Follicular mucinosis L98.5

Kreibich, 1926; Pinkus, 1957

Nonspecific follicular reaction in the case of adnexotropic inflammatory or tumorous (especially in cutaneous T-cell lymphomas) infiltration of the corium with follicular papule formation, erythema and alopecia; detection of intraepithelial "mucin accumulations" in degenerated sebaceous gland and follicular epithelial cells.

4 clinically (but not histologically) distinct disease patterns can be distinguished:

• Type I (most common): Acute or subacute localized course associated with circumskripterous alopecia of the terminal hairs in children and young adults. Few 2.0-3.0-4.0 cm, nummular alopecia with skin-colored follicular papules.
• Type II (less common): Chronic, often generalized course in middle-aged to older adults, with disseminated, 0.1 cm, skin-colored, sometimes red follicular papules on the trunk and extremities. May be associated with pruritus.
• Type III (rare) Symptomatic form: Chronic, usually generalized course in middle-aged to older adults (very rarely in children and adolescents), with disseminated, skin-colored or red, 0.1 cm, usually pruritic, follicular papules on the trunk and extremities (rarely face). Considered a precursor stage of follicular cutaneous T-cell lymphoma (see mycosis fungoides folliculotrope below).
• Type IV (rare) Follicular mucinous nevus: A circumscritical form of mucinosis follicularis may also appear as a "follicular mucinous nevus" (note: not to be confused with nevus mucinosus a mucinous connective tissue nevus).

Unknown, idiopathic and symptomatic forms.

In some cases (type III) mucinosis follicularis is considered to be a (non-specific) precursor stage of a (follicular) cutaneous T-cell lymphoma ( = follicular mycosis fungoides) (see also Mycosis fungoides, follikulotropic).

Children and teenagers, adults (20-30 y/ 50-60 y).

Type I: Face and and capillitium

Type II: Mainly trunk and proximal extremities (face rarely affected)

Type III: Mainly trunk and proximal extremities (face rarely affected)

Herd-shaped, grouped, follicular, well-defined, flatly raised, infiltrated, reddened, asymptomatic or clearly itchy (especially in the forms occurring in older adults, which are almost always the expression of an adnexotropic cutaneous T-cell lymphoma) solid papules with firmly adhering scaling or follicular hyperkeratosis. Diffuse forms of distribution are rarer. Clinical picture of a "grater skin". The hair loss occurring in the affected areas (also Alopecia mucinosa) is reversible in children, but irreversible in the case of adnexotropic T-cell lymphomas.

Vacuolar epithelial cell degeneration with formation of optically empty or also basophilic clefts and cavities containing granular material in the outer root sheath of the hair follicle or the supraseboglandular part of the follicle (also in the sebaceous gland lobules). Mostly distinct follicular keratosis. Always evidence of a mostly sparse, but focally condensed perifollicular lymphoid infiltrate with focal epitheliotropy. In PCR, usually only in repeated approaches, detection of a monoclonal rearrangement of the gamma T cell receptor.

Pattern: Folliculitis infundibular and bulbar, spongiotic .

Clinical and histological:

• Alopecia areata: Important differential diagnosis; no itching; follicular papules in alopecia areata very discreet; only visible with lateral illumination. Histologically no evidence of "mucinous follicular degeneration".
• Naevus mucinosus: Congenital or less frequently acquired, in unilateral linear (naevoid) arrangement. Histology identical with mucinosis follicularis.
• Mycosis fungoides, follikulotrope: Probably not a "true" DD, because many authors consider (detectable) follikulotrope MF as a late stage of mucinosis follicularis (type II).
• Urticaria-like mucinosis follicularis. Very rare (entity doubtful), especially in middle-aged men, head and neck, urticarial follicular papules and plaques with interspersed follicular papules.
• Tinea corporis: Short course; clearly marginalized foci, follicular papules not evenly distributed over the affected area; histological and/or cultural evidence of fungus.
• Tinea barbae: see above
• seborrheic eczema: important DD; typically located in the seborrheic zones; no alopecia; histologically no mucin deposits.
• Keratosis follicularis: type rusticanus; extensor extremities; onset already in childhood or adolescence. Clinical signs of keratosis pilaris syndrome (keratosis follicularis ulerythema ophryogenes, folliculitis ulerythematosa reticulata, folliculitis decalvans).
• Lichen simplex chronicus: Only few foci, firm, mostly scratched papules, often confluent to plaques; very localized; histologically "eczema picture"; no mucin deposits.
• Lichen planus follicularis: Mostly localized at the capillitium; pinhead-sized, follicular, soft to strong red colored erythema (papules) arranged like a ruff around the hair follicle; older burnt areas show an atrophic scarred, smooth reflecting surface without erythema or follicular structures. Histological clarification necessary. Histological signs of interface dermatitis.

• Idiopathic form: In smaller flocks, especially with head infestation, experiment with glucocorticoids externally such as 0.1% betamethasone lotio (e.g. Betagalen Lotio, R030 ) or 0.1% triamcinolone cream (e.g. Triamgalen, R259 ) Possibility of therapy also with Tacrolimus/Pimecrolimus possible. In case of therapy failure or severe manifestation /TypeII/Type III) systemic glucocorticoids like prednisone (e.g. Decortin) 40-60 mg/day p.o. with slow reduction.
• Clinical types II and III can be tested individually or in combination with glucocorticoids DADPS (e.g. Dapson-Fatol) 100 mg/day p.o., PUVA therapy or SUP.
• Treatment successes with interferons are described. The disease shows a spontaneous regression tendency, which makes it difficult to assess the ultimate treatment success of the methods mentioned.
• The X-rays used in the past are today completely replaced by the above mentioned therapy methods.
• Symptomatic form: Treatment of the underlying disease, possibly supportive as above.

• Idiopathic mucinosis follicularis:
  • Acute course with spontaneous healing after weeks to months without permanent alopecia.
  • Chronic form (?): Extension over the entire integument is possible.
• Symptomatic mucinosis follicularis (early form of a folliculotropic mycosis fungoides): Persistence over several years, transition to a clinically and histologically confirmed follicular mycosis fungoides.

Follicular, perifollicular and sweat gland-associated mucinous processes are increasingly observed in HIV-infected persons and may be attributed to a tendency to "mucinous degenerative reactions" in this clientele (described as eccrine mucinosis, perifollicular mucinosis). Eccrine mucinosis is also observed in folliculotropic T-cell lymphomas.

1. Brown HA et al (2002) Primary follicular mucinosis: long-term follow-up of patients younger than 40 years with and without clonal T-cell receptor gene rearrangement. J Am Acad Dermatol 47: 856-862
2. Buchner SA et al (1991) Follicular mucinosis associated with Mycosis fungoides. Dermatologica 183: 66-67

3. Daudén E et al (2000) Eccrine ductal mucinosis in ahuman
   immunodeficiency virus-positive patient with probable scabies. Br JDermatol
   143:1335-1336

4. Demirkesen C et al (2014) The clinical features and histopathologic patterns of folliculotropic mycosis fungoides in a series of 38 cases. J Cutan Pathol doi: 10.1111/cup.12423
5. Garrido MC et al (2013) Primary cutaneous follicle center lymphoma with follicular mucinosis. JAMA Dermatol 150:906-907
6. Hagedorn M et al (1986) Treatment of a symptomatic mucinosis follicularis in mycosis fungoides with fast electrons. Dermatologist 37: 667-672
7. Kluk J et al (2013) Follicular mucinosis treated with topical 0.1% tacrolimus ointment. Clin Exp Dermatol 39: 227-228
8. Muscardin LM et al (2003) Acneiform follicular mucinosis of the head and neck region. Eur J Dermatol 13: 199-202
9. Oiso N et al (2014) Follicular mucinous nevus: a possible new variant of mucinous nevus. J Am Acad Dermatol 71 doi: 10.1016/j.jaad.2014.04.065
10. Pinkus H (1957) Centennial Paper. Alopecia mucinosa. Inflammatory plaques with alopecia characterized by root-sheath mucinosis. Arch Dermatol 76: 419-426