Amyloidosis, Primary Localized Cutaneous, 3 (PLCA3)

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OMIM 57 617920 PS105250 MeSH 44 D028226 ICD10 via Orphanet 34 E85.4+ L99.0*

Orphanet 59 ORPHA319635 MedGen 42 C4554421 CN895592

UniProtKB/Swiss-Prot : ⁷⁴ Amyloidosis, primary localized cutaneous, 3: A primary amyloidosis characterized by localized cutaneous amyloid deposition. This condition usually presents with itching (especially on the lower legs) and visible changes of skin hyperpigmentation and thickening that may be exacerbated by chronic scratching and rubbing. Primary localized cutaneous amyloidosis is often divided into macular and lichen subtypes although many affected individuals often show both variants coexisting. Lichen amyloidosis characteristically presents as a pruritic eruption of grouped hyperkeratotic papules with a predilection for the shins, calves, ankles and dorsa of feet and thighs. Papules may coalesce to form hyperkeratotic plaques that can resemble lichen planus, lichen simplex or nodular prurigo. Macular amyloidosis is characterized by small pigmented macules that may merge to produce macular hyperpigmentation, sometimes with a reticulate or rippled pattern. In macular and lichen amyloidosis, amyloid is deposited in the papillary dermis in association with grouped colloid bodies, thought to represent degenerate basal keratinocytes. The amyloid deposits probably reflect a combination of degenerate keratin filaments, serum amyloid P component, and deposition of immunoglobulins. PLCA3 inheritance is autosomal recessive.

MalaCards based summary : Amyloidosis, Primary Localized Cutaneous, 3, also known as amyloidosis cutis dyschromica, is related to alveolar capillary dysplasia with misalignment of pulmonary veins and dyskeratosis congenita, autosomal dominant 6. An important gene associated with Amyloidosis, Primary Localized Cutaneous, 3 is GPNMB (Glycoprotein Nmb). Affiliated tissues include skin and neutrophil, and related phenotypes are pruritus and dry skin

OMIM : ⁵⁷ Amyloidosis cutis dyschromica (ACD), a rare form of primary localized cutaneous amyloidosis, is a pigmentary disorder in which keratinocyte-derived amyloid is deposited in the skin. Onset occurs before puberty and involves macular or reticulate hyperpigmentation admixed with symmetrically distributed guttate hypopigmented and hyperpigmented lesions. ACD can be distinguished from other conditions with similar clinical findings by a skin biopsy in which amyloid deposition in the papillary dermis is seen. Specific features that set ACD apart from the more common macular and lichenoid variants of primary cutaneous amyloidosis include dotted, reticular, or diffuse hyperpigmentation admixed with lentil-sized hypopigmented macules; mild or no associated pruritus; and, on histologic examination of skin from both hyper- and hypopigmented lesions, amyloid deposition confined to the papillary dermis, in close proximity to the epidermis (Huang et al. (2009); Mahon et al., 2016). For a discussion of genetic heterogeneity of primary localized cutaneous amyloidosis, see 105250. (617920)

Clinical features from OMIM:

617920

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