Indian Journal of Dermatology
: 2007  |  Volume : 52  |  Issue : 1  |  Page : 64--65

Mucinous naevus: An unusual presentation

Rashmi Kumari, Devinder Mohan Thappa, S Jayanthi 
 Department of Dermatology and STD, JIPMER, Pondicherry - 605 006, India

Correspondence Address:
Devinder Mohan Thappa
Department of Dermatology and STD, JIPMER, Pondicherry - 605 006

How to cite this article:
Kumari R, Thappa DM, Jayanthi S. Mucinous naevus: An unusual presentation.Indian J Dermatol 2007;52:64-65

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Kumari R, Thappa DM, Jayanthi S. Mucinous naevus: An unusual presentation. Indian J Dermatol [serial online] 2007 [cited 2021 Jun 13 ];52:64-65
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A 23-year-old man presented with multiple firm papules over his chest extending onto both his shoulders since childhood. There was no significant personal or family history. On examination, multiple, discrete, firm follicular as well as non-follicular shiny papules were seen mainly over the anterior chest and extending onto both the shoulders [Figure 1]. Underlying skin was not thickened or hide bound. Also seen was a 4 cm horizontal keloid over the sternum. No other physical or systemic abnormality was detected. Routine laboratory investigations were normal and there was no evidence of paraproteinemia.

On histopathological examination of representative papule, epidermis was acanthotic with thin, elongated rete ridges and mild hyperkeratosis. In the papillary dermis, mucin deposition was seen around a hair follicle without any fibroblastic proliferation [Figure 2]. On special staining, mucin deposition was seen in the papillary dermis.

Mucinous naevus was first described by Redondo Bellon et al[1] in 1993, who demonstrated a congenital plaque like lesion in the interscapular area in a 16-year-old female very similar to that seen in our case over the chest. The term mucinous naevus was proposed because of its naevoid appearance and characteristic pattern of mucin deposits in the papillary dermis.

Cutaneous mucinosis (CM) can be divided into two groups: distinctive (primary) CM in which the mucin deposition is the main histologic feature, resulting in clinically distinctive lesions; and secondary cutaneous mucinosis, in which histologic mucin deposition is only an additional histological feature. The primary CM are sub-grouped into degenerative-inflammatory (diffuse) and neoplastic-hamartomatous (focal) mucinoses.[2]

Mucinous naevus is recently thought to be a variant of either connective tissue naevus of proteoglycan type or primary distinctive cutaneous mucinosis of the hamartomatous/ focal type.[3] The lesions usually develop at birth[1] or in early adulthood[4],[5] and the lower part of the trunk is the most commonly affected site. Brakman et al and Rongioletti and Rebora reported two adult cases of linear mucinous nevus on the back, showing a zosteriform pattern.[4],[5]

The histopathology in all cases designated as mucinous nevus includes a papillary dermal mucin deposit with or without elongated rete ridges in a band like fashion. The origin of the mucin deposited in the lesion remains unclear, but it seems to be the result of a primary metabolic process (overproduction) rather than of a secondary catabolic process.[6] This idea is supported by the fact that in all reported cases the lesions developed early in life, even at birth, without evidence of trauma or a pre-existing pathological change at the site of the lesions.

There are, to our knowledge, six cases identified as mucinous nevus in the English language literature,[6],[7],[8],[9],[10] although some cases of cutaneous mucinosis of infancy (CMI) reported earlier might be identical to mucinous nevus[1] and hence were considered a differential diagnosis in our case.

Cutaneous mucinosis of infancy (CMI) is a rare condition that is categorized as a degenerative-inflammatory mucinosis (diffuse). The lesions of CMI are either symmetrical or grouped small papules of congenital or infantile onset on the upper extremities or the trunk.[10],[11] Histology shows a focal, well-circumscribed deposit of mucin in the papillary dermis without fibroblast proliferation.[3] The lesions tend to be progressive unlike mucinous nevus. Another differential diagnosis is cutaneous focal mucinosis, is a solitary papule or nodule with a marked proliferation of mucoblasts, eventually replacing most of the collagen.[3]

This case is being reported for its rarity. Naevus with such widespread involvement over the anterior chest and shoulders has not been previously described. The mucin deposition in the papillary dermis surrounding a hair follicle was confirmative of the diagnosis.


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