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Fibrosing alopecia in a pattern distribution introduction
Several methods have been adopted with respect to the classification
system for primary scarring alopecia. Some classifications are
based on the age of onset, some based on clinical features,
and yet others
on pathology. Nevertheless, the most popular and accepted classification
of primary cicatricial alopecia is the one defined by the North
American Hair Research Society (NAHRS). This classification
is based on principal inflammatory cell type, (“lymphocytic” or “neutrophilic”),
as observed in scalp biopsy specimens taken from active lesions.
Cicatricial alopecia is very often a diagnostic dilemma. Scientists
and clinicians all over the world play a pro-active role in
research studying stem cell depletion, enzymatic defects,
abnormal immune
responses, abnormal follicular structures, defective hair
follicle recycling, genetic abnormalities and the like in scarring
alopecia.
Documentation of such research offers dermatologists a practical
approach to diagnosis, insight to the possible mechanisms
of various forms of alopecia, as well as therapeutic updates.
One such research study conducted and documented by Martin
S. Zinkernagel and Ralph M. Trüeb describes a distinctive form of scarring
hair loss. The clinical and histological findings in 15 women and
4 men with a distinctive form of progressive scarring alopecia in
a pattern distribution as studied and described by these doctors
has led to the conjecture that this could be a “new” form
of scarring alopecia not described before.
All 19 patients under observation had clinical and histological
features suggestive of Androgenetic alopecia, but with
additional features commonly seen in inflammatory scarring alopecia.
Androgenetic alopecia (AGA) is the most common cause of
balding, typically
presenting as loss of hair over the vertex (top) of the
scalp in affected people.
The term androgenetic alopecia denotes that both a genetic
predisposition and the presence of androgen activity are
necessary to cause
expression. Though androgenetic alopecia is caused by
androgen
hormone activity
in the hair follicles, hair loss in most affected individuals
is associated with normal levels of estrogens and androgens
in both
men and women.
In addition to the androgenetic alopecia hair loss pattern,
the patients under study by Drs Zinkernagel and Trüeb also had
additional features of an inflammatory scarring alopecia. The scarring
was confined to the same zone of hair loss seen with common balding,
and presented as perifollicular erythema (redness), loss of follicular
ostia (hair follicle openings) and follicular Keratosis (hardening).
Heavy, chronic inflammation was found around the upper portion of
the hair follicles in all the patients. The majority of the patients
displayed concentric perifollicular fibrosis (scarring). Focal degeneration
of the follicular basal layer was reported, which means that there
was degeneration of the cells that normally undergo rapid cell division
to produce hair fiber and to a lesser extent replenish the regular
loss of skin by shedding from the surface. This was combined with
apoptosis of follicular keratinocytes in some of the cases. (Apoptosis
is a physiological form of cell death that is responsible for the
deletion of cells and typically occurs concurrently in disorders
in which basal cell damage occurs).
The results were evaluated and compared with other diseases
that feature scarring of the central scalp area, specifically,
lichen
planopilaris, pseudopelade, and follicular degeneration
syndrome. It was observed that the patients developed
progressive fibrosing
alopecia of the central scalp, without the localized
areas of involvement typical of lichen planopilaris
and pseudopelade.
Perifollicular erythema, follicular keratosis, and
loss of follicular
orifices
or openings were limited to a patterned area of involvement.
The specific type of lichenoid inflammation selectively
was directed
at the miniaturizing hairs (smaller in diameter and
length) seen in common balding.
The authors supplied evidence that their patients
had both androgenetic alopecia and a form of inflammatory
scarring
alopecia. It was
then concluded that some patients with androgenetic
alopecia might have
additional clinical and histological features of
inflammation and fibrosis limited to the area of androgenetic
hair
loss. In these
patients, the histological findings of early lesions
are identical to those seen in lichen planopilaris.
The lichenoid
tissue
reaction, characterized by keratinocyte enlargement,
leads to follicular
destruction in these patients, and may be pathogenetically
related to the events
underlying androgenetic alopecia.
With the documentation by Zinkernagel and Trueb
of the above case study, it is still to be determined
whether
the condition
described
above is a patterned Lichen Planopilaris or is
androgenetic alopecia with a lichenoid tissue reaction pattern.
To put it simply, lichenoid
tissue reactions are characterized by epidermal
basal
cell damage.
Fibrosing alopecia in a pattern distribution clinical features
Biopsy specimens of early lesions demonstrated hair follicle miniaturization
and a lichenoid inflammatory infiltrate targeting the upper follicle
region of the miniaturizing hair folicles. Advanced lesions under
the microscope showed perifollicular lamellar fibrosis (growth of
excessive amounts of fibrous tissue) and completely fibrosed follicular
tracts, identical to end-stage lichen planopilaris, pseudopelade,
or follicular degeneration syndrome.
Differential Diagnosis
The inflammation in Fibrosing alopecia in a pattern distribution
(FAPD) seems to target the small-miniaturizing follicles, a finding
that has not as yet been noted in lichen planopilaris. But then
again, this may be because no one else has as yet looked for this
particular finding.
Fibrosing alopecia in a pattern distribution shares similar clinical
features with Central centrifugal cicatricial alopecia, especially
the manner in which the hair loss is centered on the crown and vertex,
and lamellar fibroplasia and chronic perifollicular inflammation.
FAPD can be distinguished from CCCA by virtue of its lichenoid histological
features, but the histological overlap with different hair loss
conditions may make it difficult to assign a specific diagnosis.
Fibrosing alopecia in a pattern distribution pathology
The biopsy specimens of patients with fibrosing alopecia in a
pattern distribution as studied by Trueb and Zinkernagel showed
evidence of lichenoid inflammation with destruction of the follicular
basilar epithelium. This inflammation was most evident around the
upper half of the follicle. Terminal hairs (deep-rooted coarse hairs)
as well as vellus hairs (tiny colorless hairs) were affected. Advanced
lesions under the microscope showed perifollicular lamellar fibrosis
(growth of excessive amounts of fibrous tissue) and completely fibrosed
follicular tracts, as seen in end-stage lichen planopilaris, pseudopelade,
or follicular degeneration syndrome.
Fibrosing alopecia in a pattern distribution treatment
During the course of the research study, three patients seemed
to have responded to “antiandrogen” therapy and appeared
to have experienced a halt in the progress of the distinctive form
of alopecia. An antiandrogen obstructs the effects of androgens
(male hormones) normally by blocking the receptor sites. As this
is a relatively newly identified condition, there is very little
research on effective treatment.
Fibrosing alopecia in a pattern distribution conclusions
At the moment then it is not clear exactly how fibrosing alopecia
in a pattern distribution should be categorized. There are at least
two different explanations for the observed scarring. Some patients
with androgenetic alopecia might have additional clinical and histological
features of inflammatory scarring alopecia limited to the area of
hair loss. Androgenetic alopecia as an entity is characterized by
a defined area of progressive non-scarring alopecia. But in such
patients who exhibit fibrosing alopecia in a pattern distribution,
the immune system may recognize miniaturizing follicles as abnormal,
and as a result inflammation targets these follicles. The inflammation
is associated with a lichenoid reaction in the follicles. The inflammatory
activity and miniaturization of the hair follicles continues until
they are destroyed.
An alternative explanation for fibrosing alopecia in a pattern
distribution is that it is a variant of Lichen planopilaris. Lichen
planus, occurring in regions of skin other than the scalp, can also
present itself without lesions and interfollicular inflammation.
Overlapping features make it difficult to distinctly define the
condition, and a lot of research is required before fibrosing alopecia
in a pattern distribution can be separated from lichen planopilaris
or other similar forms of alopecia. Larger numbers of patients (suspected
with having fibrosing alopecia in a pattern distribution) need to
be treated with anti androgens in a controlled manner and the results
evaluated. The main question to be tackled is how the lichenoid
tissue pattern is generated around the individual androgenetic alopecia
affected hair follicle.
Therefore, for the moment, the question remains whether fibrosing
alopecia in a pattern distribution is another form of scarring alopecia
and, if so, where will this new entity fit within the existing classification
of scarring alopecias?
Fibrosing alopecia in a pattern distribution references
- Amato L, Chiarini C, Berti S, Bruscino P, Fabbri
P. Case study: fibrosing alopecia in a
pattern distribution localized on alopecia androgenetica areas
and unaffected scalp. Skinmed. 2004 Nov-Dec;3(6):353-5. PMID:
15538092
- Zinkernagel MS, Trueb
RM. Fibrosing alopecia in a pattern
distribution: patterned lichen planopilaris or androgenetic alopecia
with a
lichenoid tissue reaction pattern? Arch Dermatol. 2000 Feb;136(2):205-11.
PMID: 10677097
- Kossard S.
Postmenopausal frontal fibrosing alopecia.
Scarring
alopecia in a pattern distribution. Arch Dermatol. 1994 Jun;130(6):770-4.
Erratum in: Arch Dermatol 1994 Nov;130(11):1407.
PMID: 8002649
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