Linear connective tissue naevus of the proteoglycan type ('naevus mucinosus')

Mucinous Nevus

Mucinous nevus is an uncommon entity classified as either a cutaneous mucinosis or a connective tissue nevus. The condition presents as grouped papules and coalescent plaques growing in a unilateral or zosteriform manner. The key histopathological feature is a band-like deposition of mucin in the superficial dermis. A 34-year-old male presented with grouped gray-brown papules and confluent plaques exhibiting a zosteriform distribution on the right side of the lower back. The lesions had commenced in childhood. Histological examination revealed mucin deposition in the papillary dermis. Thus, we diagnosed a mucinous nevus. To date, only a few reports of such nevi have been reported in the literature. Therefore we report a rare case of mucinous nevus.

[Mucinous nevus of late onset]

INTRODUCTION

Mucinous nevus is a rare disease characterized by mucin deposits in the dermis, with only 23 cases reported to date. It belongs to the connective tissue nevus family and is characterized by dermal mucin deposits. Two histological subtypes have been described: pure mucinous dermal nevus (connective tissue nevus of the proteoglycan [CTNP]) and combined mucinous nevus (combined CTNP) associating epidermal nevus with dermal mucin deposits. Lesions generally appear in childhood or early adulthood. We report herein the case of a 59-year-old man with a symptomatic lesion.

OBSERVATION

A 59-year-old man consulted for unilateral lesions occurring linearly along the Blaschko line on the right lower limb, composed of brown verrucous papules, which started at the age of 50. The patient complained of itching caused by friction from clothes. Histological examination of a papule highlighted an acanthotic epidermis, with elongation of rete ridges and mucin deposits in the dermis showing uptake of alcian blue stain. The clinicopathological analysis enabled diagnosis of combined CTNP. We treated this nevus by surgical dermabrasion and observed a slight and cosmetically acceptable scar.

DISCUSSION

To our knowledge, our patient is the oldest reported to date and the only one to have complained of symptoms. Our review of the literature highlights the importance of skin biopsy to guide aesthetic or symptomatic treatment. CO2 laser and dermabrasion are recommended for combined CTNP as they treat the epidermal component with low risk of secondary scarring. However, these techniques should be avoided in pure dermal CTNP, where surgical excision alone is acceptable in order to achieve optimal cosmetic results.

Mucinous nevus

A 15-year-old boy first noticed multiple firm papules on his right upper chest two years before presenting to our clinic. These papules were densely distributed and showed epidermal nevus-like linear arrangement at some sites. The number, size, and distribution of these papules remained unchanged for one year of our observation. The papules flattened leaving scars and did not recur within a year after one shaving abrasion using a scalpel. Histopathologically, epidermis of the papule displayed acanthosis with elongated rete ridges. Accumulation of mucin was apparent in the papillary and subpapillary dermis. In mucinous nevus, the origin of cells with nevoid proliferation is obscure. In contrast with common collagenous connective tissue nevus, it is hard to define the localized persistent mucin accumulation as a nevoid manifestation. The present case of mucinous nevus might be caused by significantly stimulated glycosaminoglycan synthesis in a kind of epidermal nevus without extreme hyperkeratosis.

A case of congenital mucinous nevus: a connective tissue nevus of the proteoglycan type

Mucinous nevus is a very rare entity and can be classified as both a cutaneous mucinosis (CM) and a connective tissue nevus (CTN). We describe the clinicopathologic features of an unusual case of mucinous nevus in a 14-year-old Korean boy who presented with zosteriform plaques of congenital onset.

Cutaneous mucinosis of infancy: is it a real entity or the paediatric form of lichen myxoedematosus (papular mucinosis)?

We describe a girl presenting with a childhood dermal mucinosis in which we had the unique opportunity to find all the transitional histological features of lichen myxoedematosus (papular mucinosis), from its early focal mucin deposition in the reticular dermis to its late findings of interstitial mucin deposition, dermal fibrosis and fibroblast proliferation. Her father reported having had similar lesions when he was a child, which completely disappeared during adolescence. This case, and a re-evaluation of the literature, suggests that cases of cutaneous mucinosis of infancy that are not hamartomatous conditions such as mucinous naevi are in fact the infantile presentation of lichen myxoedematosus (papular mucinosis) and, in addition to other cases in the literature, suggests a genetic and familial factor in lichen myxoedematosus (papular mucinosis).