

It has been proposed that a cross-reactivity between viral proteins used in the vaccines and shared epitopes on keratinocytes could be the trigger for cell-mediated attack by cytotoxic T cells in vaccine-associated cases of LS.[3]

Some researchers suggests that LS shows cutaneous mosaicism due to somatic mutations that produce abnormal keratinocyte clones during early embryogenesis, and these aberrant clones may remain silent until a triggering event causes a break in immunologic tolerance that initiates an autoimmune response.[4]

Isolates from simian bites have shown a predominance of alpha-hemolytic Streptococci, Enterococci, Staphylococcus epidermidis, and many anaerobes.[5] Since a monkey bite causes infections as well as trauma and both are known to trigger LS, it is possible that the monkey bite could have acted as a trigger for LS in our case.

Monkey bites are known to transmit viral and bacterial diseases. However, despite monkey bites accounting for 1.7–3.2% of animal bites in India, no case of LS after simian bite has been reported; so a causal relationship is unlikely.[6] We present this case to emphasize the possibility of such cases being missed, given the sheer number of animal bites the world over.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient’s guardian (since the patient is a minor) has given his consent for his son’s images and other clinical information to be reported in the journal. The guardian understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.