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Erosive oral lichen planus as a sign of paraneoplastic pemphigus

Dear Editor, We read with great interest the article by Motegi et al. that appeared in the recent issue of the Journal of Dermatology. The authors described three patients with lichen planus (LP) accompanied by thymoma among 50 patients diagnosed with LP in their department, and reviewed 29 such complications in the published work. The article prompted consideration of the necessities of further investigations and proper treatment of patients with these two diseases. Nevertheless, in the mentioned patients, at least some of them were in need of excluding paraneoplastic pemphigus (PNP) or the so-called paraneoplastic autoimmune multiorgan syndrome before drawing a simple linkage between LP and thymoma. The diagnostic criteria of PNP suggested by Anhalt et al. includes: (i) painful and progressive stomatitis with preferential tongue involvement; (ii) acantholysis, or lichenoid or interface dermatitis, in histology; (iii) presence of circulating anti-plakin autoantibodies, mostly against envoplakin and periplakin; and (iv) presence of underlying lymphoproliferative neoplasm such as lymphoma, leukemia, Castleman’s disease and thymoma. Following these criteria, we presented two PNP patients in 2005, one with thymoma and the other with follicular dendritic cell sarcoma. Also in this study, autoantibodies against homologous fragments shared by these plakin proteins were detected in the culture media of these neoplasms, suggesting a possible connection between these two immunological disorders. Furthermore, in 101 PNP patients we diagnosed following the same criteria, 20 (19.8%) were accompanied by thymoma. These patients were remarkably characterized by erosive tongue and buccal mucosa and predominant hyperkeratotic erythema of the hands and feet. To our knowledge, PNP may develop LP-like, erythema multiforme-like, pemphigus-like or pemphigoid-like lesions, but these PNP with LP-like eruptions were distinct from the classical LP in that, as a part of the autoimmune syndrome, they usually show polymorphic eruptions (as both pale-reddish erythema and vesicles described in their case 1) and atypical overlapping histological features. In our 20 thymoma PNP patients, eight (44.4%) experienced dyspnea, mainly caused by bronchiolitis obliterans (similar situation as in case 16 and possibly the cause of bronchiectasis in case 29 in the published work the authors summarized) or myasthenia gravis. Considering that indirect immunofluorescence on rat bladders was only positive in 52.6% (10/19) of thymoma PNP cases (96.2% [51/53] in Castleman’s disease PNP), it would be informative if the authors performed immunoblotting or immunoprecipitation to detect anti-plakin autoantibodies to confirm or exclude the possibilities of PNP in these patients. Additionally, we suggest these immunological investigations on all recalcitrant erosive oral LP patients, which may help finding latent lymphoproliferative neoplasms including, but not limited to, thymoma.