Diagnosis: Acral persistent papular mucinosis (APPM). Microscopic findings Hematoxylin-eosin–stained sections showed a papule containing a poorly circumscribed collection of widely separated collagen bundles in the upper dermis. Colloidal iron staining (Figure 4) confirmed the presence of an extensive dermal mucin deposition, which had produced the lesion. Figure 4. View LargeDownload Discussion Acral persistent papular mucinosis, which was first described in 1986 by Rongioletti et al,1 is 1 of 5 subtypes of the localized papular form of lichen myxedematosus that were described in Rongioletti and Rebora's2 recently updated classification of papular mucinosis, lichen myxedematosus, and scleromyxedema. It is rare, with only 17 cases reported to date. The female-male ratio is 4.7:1. Patients present with multiple, asymptomatic, noncoalescing, skin-colored papules that are limited in distribution to the extensor surfaces of the hands and wrists. There may be some extension to the forearms, but the trunk and the proximal aspect of the extremities are not involved. Sclerotic features are absent. The pathogenesis of APPM is unknown, and its course is characterized by either no change or an indolent progressive increase in the number and distribution of papules. Spontaneous remission generally does not occur. According to the updated classification proposed by Rongioletti and Rebora,2 there are no associated paraproteinemias, thyroid disease, or other systemic manifestations. However, an earlier case of APPM associated with IgA monoclonal gammopathy has been reported.3 The benign clinical course of APPM has produced few data on therapeutic options. Crovato et al4 reported no response to topical corticosteroid therapy, whereas Borradori et al3 reported resolution with topical application of 0.05% clobetasol propionate once daily for several weeks. In the latter report, however, there was a gradual return of the lesions after treatment with the topical steroid was discontinued. Histologically, hematoxylin-eosin staining demonstrates a papule formed by mucin deposition that produces widening of the spaces between collagen fibers in the middle to upper reticular dermis. Staining with colloidal iron or alcian blue (positive at a pH of 2.5; negative at a pH of 0.5) highlights the hyaluronic acid in the reticular dermis, generally with sparing of a subepidermal zone. Fibrosis and proliferation of fibroblasts do not occur to the same degree in APPM as in papular mucinosis. A further point of distinction from the latter condition is localization of mucin to the upper and middle dermis rather than widespread dermal deposition.5 References 1. Rongioletti FRebora ACrovato F Acral persistent papular mucinosis: a new entity Arch Dermatol. 1986;1221237- 1239http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&Dopt=r&uid=entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3777968&dopt=AbstractGoogle ScholarCrossref 2. Rongioletti FRebora A Updated classification of papular mucinosis, lichen myxedematosus, and scleromyxedema J Am Acad Dermatol. 2001;44273- 281http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&Dopt=r&uid=entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11174386&dopt=AbstractGoogle ScholarCrossref 3. Borradori LAractingi SBlanc FVerola ODubertret L Acral persistent papular mucinosis and IgA monoclonal gammopathy: report of a case Dermatology. 1992;185134- 136http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&Dopt=r&uid=entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1421626&dopt=AbstractGoogle ScholarCrossref 4. Crovato FNazzari GDesairello G Acral persistent papular mucinosis J Am Acad Dermatol. 1990;23121- 123http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&Dopt=r&uid=entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2365861&dopt=AbstractGoogle ScholarCrossref 5. Weedon D Skin Pathology London, England Harcourt Publishers Ltd1998;