Chronic lesions [of alopecia mucinosa] are usually erythematous plaques with variable induration and scaling, but may also be gelatinous-appearing nodules and tumors. All such patients need evaluation for lymphoma, especially mycosis fungoides, since alopecia mucinosa may precede this disease. Shelley WB and Shelley D (eds.). In: Advanced Dermatologic Diagnosis, 1992.¹

Follicular mucinosis (alopecia mucinosa) presents as follicular papules, sometimes with associated erythema and scaling extending into follicular skin. Because mycosis fungoides is sometimes associated with this condition, a biopsy is essential . . . The clinical picture that is produced by the T-cell infiltrative disease known as follicular mucinosis is referred to as alopecia mucinosa . . . An attempt to asses the malignant potential of follicular mucinosis reveals the enigmatic nature of this and other cutaneous T-cell dyscrasias that are not clearly malignant. CTCL may be present before the development of alopecia mucinosa or may be diagnosed for the first time on the histologic examination of a biopsy specimen of alopecia mucinosa. There seems to be no reliable clinical finding for determining which patient with alopecia mucinosa will also have CTCL. Heald PW, Edelson RL. In: Dermatology in General Practice, 4th edition, 1993.²

Alopecia mucinosa. Once follicular mucinosis has been recognized in a biopsy, one has to decide whether the case is one of benign alopecia mucinosa or mycosis fungoides or other forms of T-cell lymphoma in which follicular mucinosis persists. The occasional transformation of the benign form into T-cell lymphoma has been well documented. Mehregan AH et al. In: Pinkus' Guide to Dermatohistopathology, 6th edition, 1995.³

Alopecia mucinosa (follicular mucinosis) . . . this condition is now classified into two types: a primary (idiopathic) type and a secondary (symptomatic) variety. When these types can be distinguished, the primary form, which may lead to permanent alopecia, tends to have a shorter but benign course. On the other hand, the secondary type is often associated with lymphomas of which the majority are of cutaneous T-cell type (mycosis fungoides), and this condition may evolve over many years, with a fatal outcome. Elder D et al. In: Lever's Histopathology of the Skin, 8th edition, 1997.⁴

Rarely, follicular mucinosis is also seen in plaques of mycosis fungoides. How does a histopathologist differentiate mycosis fungoides with that finding from alopecia mucinosa? By noting diagnostic findings of mycosis fungoides [in the epidermis especially] in the former and absence of them in the latter. . . . In short, mycosis fungoides is diagnosed on the basis of precise criteria specific for it, not by the presence or absence of follicular mucinosis. In contrast, the presence of follicular mucinosis is requisite for diagnosis of alopecia mucinosa. Ackerman AB, Chongchitnant N, Sanchez J, et al. Histologic Diagnosis of Inflammatory Skin Diseases, 2nd edition, 1997.⁵

Follicular mucinosis presents as two distinctly different clinical patterns of disease. The first, properly termed alopecia mucinosa, typically presents in childhood as a solitary or multiple erythematous plaques on the face, head or neck. The plaques are asymptomatic, tend to resolve spontaneously, and do not evolve into cutaneous T-cell lymphoma . . . The second pattern of follicular mucinosis consists of boggy nodules or plaques in patients with cutaneous T-cell lymphoma. Follicular mucinosis may herald the onset of cutaneous lymphoma. To avoid confusion, it is preferable to refer to the first pattern as alopecia mucinosa and to the second pattern as follicular mucinosis associated with cutaneous T-cell lymphoma. Maize JC et al. In: Cutaneous Pathology, 1998.⁶

Alopecia mucinosa most commonly involves the head and neck, but involvement of the trunk and extremities may occur. An associated lymphoproliferative disorder, most commonly mycosis fungoides, occurs in approximately 30 % of cases, especially in older patients with numerous lesions . . . Follicular mucinosis is considered by some to be a synonym of alopecia mucinosa, but this term is best used as a microscopic description of intrafollicular mucin deposits and not the clinical pathologic entity, alopecia mucinosa. Focal, limited follicular mucinosis outside of the setting of alopecia mucinosa occurs and likely represents a reactive follicular process. Whithing DA et al. In: Textbook of Dermatopathology, 1998.⁷

Follicular mucinosis. This condition affects predominantly face and head-neck region of middle-aged individuals. If terminal hairs of the beard or head are affected, a localized hair loss is noticed, hence alopecia mucinosa. It may occur as a group of individual follicular papules with prominent follicular openings or as large indurated plaque in which coalesced follicular papules are present. Follicular mucinosis of either variety may heal spontaneously after a few months to a few years, may have a chronic benign course, or may be associated with mycosis fungoides from the beginning or follow it. The chronic benign type may eventuate in mycosis fungoides. Hashimoto K, Barnhill RL. In: Textbook of Dermatopathology, 1998.⁸

Follicular mucinosis, the collection of acid mucopolysaccharides within the outer root sheath usually is accompanied by a lymphoid infiltrate, is commonly seen in mycosis fungoides. Rarely, it can procede the overt development of mycosis fungoides. Clinically, it is generally associated with patches of hair loss (alopecia mucinosa). Follicular mucinosis is also seen in a primary form unrelated to mycosis fungoides and in a variety of unrelated diseases. Sleater JP, Murphy GF. In: Pathology of the Skin, 2nd edition, 2000.⁹

Alopecia mucinosa and mycosis fungoides with follicular mucinosis have several histopatholoic features in common, namely, deposits of mucin in hair follicles and sebaceous lobules, lymphocytes within follicular and sebaceous epithelium, and an infiltrate that consists mostly of lymphocytes but sometimes is accompanied by eosinophils. The infiltrates in both conditions are superficial and deep, and perivascular and interstitial. Both diseases are accompanied with alopecia.

Follicular mucinosis is a distinctive pattern of epithelium, but it is not specific for any disease. It is the sine qua non, however for diagnosis of alopecia mucinosa. In contrast, follicular mucinosis is not seen commonly in mycosis fungoides and is not a criterion for diagnosis of that lymphoma . . .

Alopecia mucinosa is a specific inflammatory disease that begins as soft, skin-colored, or slightly red papules, arranged in clusters. Ackerman AB et al. Differential Diagnosis in Dermatopathology, 2001.¹⁰

The concept that follicular mucinosis is a tissue reaction pattern and not a disease sui generis is a relatively recent one and, as a consequence, most reports in the literature use the term 'follicular mucinosis' for what Pinkus described as alopecia mucinosa in 1957.

Follicular mucinosis (alopecia mucinosa) is an uncommon inflammatory dermatosis with a predilection for adults in the third and fourth decades of life. Three clinical types have traditionally been recognized: a benign transient form with one or several plaques or grouped follicular papules, usually limited to the face or scalp and with accompanying alopecia; a more widely distributed form with follicular papules, plaques and nodules on the extremities, face and trunk and a course often exceeding 2 years; and a third group, accounting for 15–30 % of cases with widespread lesions and associated with malignant lymphoma of the skin or mycosis fungoides. Weedon D. Skin Pathology, 2nd edition, 2002.¹¹

[Alopecia mucinosa] is a rare inflammatory skin disease that occurs predominantly in young adults, both male and female, and is characterized by grouped follicular papules and plaques, most commonly on the face and the scalp but also occasionally affecting other sites of the body. [. . .] Apart from an idiopathic manifestation that heals within weeks or months there is a chronic one which persists over years and affects commonly sites other than the scalp. [. . .] The most important differential diagnosis is follicular mucinosis in association with malignant T-cell lymphomas. Follicular mucinosis may also manifest itself clinically as circular alopecic lesions and, therefore, is a differential diagnosis clinically as well. Histologically, follicular mucinosis can be distinguished with surety from alopecia mucinosa because, as a rule, only a part of all follicles in a biopsy is affected. (translated from the German). Meigel WN and Stemm A. In Histopathologie der Haut, 2003.¹²