Acral papular mucinosisL98.5

Montgomery and Underwood, 1953; Rongioletti et al. 1986.

Rare (<50 cases reported in international literature), sporadic, papular mucinosis that is considered a topographically distinct, vatiante of localized lichen myxoedematosus. The disease is characterized by largely asymptomatic (only occasionally mild itching is reported), ivory to skin-colored, soft, 0.2-0.5 cm large, smooth-surfaced papules, especially on the backs of the hands and the extensor forearms.

Unknown;

Thyroid disorders, gammopathy, and lupus erythematosus are not expected in acral persistent papular mucinosis, as in all localized forms of lichen myxedematosus.

The coincidence with monoclonal gammopathy has been reported in a single case (Thatte SS et al.2015).

w:m=3:1; in a Japanese review study, the male-to-female ratio was reported to be 5:7 (Mori A et al. 2021). The mean age of affected individuals is approximately 40 years (14-77 years).

Distal forearms, backs of the hands, edges of the hands, extensor wrists

Single or multiple, usually disseminated, often symmetrically distributed, 0.2-0.4 cm in size, transparent to skin-colored or also white-yellowish or also brown-yellowish, little symptomatic papules, with a smooth surface. Occasional formation of smaller plaques due to confluence. See below Lichen myxoedematosus.

In larger reviews a malignancy frequency is stated (uterine carcinoma, mammary carcinoma, thyroid carcinoma). However, this statement needs further verification as it is not confirmed in other reviews (Luo DQ et al. 2011).

Unchanged epidermis; underneath broad, band-shaped, usually clearly delimited laterally and to the depth against the normal dermis, impressing in the HE preparation as a loosened collagen structure. There are no inflammatory infiltrates. Distally, there is again a normal collagen structure. Fibroblastic proliferation is variable but normally absent. In the Alcian blue staining the mucinous zone impresses by a distinct reactivity (see Fig.).

The differential diagnosis includes:

• Granuloma anulare: annular firm reddish surface smooth papules.
• Molluscum contagiosum: skin-colored bifurcated papules, eruptive appearance.
• Keratoelastoidosis marginalis of the hands: affects the lateral edges of the hands and fingers, small 0.1cm skin color, firm nodules
• Lichen amyloidosus: rarely on the forearms or hands. Concerns mainly the lower legs. Itching!
• Malignant atrophic papulosis (Köhlmeier-Degos disease): usually life-threatening systemic disease. Central spatter-like necrotic red papules. Often acute abdomen

Remark: Based on the localization of the lesions and the findings in histopathology (alcian blue staining), the diagnosis can be easily made.

The lesions of "acral persistent papular mucinosis" are limited to the skin; it is ultimately only a "cosmetic problem" with a good prognosis and without systemic involvement. Therefore, a wait-and-see approach may also be recommended (Rongioletti F 2006). S.a. Lichen myxoedematosus.

Topical and intralesional glucocorticoids have been used with variable success. However, this therapy is not recommended.

Individual papules can be removed electrocaustically or by ablative laser. Healing is generally without complications. Recurrences are possible.

A 31-year-old woman presented with a 10-year history of multiple, asymptomatic, symmetric, discrete papules on dorsum of hands and extensor forearms. The lesions started on the hands, slowly increased in size, and were persistent. They were not related to sun exposures. Apart from removal of a benign thyroid tumor six years earlier, there was no known history of other medical problems. The results of laboratory tests, including routine blood tests such as those of liver enzymes, renal function, thyroid profile, serum protein analysis, immunoglobulin levels, and autoantibody profile were o.b.. The patient denied previous trauma to the affected areas and recent contact with topical medications. No other family member was similarly affected (Luo DQ et al. 2011).

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