What actually happens to the hair when an individual is affected by alopecia areata?
Most of the earlier histopathological studies on the deterioration
of hair follicles in alopecia areata patients were conducted on
scalp tissues of already bald or severely affected individuals.
These studies indicated damage to the upper part of the hair bulbs
while the lower and the root sheath were found to be relatively
normal. Hence alopecia areata was previously identified as a disease
in which there was substantial differentiation in the immune systems
targeting of the cortical keratinocytes.
In this study, the early stages of hair follicle modifications
in alopecia areata were studied. A 13 year old boy who had a patch
of hair loss in his occipital region, was subjected to detailed
histopathological studies. The scalp tissue from his parietal
region was removed and prepared for sectioning by embedding in
paraffin. Longitudinal sections of the tissue were then stained
with hematoxylin and eosin. Hematoxylin is a natural stain obtained
from the heart wood of log wood tree Haematoxylon compachianum
and is a basic stain that reacts with the cell nucleus to stain
it blue or purple. Eosin is a synthetic stain obtained from the
xanthene group of chemicals. It is acidic and reacts with the
basic salts of the cell cytoplasm to color it orange or pink.
The sections were then studied under a light microscope and two
distinct changes in the hair bulb were noticed. The integrity
of the epithelium in the bulb had started deteriorating and there
was a change in the shape of the bulb from its normal inverted
cup shape to round or club shape.
Normally, the hair follicles in the anagen growth phase are
in close physical association with the surrounding dermis. A normal
hair follicle has the following parts. The follicles are embedded
in a matrix. Rows of cells towards the upper region constitute
the upper bulb. This extends upwards to form the pre-elongation
region that develops vertically into the elongation region. Here
the bulb narrows to form a column of cells that are long and have
very sharply defined boundaries due to fibrils piling up against
them. Just above it is the cortical pre keratinization zone. Here
the fibrils are very coarse and many in number. The keratogenous
zone is the next region in which the fibrils are marked and the
cells are crystalline. In patients with Alopecia areata, the anagen
hair bulb disintegrates by way of losing cortical keratinocytes
especially in the upper bulb region, displacement of medullary
cells, and presence of peribulbular lymphocytic infiltrates while
the matrix region remians intact.
The epithelial cells in the follicles are seen to lose their structural identity
and are seen to have degenerating cell nuclei and loss of intercellular integrity.
The changes in the bulbs were very similar to normal catagen follicles but
the frequency with which they occurred were greater in Alopecia areata patients.
The patient was treated with intravenous pulse methyl prednisolone after which
he recovered from drastic hair fall. However he later developed another patch
of hair loss which was treated by injecting corticosteroid into the affected
One of the most characteristic features of alopecia areata is the short broken
hair on the scalp which is referred to as the exclamation mark hair. This
seems to be a result of the above hair follicle disruption process. The process
of degeneration of the follicle and the formation of club shaped root take
a few weeks from the onset of the inflammation. Further histopathological
studies may help scientists evaluate the changes in hair follicles and think
of various methods and medications to alleviate this supposedly autoimmune
What actually happens to the hair when an individual is affected by alopecia areata references
- Ihm CW, Hong SS, Mun JH, Kim
HU. Histopathological pictures of the initial changes of the
hair bulbs in alopecia areata.
Am J Dermatopathol. 2004 Jun;26(3):249-53.