Pediatric Dermatology
Lichen Planus: An Update and Review
Lichen planus (LP) is a papulosquamous eruption of the skin, scalp, nails, and mucous membranes. Although LP is more common in adults, it has...
Comment
Kaposi first described LPP in 1892 and used the term lichen ruber pemphigoides to describe a case of typical LP together with a widespread bullous eruption. Lichen planus pemphigoides is characterized by tense blisters that arise on lesions of LP as well as on skin unaffected by LP. In contrast, bullous LP blisters are confined to LP lesions only and occur from intense lichenoid inflammation and extensive liquefactive degeneration of basal keratinocytes. The vesicle formation in LPP is a result of autoantibodies to the bullous pemphigoid (BP) antigen BPAg2, which can be explained by the epitope spreading epiphenomenon whereby epidermotropic cytotoxic T cells damage the basal keratinocytes in LP by targeting unknown epidermal antigens, resulting in the exposure of BP180 and therefore instigating the autoimmune response.1 The process of epitope spreading takes months to develop; the mean duration of LP before LPP is 8 weeks in children and 12 weeks in adults,2 which is comparable to the current case.
Pathogenesis
Lichen planus pemphigoides usually is idiopathic; however, there have been cases reported in association with various medications including calcium channel blockers such as diltiazem, Chinese herbs,3 simvastatin,4 ramipril,5,6 captopril,7 psoralen plus UVA phototherapy,8 and cinnarizine.9 In addition, in a case-controlled study, the use of neuroleptics or diuretics was found to be a risk factor for LPP development.10
This case is unique because it shows an association of LPP with an intrauterine pregnancy. Despite the fact that we did not perform the required studies to determine the exact cause, there probably exists an association between LPP and the pregnancy, as the patient presented with a 5-month history of severe LP prior to vesicle formation. The patient only developed the vesicular lesions during pregnancy, which were later controlled with systemic steroids and then recurred postpartum only as LP lesions, suggesting that the patient’s pregnancy may have contributed in the pathogenesis as an inducing factor. We suspect that the LP was aggravated by the pregnancy and continued to worsen, so much as to cause epitope spreading and lead to the bullous eruption at the end of the first trimester.2
Differential Diagnosis
Initially, we suspected a diagnosis of pemphigoid gestationis (PG), previously known as herpes gestationis. The classic presentation of PG starts with an intense pruritus followed by the emergence of pruritic urticarial papules and plaques in the umbilical or periumbilical areas. The lesions may become targetlike or polycyclic and may spread to other areas of the trunk, arms, and legs, often including the palms and soles.11-15 Just as in our case, vesicles and bullous lesions appear at both the site of the urticarial plaques as well as on normal skin.16 The clinical features noted in our patient that were not typical of PG included the multiple lesions on the face and inside the nostrils. Only 20% of PG cases are associated with mucosal involvement,11,12,15 and there are no documented reports of PG occurring in a patient with LP, according to a PubMed search of articles indexed for MEDLINE using the search terms pemphigoid gestationis, herpes gestationis, and lichen planus.
Lichen planus pemphigoides can be easily differentiated from BP. Lichen planus pemphigoides occurs in younger patients, with a mean age of 35 years, unlike BP, which commonly affects elderly men.17 Lichen planus pemphigoides also is less severe and has a better response to treatment than BP. It also affects the palms and soles, which are rarely affected in BP. There are no reports in the literature of BP developing during pregnancy, according to a PubMed search using the terms bullous pemphigoid and pregnancy. However, LPP and BP share a common antibody, the BP180 antigen, and differences exist in the epitope where the antibody binds in each condition.18,19
Diagnosing LPP
In LPP, DIF typically shows linear deposits of IgG, IgM, IgA, fibrinogen, and C3 along the BMZ, of which IgG and C3 are most commonly seen.3 Our patient had linear deposition of C3, IgM, and IgA along the BMZ, which excluded bullous LP from the differential diagnosis. Bullous LP is not an autoimmune condition but rather is on the severe spectrum of LP where Max Joseph spaces become so large so as to lead to vesicle and bullae formation. In addition to the linear deposit at the BMZ, LPP typically reveals immunoglobulin (mainly IgM but also IgA), C3, and fibrinogen staining of colloid bodies in the papillary dermis on DIF; however, some cases of LPP only present with a linear deposition of C3 along the BMZ, which is why, similar to PG, these diagnoses by DIF are similar. Direct immunofluorescence of PG reveals linear IgG1 and IgG3 along the BMZ. IgG1 and IgG3 immunoglobulins are known to fix complement better than other immunoglobulins, thus linear C3 along the BMZ is the most consistently positive immunoreactant. Less common positive immunoreactivity with the same pattern has been seen with IgA, IgM, C1, and C4 (Table).14,15,18 The lack of linear IgG and the presence of IgM is more suggestive of LPP.
