Alopecia mucinosa

Alopecia mucinosa, often referred to as follicular mucinosis, was first reported by Pinkus in 1957.¹ The dermatologic eruptions consist of follicular papules and/or indurated plaques that demonstrate distinct histologic changes in the hair follicles that lead to hair loss. The accumulation of mucinous material in the damaged hair follicles and sebaceous glands creates an inflammatory condition and subsequent degenerative process. The face, the neck, and the scalp are the most frequently affected sites, although lesions may appear on any part of the body.

Pathophysiology

Alopecia mucinosa is a disease process defined histopathologically by mucin deposition in hair follicles and sebaceous glands, which undergo epithelial reticular degeneration. The exact pathogenesis is unknown, although the role of circulating immune complexes and cell-mediated immunity has been considered. The 3 clinical variants of the disease consist of a primary acute disorder of young persons, a primary chronic disorder of older persons, and a secondary disorder associated with benign or malignant disease.

The primary disorder of young persons consists of focal cutaneous lesions with limited progression. Lesions are typically limited to the head, the neck, and the shoulders (see the image below). Most lesions spontaneously resolve between 2 months and 2 years. Pediatric cases comprise most of this type of alopecia mucinosa, with the remainder of patients being younger than 40 years. Neonatal follicular mucinosis has also been reported

Primary chronic alopecia mucinosa of older persons affects people older than 40 years. Lesions have a widespread distribution, and they may persist or recur indefinitely. No associated disorders are identified.

The secondary alopecia mucinosa may be associated with either benign disease or malignant disease. These patients are usually aged 40-70 years, and the lesions are widespread and numerous. Alopecia mucinosa can occur secondary to benign disease including the inflammatory conditions lupus erythematosus, lichen simplex chronicus, and angiolymphoid hyperplasia. Secondary alopecia mucinosa is also associated with malignant disease, including mycosis fungoides, Kaposi sarcoma, and Hodgkin disease; mycosis fungoides is by far the most common association.^3,4,5
 
In most patients who exhibit both alopecia mucinosa and mycosis fungoides, these conditions appear to develop concomitantly; however, the concern exists that individuals exhibiting only alopecia mucinosa may also be at risk for subsequent development of lymphoma.

Drug-induced alopecia mucinosa has been associated with the use of adalimumab⁶ and imatinib

History

The presenting sign of alopecia mucinosa is hair loss in hair-bearing areas. Skin eruptions present as pruritic, pink–to–yellow-white, follicular papules and plaques. Lesions may be isolated or multiple. Mycosis fungoides is recognized at the time of diagnosis in approximately 15-30% of patients with alopecia mucinosa.

Physical

The clinical manifestations of alopecia mucinosa are grouped follicular papules and alopecia. Nodules, plaques, and patches of follicular papules may exist. Occasionally, mucinous material can be expressed from active lesions, and erythema and scaling are usually present. The face and the scalp are the most common sites of involvement.

Usually, the alopecia is reversible unless follicular destruction has occurred due to excess mucin in the outer root sheath and sebaceous glands. In patients with permanent alopecia, the whole follicle degenerates, and the cystic cavity becomes blocked with keratinous debris. When the plugs persist, they are obvious features on healed, hairless patches of alopecia mucinosa.

Causes

Alopecia mucinosa represents various stages of follicular damage leading to hair loss. The reactive process is of unknown etiology. The role of circulating immune complexes and cell-mediated immunity has been considered

Laboratory Studies

A history and physical examination are the first steps.

Procedures

Multiple skin biopsy samples are needed in the evaluation of patients with alopecia mucinosa because of the association with lymphoma.

Histologic Findings

The characteristic features of alopecia mucinosa are follicular degeneration with the accumulation of mucin within the follicles (see the image below). Early lesions contain an abundance of mucin between the decaying root sheath cells or pooling in localized collections. The mucinous degeneration begins in the pilosebaceous units. A periappendiceal, perivascular, or interstitial lymphocytic mixed inflammatory cell infiltrate often exists. In patients with chronic alopecia mucinosa, the histologic analysis demonstrates the presence of distorted follicles with variable viability.

Differentiation between the variants of alopecia mucinosa is difficult; thus, several criteria are used to differentiate the histologic features of benign alopecia mucinosa and mycosis fungoides–associated alopecia mucinosa.¹⁰ Although no single criterion is diagnostic,¹¹ cytologic atypia and a bandlike infiltrate are more common in mycosis fungoides. In addition, Pautrier microabscesses in the epidermis and upper follicle are rarely found in benign alopecia mucinosa but are common in mycosis fungoides. The benign inflammatory process is typically characterized by an infiltrate confined to the follicular, perifollicular, or perivascular zones with no extension of cells into the epidermis or papillary/reticular dermis. On the other hand, the typical infiltrate associated with mycosis fungoides involves the upper dermis invading the epidermis and includes characteristic tumor cells in the damaged follicle, epidermis, and/or dermis

Medical Care

No uniformly effective therapy exists for alopecia mucinosa, although several treatments are routinely used. Treatments include topical, intralesional, and systemic corticosteroids. In addition, topical and systemic psoralen plus ultraviolet A light (PUVA) therapy,¹² topical nitrogen mustard, and radiation therapy have demonstrated some success. Isolated cases document the beneficial responses of dapsone, indomethacin, and interferons.¹³ Because of the variable course of the disease and the likelihood of spontaneous resolution, therapeutic efficacy is difficult to prove

Complications

Although the question of whether alopecia mucinosa is a transitional state evolving into mycosis fungoides is unresolved, it is proven that alopecia mucinosa may precede the development of mycosis fungoides by several years. Thus, additional biopsy specimens and extremely close follow-up care are crucial in all variants of alopecia mucinosa.

Prognosis

The prognosis of alopecia mucinosa depends on the specific clinical variant, as follows:

• Primary acute disease usually disappears within 2 years; however, childhood alopecia mucinosa is not always self-limited and may possibly be related to Hodgkin disease.
• Primary chronic disease usually lingers for several years, but it can fluctuate in the extent of skin involvement at any given time.
• Secondary alopecia mucinosa has the least favorable prognosis when associated with coexistent malignancy.