Self-healing infantile cutaneous mucinosis L98.5

Colomb D, Racouchot J, Vittoni F., 1973; < 30 cases have been published since the initial description in 1973 (Steffes WE et al. 2015).

Self-healing juvenile cutaneous mucinosis (SJCM) is a very rare, acute, benign and self-limiting disease characterized by the sudden appearance of asymptomatic papules and plaques. Febrile, even arthritic accompanying components are possible.

Self-healing juvenile cutaneous mucinosis (SHJCM) is, in addition to

• the classic papular mucinosis
• acral persistent papular mucinosis
• cutaneous infantile m ucinosis
• nodular mucinosis

one of 5 subtypes of localized papular mucinosis (see alsocutaneous mucinosis).

The etiopathogenesis of childhood cutaneous mucinosis is unclear. Normally, proteoglycans (mucin) are produced in only small amounts by dermal fibroblasts. It is postulated (as in other mucinoses as well) that the accumulation of mucin occurs through activation of dermal fibroblasts. The signal for increased formation of proteoglycans is possibly by autoantibodies, also by monoclonal or polyclonal immunoglobulins, by proinflammatory cytokines e.g. in viral infections, or also by a balance disturbance between production and degradation of mucins (Rongioletti F 2020). Since some cases with familial accumulation have also been described, a genetic factor is also discussed.

1-17 years, with some cases described in early adulthood (de las Heras ME et al 1996).

Preferably the trunk as well as the extremities are affected, more rarely also the capillitium, the face, the neck as well as the extremities.

In most cases, inconspicuous, asymptomatic, mostly skin-colored to slightly reddish, smooth papules and plaques, 0.2 to 3.0 cm in size, appear without prodromes. An acute, febrile onset with arthralgias, muscle pain, and generalized weakness has also been described. In another case, reddish nodules developed acutely on the trunk and extremities, along with periorbital edema, arthritis, and arthralgias. The changes may also simulate juvenile dermatomyositis (Bishnoi A et al. 2020). An 8-year-old child treated for nephroblastoma during chemotherapy developed acute cutaneous mucinous nodules characteristic of self-healing juvenile cutaneous mucinosis (Wadee S et al 1994).

Focal accumulation of alcian blue-positive proteoglycans in the upper dermis, usually clearly demarcated from the normal dermis. This results in a reticular pattern of cellular accumulation. Features of proliferative fasciitis may also be present, including a myxoid stroma and gangliocyte-like giant cells (Nagaraj LV et al 2006).

Although spontaneous complete regression of the lesions can be expected within a period of weeks to a few months, patients with SHJCM need long-term monitoring because of the possible development of dermato-rheumatologic diseases. The pathogenetic role of microbial pathogens should be further investigated (Luchsinger I et al. 2018).

Despite the rarity of this condition, it is important to keep SHJCM in mind as a differential diagnosis in pediatric patients who present with proliferating papules and nodules. Knowledge of this entity may prevent unnecessary diagnostic testing and aggressive treatment in the pediatric population with this self-limited disease.

A healthy 14-month-old girl suddenly developed asymptomatic, skin-colored to slightly reddish, firm "nodules" on the capillitium, face, hands, axillae, lower legs, and abdomen. A skin biopsy revealed a well-circumscribed collection of mucin in the reticular dermis. Colloidal iron staining was positive. Serum protein electrophoresis, thyroid function tests, complete blood count, erythrocyte sedimentation rate, and antinuclear antibodies were normal except for lymphocytosis. Most skin lesions had resolved within 6 months of onset. (Carder KR et al 2003).

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