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The concept of follicular inflammation with associated intrafollicular mucin dates back to the early 20th century. Kreibich described the case of a 24-year-old man with plaques on the truncal area. The photograph illustrating the clinical and microscopic findings clearly shows the hair follicle to be enveloped by a lymphocytic infiltrate with abundant mucinous change in and adjacent to the follicle.3 The clinical resemblance to mycosis fungoides (MF) is striking, but there was no clear epidermal involvement with atypical lymphocytes to suggest a diagnosis of MF. Several years later, a similar case was described by Lehner and Szodoray. Once again, the process was reported in a young man, and the course was benign.4 For several years, Macauley followed a patient who first developed papules located over the eyebrow in association with hair loss. The microscopic picture was that of a primarily follicular-centered infiltrate with abundant intrafollicular mucinosis. After several years, the lesions resolved and hair growth resumed in the involved area. This patient became the index case in the series of seven cases reported by Pinkus as “alopecia

mucinosa.”1 Pinkus used this term to emphasize the clinical findings of hair loss and the microscopic changes of follicular mucinosis (FM). He emphasized the clinical picture of slowly evolving, asymptomatic, well-defined plaques. The mucin was reported to first become visible in the outer root sheath area and then the sebaceous gland and was shown to be hyaluronic acid. Eventually this process could result in destruction of the follicle. MF was not mentioned in this report as being part of the pathologic process of alopecia mucinosa. Later the same year, Braun-Falco reported four patients with a similar condition that he described as mucophanerosis follicularis et seboglandularis.2 The term “phanerosis” implied that the mucin became more visible in this condition, perhaps as a result of degeneration of the follicular structure. Two of these cases had MF associated with the follicular mucin changes. BraunFalco divided this condition into those cases that were symptomatic of MF (secondary to MF) and those that were primary or idiopathic. Jablonska et al. described another case and used the term “mucinosis follicularis” to describe the microscopic findings.5 Since these early descriptions, the terms “primary” or “secondary” FM have been used to separate those patients who have no clear evidence for MF from those who do have lymphoma. Emmerson separated the 47 cases in his report into three tiers, those with MF or malignancy, those with persistent disease but no lymphoma, and those with self-limited disease.6 Coskey and Mehregan described their experience with alopecia mucinosa in 50 patients. They reported a prevalence of MF in approximately 14%. It appeared up to that time that patients younger than 40 years of age and those with lesions limited to the facial area were not as likely to develop MF.7 Although FM in the strict sense is a histopathologic term, it has been used more often than the term alopecia mucinosa in recent years to describe this process of intrafollicular inflammation with mucin deposition. FM has been used perhaps incorrectly as a synonym for alopecia mucinosa.8 The precise terminology to best describe this disorder is still a matter of debate.