Lichen myxedematosus (LM) is a chronic cutaneous mucinosis that can present as a localized skin lesion or as a generalized systemic disease termed scleromyxedema. The differential diagnosis is determined by a combination of clinical presentation, serological studies, and histopathological examination. Currently, well-established and accepted histopathological features to distinguish localized LM from scleromyxedema have not been elucidated. Our recent publication, together with a retrospective literature review, suggests that the presence of groups of light chain-restricted plasma cells represents a distinct histopathological clue for the diagnosis of localized LM. In this report, we provide two additional cases of localized LM with lambda light chain-restricted plasma cells, together with clinical and histopathological findings that are similar to our previous publication. These cases support our theory that the light chain-restricted plasmacytic microenvironment is primarily attributed to the pathogenesis of localized LM. Therefore, we consider these cases to constitute a clinically and pathologically new variant of localized LM and name it primary localized cutaneous LM with light chain-restricted plasma cells.

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UNASSIGNED: In reticular erythematous mucinosis, (1) the presence of dotted vessels and (2) uniform, structureless, yellowish-white spots, and patches on dermoscopy correspond to histopathological findings of (1) vessels at the tips of the dermal papillae and (2) thickening and rupture of the collagen and fiber bundles with mucin deposition, respectively.
UNASSIGNED: Reticular erythematous mucinosis is a rare form of skin mucinosis that primarily affects middle-aged women, typically appearing as papules and plaques in the upper chest or midline of the back. Here, we report the case of a 75-year-old woman with skin papules and plaques left untreated for 8 years. A gross skin examination was followed by histopathological and dermoscopic examinations. The main dermoscopic findings were (1) dotted vessels and (2) uniform structureless yellowish-white spots and patches. The corresponding histopathological findings were (1) vessels at the tips of the dermal papillae and (2) thickening and rupturing of the collagen and fiber bundles with mucin deposition, respectively. Laboratory investigations revealed normal results, ruling out various autoimmune disorders. REM was diagnosed based on these findings. The study presents relevant evidence-based findings in dermatology and cutaneous pathology as it is the first description of REM using dermoscopy. Dermoscopic diagnosis without other unnecessary tests would benefit both the clinician and the patient.

BACKGROUND: Acral persistent papular mucinosis (APPM) is a rare idiopathic subtype of localized lichen myxedematosus. To date, there have been 40 APPM cases reported worldwide; however, only 7 cases have been reported in the Korean literature.
METHODS: A 70-year-old man was referred to our hospital with a solitary pinkish nodule on the dorsum of his right hand. Despite the absence of symptoms, the patient wanted to know the exact diagnosis; thus, a biopsy was performed. Histopathological examination of a biopsy specimen obtained from the nodule on the dorsum of his hand revealed orthokeratotic hyperkeratosis with patchy parakeratosis, prominent hypergranulosis, and diffuse dissecting mucinous deposition between collagen bundles, along with some bland-looking spindle cells throughout the dermis. The nodule was histologically diagnosed as an APPM, and an intralesional triamcinolone injection (2.5 mg/mL) was started every 2 wk. After three sessions of treatment, the patient showed marked improvements.
CONCLUSIONS: To the best of our knowledge, this is the first case of a Korean APPM presenting as a solitary nodule that showed a marked response to triamcinolone intralesional injection. Since it is a rare disease, we report this case to contribute to future research on the pathogenesis and treatment of APPM.

Cutaneous mucinoses are a diverse group of diseases that are occasionally seen in the context of an adverse drug reaction. We report the case of a 59-year-old male who presented with an asymptomatic, acneiform rash on his forehead, scalp, nose, upper chest, and upper back that had developed after treatment with erlotinib therapy used in the treatment of metastatic tonsillar sinus squamous cell carcinoma. Biopsy of these lesions demonstrated atypical histology that had features of both follicular mucinosis and myxedema. This histologic phenomenon is a rare drug reaction that has not previously been described in association with erlotinib.

Cutaneous mucinosis is a rare disease that manifests as an excessive accumulation of mucin in the skin that forms waxy papules or plaques. We report a case of a 44-year-old male psoriatic patient who developed generalized cutaneous mucinosis after 11 months of biological treatment. The patient had a history of psoriasis for 20 years and had been treated with narrow-band UVB phototherapy, methotrexate, or acitretin intermittently. He was started on etanercept after he was diagnosed with psoriatic arthritis, and 11 months later, he complained of swelling in his extremities and myxoid cysts on his fingers. Etanercept was then discontinued due to loss of efficacy and widespread skin lesions. However, the lesions subsided spontaneously after 6 months without specific systemic treatment.

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BACKGROUND: Primary cutaneous mucinosis are a heterogeneous group of diseases characterized by the deposition of glycosaminoglycans in the dermis and the follicles. These diseases are rare in children therefore their diagnosis and management are still challenging. Joint involvement has been reported in patients with secondary cutaneous mucinosis and, rarely, in primary mucinosis. We describe a case of Cutaneous Mucinosis of Infancy with joint involvement.
METHODS: An healthy 5-year-old boy showed acute arthritis of the left knee and left elbow confirmed by ultrasound. Laboratory tests were within normal range. Symptoms disappeared after a course of nonsteroid anti-inflammatory drugs. One year later, the knee swelling reappeared; juvenile idiopathic arthritis was diagnosed and intra-articular steroid injection was performed. Due to persistence of arthritis of the knee he was admitted to our hospital. On physical examination variable skin-colored lesions were observed, which had been in existence for over 2 years. We performed a skin biopsy that showed an interstitial mucine deposition in the reticular dermis. Cutaneous Mucinosis of Infancy was diagnosed.
CONCLUSIONS: Cutaneous Mucinosis of Infancy is a persistent dermatosis with benign prognosis and no treatment is generally required. Our case report is particularly interesting because it is the first in which joint involvement has been reported in CMI, a disorder that has so far been described as limited to skin involvement. Further studies will be necessary in order to clarify the pathogenesis of joint involvement in primary mucinosis.