Lichen Planus Pemphigoides Associated With Pregnancy Mimicking Pemphigoid Gestationis
Lichen planus pemphigoides (LPP) is a rare condition characterized by tense blisters that arise on lesions of lichen planus (LP) and on unaffected skin. We present the case of a 25-year-old pregnant woman at 12 weeks’ gestation who developed an acute bullous eruption after 5 months of worsening LP. Similarities to pemphigoid gestationis (PG) included lesions around the periumbilical area and multiple urticarial erythematous papules and plaques in addition to linear C3 and IgM deposition along the basement membrane zone (BMZ) on direct immunofluorescence (DIF).
Practice Points
- Lichen planus pemphigoides (LPP) is characterized by tense blisters that arise not only on lichen planus lesions such as bullous lichen planus but also on skin unaffected by lichen planus.
- In LPP, the autoantibodies specifically target the MCW-4 epitope of the NC16A4 domain of the bullous pemphigoid antigen BPAg2, distinguishing it from other autoimmune blistering diseases against the NC16A domain.
The differential diagnosis of the subepidermal autoimmune blistering diseases associated with antibodies against BP180, including BP, LPP, and PG, often is challenging.15 However, LPP can now be distinguished by immunological studies including immunoblot analysis of the immunodominant region of NC16A of the BP180 antigen and the immunoglobulin subclass that reacts to 180-, 200-,20 and 230-kDa antigens within the BMZ (Table).15,18-20 The Table summarizes the different autoantibodies, antigens, and epitopes to distinguish subepidermal autoimmune blistering diseases.
Despite not performing these studies in our patient, we concluded that the clinical, histological, and DIF findings of this case are more consistent with LPP than with the other subepidermal blistering diseases. However, we cannot exclude the possibility of the patient having a new entity with a unique antibody from epitope spreading.
Conclusion
We present a case of lichenoid papules and plaques consistent with LP, with the development of vesicles and bullae after the first trimester of pregnancy. The clinical, pathologic, and DIF findings were highly suggestive of LPP. Although the exact pathogenic mechanism is not fully known, we suspect that pregnancy may have contributed to the origin of the disease. Further evaluation of pregnant patients with lichenoid lesions who develop blisters are needed for the elucidation of the mechanism, which may be secondary to epitope spreading that led to new autoantibody formation.
