Pathology of Follicular Mucinosis (Alopecia Mucinosa)
7 Facts About Pathology of Follicular Mucinosis
Alopecia mucinosa is a clinicopathological entity which presents with several erythematous papules and plaques mainly over the head and face regions with associated loss of hair and histopathological findings of follicular mucinosis characterized by the accumulation of mucin in the follicular epithelium and sebaceous glands.
It was described for the first time by Pinkus et al., in 1957, who named it mucinous alopecia.
Jablonska et al. named it follicular mucinosis, in 1959.
3) Clinical presentation:
Patients most commonly present with well-delimited, erythematous or brownish-erythematous papules and indurated plaques together with hair loss.
4) Clinical subtypes:
Classically, three forms are described:
i) Primary ( idiopathic) of short evolution in children and young adults :
Primary follicular mucinosis of short evolution occurs in children and young adults, presenting few lesions. It is limited to the head and neck regions. Lesions may remit spontaneously after 2 to 24 months, with no relapses.
ii) Primary (idiopathic) of prolonged course in older patients :
Primary follicular mucinosis of prolonged course occurs in older patients, manifesting itself with multiple lesions of chronic course. These lesions are prone to relapses.
iii) Secondary follicular mucinosis:
This form is associated with diverse benign or malignant conditions. It usually appears between the fourth and seventh decades of life, with multiple infiltrated plaques, which are commonly associated with systemic diseases, particularly lymphoproliferative malignancies.
Unfortunately, no clinical or histopathological pattern is predictive of its course or can reliably differentiate the two entities. Many have proposed criteria to differentiate primary follicular mucinosis from secondary follicular mucinosis with considerable difficulty.
5) Diseases associated with secondary follicular mucinosis :
Secondary follicular mucinosis may be associated with benign diseases (lupus erythematosus, insect bites, eczema, alopecia areata, hypertrophic lichen planus) or malignant (mycosis fungoides and Sezary syndrome, leukemia cutis, cutaneous B-cell lymphoma, Hodgkin's disease and anaplastic large cell lymphoma). A case of follicular mucinosis associated with metastatic clear cell renal cell carcinoma has also been reported.
"Cerroni et al. analyzed the clinicopathological features of 44 cases of follicular mucinosis . In their series, 16 cases were idiopathic primary follicular mucinosis, and the remaining 28 cases were lymphoma-associated. Twenty-six of 28 cases were mycosis fungoides, and the remaining 2 cases were Sézary syndrome. They claimed that follicular mucinosis might represent a form of localized cutaneous T-cell lymphoma."
Ishida M, Iwai M, Yoshida K, Kagotani A, Okabe H. Adult T-cell leukemia/lymphoma accompanying follicular mucinosis: a case report with review of the literature. International Journal of Clinical and Experimental Pathology. 2013;6(12):3014-3018.
The follicular keratinocytes have been considered to be the source of mucin. The exact pathogenesis is unknown, although the role of circulating immune complexes and cell-mediated immunity has been considered including a reaction to persistent antigens such as Staphylococcus aureus.
7) Microscopic features:
The lesion is characterized by mucin deposition within the follicular epithelium with a superficial and deep perivascular and interstitial mixed-cell infiltrate. There is follicular, perifollicular and perivascular inflammatory cellular infiltrate.
Follicles may show cystic cavities containing mucin, keratinous material and inflammatory cells.
The mucinous material is stained by the alcian blue and colloidal iron methods.
Westphal DC, Pennini SN, de Souza PP, Maquiné GÁ, Schettini APM, Santos M. Follicular mucinosis: an important differential diagnosis of leprosy in an endemic area. Anais Brasileiros de Dermatologia. 2015;90(3 Suppl 1):147-149.
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