Alopecia Mucinosa

Alopecia mucinosa (follicular mucinosis) is an inflammatory disorder with accumulation of mucin in the hair follicles and sebaceous glands, which causes patches of hair loss and follicular plaques.

There are two main forms.

The primary, idiopathic form affects children and young adults, mainly on the head and neck, with single or few lesions that often resolve in 2 months to 2 years.

The secondary form occurs with mycosis fungoides or other lymphoma, mainly in older adults (over 40 years), with multiple, extensive lesions, and in a few with inflammatory disease.

It is uncommon. Some experts doubt that the benign and malignant forms can be distinguished from clinical features alone.

Pathophysiology.

Mucin (hyaluronic acid) accumulates in the outer root sheath and sebaceous glands, apparently from an inflammatory cell infiltrate stimulating production. In lymphoma associated disease, malignant T cells are present in the infiltrate.

• Erythematous, scaly, indurated plaques or grouped follicular papules, mostly on the face, scalp and neck, which are alopecic with loss of hair and eyebrows.
• Primary form: single or a few plaques, often mildly itchy.
• Secondary form: widespread, with scale and infiltration, and sometimes tumour nodules and signs of mycosis fungoides.

Red flags.

• Age over 40 years, widespread or persistent disease, severe itch, or lymph node enlargement.
• Atypical lymphocytes or clonal T cells on biopsy.

• Biopsy (4 mm punch, deep enough to include follicles): mucin in the follicular epithelium and sebaceous glands (Alcian blue or colloidal iron stains), with a perifollicular lymphocytic infiltrate.
• T-cell receptor gene rearrangement and immunophenotyping to look for clonality, which is not by itself diagnostic.
• If lymphoma is suspected: full blood count with film and flow cytometry for Sezary cells, lactate dehydrogenase, lymph node examination and imaging for extensive or atypical disease.

Differential diagnosis.

• Alopecia areata, tinea capitis and discoid lupus erythematosus.
• Mycosis fungoides (folliculotropic type), seborrhoeic dermatitis and atopic dermatitis.
• Lichen planopilaris and secondary syphilis.

• Primary, localised disease: potent topical corticosteroid (clobetasol 0.05% daily for 6 weeks, then rest), intralesional triamcinolone 10 mg/mL monthly, or tacrolimus 0.1% twice daily. Many lesions resolve in 2 months to 2 years.
• Extensive or resistant primary disease: hydroxychloroquine 200 mg twice daily, minocycline 100 mg twice daily, dapsone 50 to 100 mg daily, or isotretinoin. Narrowband ultraviolet B and PUVA are alternatives.
• Disease linked to mycosis fungoides: skin directed therapy (topical mechlorethamine or carmustine, phototherapy with PUVA, local radiotherapy) and systemic therapy (bexarotene, interferon alfa, methotrexate or chemotherapy) by a cutaneous lymphoma team.
• Reassure patients with primary disease, but advise long term review.

Special groups. Pregnancy: avoid isotretinoin and PUVA, and use dapsone only with specialist advice.

Monitoring. Review every 3 to 6 months for 5 years in all adults, and yearly afterwards, with repeat biopsy for new or changing lesions.

Referral and escalation. Dermatology; cutaneous lymphoma service for atypical histology, clonality with progression or age over 40 years.