Lichen Myxedematosus: Strict Classification and Diagnostic Criteria are Still Lacking.

Sir,

We read with interest the article by Thomas et al., recently published in the Indian Journal of Dermatology.[1] In this article, the authors described a case of lichen myxedematosus (LM) and classified it as “an atypical scleromyxedema (SM)” based on the criteria proposed by Rongioletti and Rebora.[2] According to this classification, typical SM should fulfill the following criteria: (1) Generalized papular and sclerodermoid eruption; (2) mucin deposition, fibroblast proliferation, and fibrosis; (3) monoclonal gammopathy; and (4) absence of thyroid disease. Based on the presence of all criteria except monoclonal gammopathy, the authors have classified their patient as an atypical case of SM. We do not agree with this confusing classification that considers a case presenting with cutaneous involvement only in otherwise healthy patient, a form of SM, the most severe form of LM with chronic, potentially fatal course as shown by many authors.[12] Hence, it seems critical to re-evaluate the previously mentioned diagnostic criteria and classification.

We suggest that the typical skin lesions (firm, waxy, closely set papules that may coalesce into indurated nodules, or plaques), whether localized or generalized, and the typical histopathologic features of diffuse dermal mucin deposition and fibroblast proliferation are constant findings in all cases of LM and are necessary for the diagnosis of this rare disorder. On the other hand, features such as monoclonal gammopathy, thyroid disorder, peripheral eosinophilia (as shown in this article), HIV, and hepatitis C virus[3] are variable associated findings that were reported in some patients and to which any new emerging finding or association can be added.

We believe that the presence of monoclonal gammopathy should not be considered as a must for the diagnosis of SM because it was evident in only 80% of the reported cases, its exact relationship to the pathogenesis of the disease is not yet defined, and it does not correlate with either extension or progression of the disease.[4] Similarly, we do not agree that the absence of thyroid disease is a must for the diagnosis of SM because the cutaneous lesions in thyroid dermopathy are completely different from the typical waxy papules of LM, previously described in association with many thyroid disorders.[3]

We propose that further classification of LM should depend on the presence or absence of systemic manifestations that indicates the severity of the condition and could distinguish clearly between a severe form with systemic, even, lethal manifestations (SM), and a pure cutaneous, nondisabling form. Going with our concept, Pomann and Rudner[5] have reported that some authors used less stringent criteria for the diagnosis of SM, omitting the requirement of a monoclonal gammopathy and lack of thyroid disorder.

Accordingly, we suggest that the severity of LM can be graded into three categories: G1 (mild) which includes cases presenting with limited (localized) cutaneous lesions, G2 (moderate) which includes cases presenting with extensive (generalized) cutaneous lesions and, G3 (severe) which includes cases presenting with localized or generalized cutaneous lesions and extracutaneous, systemic manifestations (SM). According to these proposed diagnostic criteria and severity grading system of LM, the presented case can be classified as “pure cutaneous LM, moderate severity (G2)” due to the presence of extensive skin lesions in the absence of systemic manifestations.

We hope that these criteria would help to simplify the diagnosis of the disorder, to clearly define its different presentations, to allow easy classification of the newly reported cases, and to choose the most suitable regimen for each case.

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Conflicts of interest

There are no conflicts of interest.