Follicular Mucinosis

Follicular mucinosis (also known as alopecia mucinosa) is a rare cutaneous disease characterized by the accumulation and deposition of mucin in hair follicles and sebaceous glands, with follicular keratinocytes being the presumable origin of excessive mucin [1] [2] [3] [4]. The pathogenesis of follicular mucinosis is yet to be revealed, and the clinical presentation varies only slightly across different subtypes that have been described in the literature [1] [4] [5] [6] [7]

• Idiopathic (primary or benign) - In the absence of an underlying etiology that could be responsible for cutaneous symptoms, primary or idiopathic follicular mucinosis is predominantly encountered in children and young adults as solitary lesions in the form of erythematous plaques or nodules accompanied by alopecia on the head and neck area, including the face [2] [3] [7]. Plaques are well-demarcated, skin-colored or pink, show signs of scaling and spontaneously resolve within a period of months or years [2] [4] [7]. In some patients, a prolonged and more chronic course of the disease has been reported, distinguished by several relapses and dissemination of lesions on the trunk and the extremities [3].
• Secondary - The presence of generalized erythematous plaques and alopecia is almost universally associated with some underlying disorder [2] [3] [7], and patients are much older compared to primary forms (40-70 years of age) [4]. Mycosis fungoides and Sézary syndrome (cutaneous T-cell lymphomas) are two most important pathologies linked to follicular mucinosis; systemic lupus erythematosus (SLE), various dermatoses (eczema, alopecia areata, insect bites, etc.) have all been recognized in secondary forms of this cutaneous disorder [1] [3] [5] [7].

Because of the wide differential diagnosis that may be seen with follicular mucinosis, particularly in older adults, the physician must conduct a thorough clinical investigation. Firstly, the course of symptoms, their severity, as well as their progression or possible relapse should be assessed. It must be noted that some of the underlying etiologies (eg. mycosis fungoides) might develop before, after, or together with follicular mucinosis, which is why a detailed personal history is essential in revealing disease that can point to the causative illness [1] [7]. A meticulous inspection of the skin that will allow detection of typical erythematous plaques and alopecia is perhaps even more important in narrowing the number of possible diagnoses. To confirm follicular mucinosis, however, a biopsy of the lesion and subsequent histopathological examination is necessary [1] [3] [4]. Confirmation of mucin deposition in the external root of the hair follicle and sebaceous glands and an abundant lymphocytic infiltrate in the follicles are main microscopic findings [1] [7]. Many studies have attempted to find histological criteria that could differentiate between idiopathic and secondary forms of follicular mucinosis, but the appearance of both subtypes on histology is virtually identical [2] [5]. Thus, the classification rests on clinical criteria and the ability of the physician to recognize main clinical features.

1. Passos PCV da R, Zuchi MF, Fabre AB, Martins LEAM. Follicular mucinosis - Case report . An Bras Dermatol. 2014;89(2):337-339.
2. Lewars M, Levin J, Purcell S. Follicular mucinosis. Indian Dermatol Online J.. 2013;4(4):333-335.
3. Fonseca APM, Campelo FS, Bona AH, Rêgo PMM, Fonseca WSM. Follicular mucinosis: literature review and case report. An Bras Dermatol. 2002;77:701–706.
4. Westphal DC, Pennini SN, de Souza PP, Maquiné GÁ, Schettini APM, Santos M. Follicular mucinosis: an important differential diagnosis of leprosy in an endemic area. An Bras Dermatol. 2015;90(3 Suppl 1):147-149.
5. Rongioletti F, De Lucchi S, Meyes D, et al. Follicular mucinosis: a clinico pathologic, histochemical, immunohistochemical and molecular study comparing the primary benign form and the mycosis fungoides - associated follicular mucinosis. J Cutan Pathol. 2010;37:15–19.
6. O'Reilly K, Brauer J, Loyd A, Patel R, Walters R, Franks AG Jr. Secondary follicular mucinosis associated with systemic lupus erythematosus. Dermatol Online J. 2010;16(11):7.
7. Rupnik H, Podrumac B, Zgavec B, Lunder T. Follicular mucinosis in a teenage girl. Acta Dermatovenerol Alp Pannonica Adriat. 2005;14(3):111-114.