Lichen myxedematosus (LM), also called papular mucinosis, was first described by Dubreuilh1 in 1906 and later classified by Montgomery and Underwood2 in 1953. LMs are a group of localized or generalized papular eruptions of unknown etiology categorized as cutaneous mucinoses in which dermal mucin deposition is the distinctive histologic feature.3-5 LM has no relation to endocrine gland disorders, particularly thyroid disease.2,3,6 In their landmark paper, Montgomery and Underwood2 classified 4 clinical types of LM: (1) generalized lichenoid papular eruption, which is also called scleromyxedema, (2) discrete papular form, (3) localized to generalized lichenoid plaques, and (4) urticarial plaques and nodular eruptions that usually evolve into the generalized lichenoid form. In 2001, Rongioletti and Rebora6 updated the classification system. The articles by Montgomery and Underwood2 and Rongioletti and Rebora6 both agree with the existence of the discrete papular form, also called discrete papular LM (DPLM). According to Rongioletti and Rebora,6 DPLM has only been reported in the medical literature 8 times,1,2,7-12 This is unlike scleromyxedema, the most common type of LM, which has been documented in more than 110 cases.6 In this case report, we describe an interesting case of DPLM that was localized to the neck of our patient, and we review the English medical literature.
Case Report
An 80-year-old black woman presented to our clinic with a 2-month history of a pruritic eruption localized to her neck. Multiple topical steroids and antihistamines had been used without any decrease in the eruption or the pruritus. The woman's medical history was significant for gastric cancer status post a partial gastrectomy 7 years prior, pseudotumor cerebri, hypertension, and osteoporosis. She is followed regularly for these conditions, which are stable. Her medications included acetazolamide, atenolol, nifedipine, rabeprazole sodium, fluoxetine, oxybutynin chloride, alendronate sodium, docusate calcium, and a multivitamin. Prior to the onset of this eruption, the patient had a change in the acetazolamide formulation, which was initially thought to be the culprit. Although she returned to the original formulation for longer than a month, she had no resolution of the symptoms. At that time, she sought evaluation in our clinic. On physical examination, multiple 2- to 4-mm discrete, flesh-colored shiny papules without scale were present over the patient's bilateral and posterior neck (Figure 1). Results of 2 punch biopsies showed splaying of the collagen with mucin present diffusely throughout the dermis. No increase in the number of fibroblasts was seen (Figure 2). Results of colloidal iron stain showed positive results in the papillary dermis and showed mucin mildly throughout the deep dermis (Figure 3), supporting the diagnosis of LM. Complete blood count, chemistry panel, liver function, thyrotropin, and serum protein test results were all within reference range. Pimecrolimus cream has been effective in treating our patient's pruritus. We have followed her for 14 months, and the lesions have remained localized to her neck, with continued normal thyrotropin and serum protein values.
Comment
In 2001, Rongioletti and Rebora6 revised the classification system of LM, categorizing it into 3 broad subsets: (1) generalized papular and sclerodermoid, (2) localized LM, and (3) atypical forms. The first subset, generalized papular and sclerodermoid, represents scleromyxedema. Diagnosis requires a generalized papular and sclerodermoid eruption, monoclonal gammopathy (paraproteinemia), no evidence of thyroid dysfunction, and a histologic triad of fibroblast proliferation, fibrosis, and mucin deposition.6 Scleromyxedema is associated with many systemic disorders that may include numerous organ systems.6,13 Although spontaneous resolution has been reported,14 scleromyxedema typically is a long-term and disfiguring disease6,13 associated with variable morbidity and mortality.15,16 The criteria for diagnosing the subset of localized LM requires a papular eruption, deposits of mucin with variable fibroblast growth, absence of paraproteinemia, and absence of thyroid dysfunction.6 There are 5 subtypes6: DPLM,2,7-9,17-21 acral persistent papular mucinosis (APPM),22-27 cutaneous mucinosis of infancy,28-31 self-healing papular mucinosis (SHPM),32-36 and nodular LM.37,38 All subtypes show small, firm, waxy papules limited to a few areas of the skin, which may coalesce and form nodules or plaques. DPLM can involve any site on the body. APPM exclusively involves both extensor surfaces of the distal upper extremities. Cutaneous mucinosis of infancy is a pediatric variant of DPLM or APPM. SHPM has spontaneous resolution. Nodular LM is characterized by a predominance of nodules.6 All subtypes except for SHPM typically persist long-term. Systemic symptoms were only reported in SHPM.32,33 In general, localized LM is self-limited and associated with a good prognosis.6 The histologic features of LM are summarized in Table 1.5 The pathology lies within the dermis for all types of this disease, and the epidermis is essentially normal.5 The types of LM can be distinguished from one another by 3 histologic clues: (1) mucin distribution pattern, (2) dermal level of mucin deposits, and (3) some extra findings.5 Differentiation can be additionally aided by observing the number of fibroblasts. Common mucin stains include colloidal iron, mucicarmine, and alcian blue at pH 2.5 (but not pH 0.5); common metachromatic mucin stains include toluidine blue, thionine, and methylene blue.3