Discrete Papular Form of Lichen Myxedematosus: A Case Report and Review of the Literature

DPLM is a subtype of localized LM.2,6 Although the lesions can involve any site, DPLM is typically distributed symmetrically to the trunk and limbs. The skin lesions have been described as a variable number of firm, smooth, waxy, or flesh-colored papules 2 to 5 mm in size. Normal serum protein and thyroid function test results verify the diagnosis of DPLM.6 Because Montgomery and Underwood2 originally defined LM as having no relation to any endocrine gland disturbance, we recommend additional random chemistry panel or fasting blood glucose laboratory tests if there is any question that a patient may have diabetes mellitus. Histologically, DPLM may have a diffuse or local pattern of mucin distribution involving the upper and mid reticular dermis. The involved dermis typically shows edema. The amount of fibroblast proliferation is variable. When compared with scleromyxedema, DPLM has no collagen deposition or sclerosis and a lesser amount of fibroblast proliferation.5-7 Some argue that DPLM and APPM are closely related variants.25,27 However, we believe that DPLM and APPM are distinct subtypes of localized LM. DPLM typically affects men (Table 2) and its lesions may be erythematous, larger, and include areas other than the distal upper extremities.4,23,24 In comparison, APPM has an overwhelming female-to-male ratio of 4.7:1.6 APPM also exclusively involves the back of the hands, extensor surface of the wrists, and sometimes the distal forearms.4,6,23 Histologically, APPM typically has more focal mucin deposits, which spare a subepidermal grenz zone, and a normal number of fibroblasts; DPLM has mucin deposits that are more diffuse (compared with APPM), have a variable number of increased fibroblasts, and have an irregular arrangement of collagen bundles.4-6,23

Table 2 summarizes the main features of the 10 DPLM cases reported in the English medical literature.2,7-9,17-21 Our criteria required there be no evidence of paraproteinemia, no history or laboratory evidence of any endocrine disease, no history of human immunodeficiency virus infection, histologic proof of dermal mucin deposits, and specific gross descriptions consistent with DPLM. It should be noted that only 4 of the 8 DPLM cases originally cited by Rongioletti and Rebora⁶ were included in Table 2. Four cases were excluded because 2 reports were written in French,1,12 1 report included a patient with diabetes mellitus,10 and another did not perform a necessary laboratory test to rule out thyroid disease.11 Other cases were excluded because they did not fulfill our criteria.39,40 Among the 10 DPLM patients summarized, 7 were men. The mean age of the group was 51.3 years. Only 3 of the 10 cases reported information on the patient's ethnicity: one was Caucasian,7 one was Asian,8 and our patient was African American. Nine of the 10 cases reported no evidence of paraproteinemia. The single case2 that did not report this finding was published before an association between LM and paraproteinemia was known in the 1960s.41 All 10 cases reported thyroid function test results within reference range. Only 3 of the 10 patients had symptomatic skin lesions, which were mainly pruritus. No systemic symptoms were noted. Three of the 10 patients had solitary skin lesions on areas other than the typical trunk and limbs. One patient had skin lesions only on his lumbar region, another had facial lesions, and our patient had lesions on her neck. Seven of the 10 patients had comorbid medical disorders, including hypertension, migraines, psoriatic erythroderma, psoriasis, seizures, gastric cancer in remission, pseudotumor cerebri, osteoporosis, and hepatitis C. Only hepatitis C was comorbid with more than one DPLM patient.17,20 This may be a coincidence because one patient developed DPLM after contracting hepatitis C,20, while the other patient developed it before contracting hepatitis C.17 Psychiatric illness was limited to depression and was found in 2 cases.20,21 No DPLM cases progressed to scleromyxedema, and none have been reported in the literature.5,6 DPLM rarely resolves on its own. Spontaneous resolution did not occur in any of the 10 reported DPLM cases, and only 2 patients were treated successfully. In Reynolds et al,18 the patient responded to therapy with intralesional corticosteroid injections and flurandrenolide-impregnated tape. In Kaymen et al,19 a patient was treated with a CO2 laser and postoperative intralesional corticosteroid injections. There was no growth after one year. All the other DPLM cases did not have effective therapy, lacked specific details of improvement, or did not report this information.2,7-9,17,20,21 Only Tay and Khoo,8 Enerback and Mobacken,9 and Kaymen et al19 commented on which therapies failed (oral thyroxine, topical corticosteroids, and shave excision, respectively). Our patient complained of persistent itching that did not respond to initial treatment with topical steroids and antihistamine medications. She later received pruritic relief with pimecrolimus cream therapy. However, the skin lesions remained. To our knowledge, this is the first report of pimecrolimus therapy in the treatment of pruritis secondary to DPLM. It is difficult to treat a rare disease such as DPLM when the pathogenesis is unknown, and many treatments have failed. Fortunately, DPLM and the other localized forms of LM are usually self-limited to the skin and have very little or no morbidity, leading some experts to believe that the disorder is unnecessary to treat.6 We believe that treatment is sometimes helpful. In our patient, the DPLM lesions were pruritic and located at a cosmetic area of the neck. The patient and dermatology staff decided to pursue a treatment plan. Therefore, even though localized LM lesions are typically benign, sometimes it is beneficial to treat them, especially if they cause irritating symptoms or cosmetic issues. 

Conclusion