Alopecia areata (AA) is a non-scarring, inflammatory, hair loss disease that is seen in men, women and children. This condition is commonly manifested by patchy areas of hair loss on the scalp and other body areas. In severe cases, alopecia areata can progress to complete loss of all body hair. While not a life threatening condition, alopecia areata is nonetheless serious because of the psychologically and sociologically devastating effects the hair loss can have on the affected individual.
Under normal circumstances, hair growth in each hair follicle occurs in a cycle. There are three main phases of the hair growth cycle; anagen, catagen, and telogen. Anagen is the active growth phase when hair fiber is produced. This is followed by catagen, a period of controlled regression of the hair follicle. Ultimately the hair follicle enters telogen where it is in a so-called resting state. Alopecia areata primarily affects the hair follicle as it enters the anagen phase. Inflammatory cells of the immune system infiltrate around anagen hair follicles and cause them to stop producing hair fiber.
Studies indicate that the initial event in the development of alopecia areata is the premature precipitation of anagen follicles into the telogen, resting state of the hair follicle cycle. Most commonly, hair follicles exit anagen, enter catagen, and then shed the hair fiber upon entering telogen. The follicles may then proceed back into the next anagen growth phase but, because of the continued activity of the disease, produce poor aberrant hair fiber. Such follicles are described as being in a dystrophic anagen state. Some researchers believe the hair follicles continue indefinitely to oscillate between several rapid cycles of dystrophic anagen and telogen states. Others believe many of the follicles are eventually arrested in telogen.
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Causes of Alopecia Areata
When the anagen hair follicles are damaged, it may result in alopecia areata. It has been observed that anagen hair follicles sometimes enter the telogen state prematurely, causing alopecia. When this condition occurs repeatedly, poor aberrant hair fibers are produced from dystrophic anagen follicles. Scientists have two views on the state of the hair follicles in alopecia areata. Some believe that the hair follicles transit rapidly between dystrophic anagen and telogen stages while another school of thought believes that they are arrested in a state of telogen.
Thus in early alopecia areata, the disruption of the normal hair follicle cycling results in a disproportionate ratio of anagen, catagen and telogen hair follicles resulting in clusters of telogen hair falling off from the scalp and other parts of the body. The hair shafts that fall off appear to have roots that indicate telogen hair follicles. At the periphery of the bald patch are found fractured hairs with sharp pointed tips. They are called exclamation mark hairs because they resemble exclamation marks.
When the anagen hair follicles are damaged, it may result in alopecia areata. It has been observed that anagen hair follicles sometimes enter the telogen state prematurely, causing alopecia. When this condition occurs repeatedly, poor aberrant hair fibers are produced from dystrophic anagen follicles. Scientists have two views on the state of the hair follicles in alopecia areata. Some believe that the hair follicles transit rapidly between dystrophic anagen and telogen stages while another school of thought believes that they are arrested in a state of telogen.
Thus in early alopecia areata, the disruption of the normal hair follicle cycling results in a disproportionate ratio of anagen, catagen and telogen hair follicles resulting in clusters of telogen hair falling off from the scalp and other parts of the body. The hair shafts that fall off appear to have roots that indicate telogen hair follicles. At the periphery of the bald patch are found fractured hairs with sharp pointed tips. They are called exclamation mark hairs because they resemble exclamation marks.
Types of Alopecia Areata
On clinical examination, alopecia areata appears as a smooth bald patch, which at times may further expand in size. Similar bald patches may appear subsequently in other areas. Alopecia areata has been classified into different types according to the severity of the disease and its various forms.
On clinical examination, alopecia areata appears as a smooth bald patch, which at times may further expand in size. Similar bald patches may appear subsequently in other areas. Alopecia areata has been classified into different types according to the severity of the disease and its various forms.
Alopecia Totalis: In this the scalp is affected and all the hair from the scalp is lost resulting in a smooth bald head.
Alopecia Universalis: This is a severe form of alopecia where there is loss of all body and scalp hair including eyebrows, eyelashes, underarms and pubic hair.
Alopecia Areata Barbae: When alopecia affects the hair of the beard region, it is known as alopecia areata barbae.
Reticulated Areata Barbae: In this form of disease, bald patches may not be found but there is hair loss in irregular patterns in a net like fashion. In the scalp, there are regions of hair loss interspersed with areas with normal hair growth. When affected with reticulated alopecia, patients may have hair falling from one region but new hair growth in another region. This phenomenon may for many months or years.
Ophiasis type of alopecia areata shows a band like hair loss. It occurs mostly in the temporal or the occipital regions of the scalp and is therefore more difficult to treat, as most medicines have a delayed action on these areas. Ophiasis type of alopecia is identified by a turban or snake like pattern on the periphery of the scalp. Ophiasis in Greek means serpent and this is how the disease gets its name.
Diffusion Type of Alopecia Areata: In this case, there is a premature cessation of anagen growth, which causes partial hair loss throughout the scalp. No distinct patches are evident. It may not be possible to identify the disease clinically, as it can be mistaken for telogen hair loss, which is diffused hair loss caused by stress, certain physical conditions like puberty or childbirth, chronic illness, or trauma. It is also similar to anagen effluvium, which is hair loss in the anagen stage due to chemotherapy or radiation treatment. In some cases of hair loss on top of the head, it also resembles typical male or female pattern of hair loss or even trichotillo where people pull out their own hair. A biopsy is perhaps the best way to diagnose the disease specifically. Dermatologists also look for the exclamation type of broken hairs as indication of alopecia areata.
Perinevoid Alopecia Areata: This is a relatively unusual type of alopecia areata where spots of skin are found having properties different from the surrounding general skin area. Around these pigmented spots or nevi are found patches having characteristics of alopecia areata
NAIL CHANGES
Clinical Features of Nail Changes
It is the structure of the normal nail that decides the clinical features of the affected nail. The clinical features depend on the localization or severity of the disease. If the proximal part of the matrix is affected, then onychorrhexis or brittle nails and irregular pits are seen. If both the distal and proximal parts are affected then a thinned out nail plate is observed. This thinning may be linked to a compensatory hypertrophy of the root of the nail and may lead to complete destruction of the plate and the nail may eventually be shed.
It is the structure of the normal nail that decides the clinical features of the affected nail. The clinical features depend on the localization or severity of the disease. If the proximal part of the matrix is affected, then onychorrhexis or brittle nails and irregular pits are seen. If both the distal and proximal parts are affected then a thinned out nail plate is observed. This thinning may be linked to a compensatory hypertrophy of the root of the nail and may lead to complete destruction of the plate and the nail may eventually be shed.
Nail aberrations, which are clinically attributable to alopecia areata are therefore very varied though they are all expressions of a matrix disease. These nail abnormalities can affect one, some or all nails
Despite considerable work, the causes of such aberrations are by and large still unknown. Some of the common nail aberrations are the following:
Nail pitting: This is the most common nail aberration. The disease causes irregular keratinization on the nails. These irregular keratins fall off from the nails leaving behind depressions or pits.
Onychorrhexis: These are brittle nails having vertical ridges, which sometimes split vertically and peel off.
Onychomadesis occurs when the proximal part of the nail separates from the nail bed, leading usually to shedding. The nail may or may not grow back.
Onycholysis is the separation of the distal part from the nail bed.
Koilonchia: Here the outer surface of the nail acquires both longitudinal and transverse concavity giving it a spoon-like appearance. It is due to thinning out of the nail plate.
Spotting of the lunula is the crescent shaped mark at the base of the nail.
It must be noted that anonychia and scarring have not been observed.
Histology of Nail changes in Alopecia Areata
Nail fragments examined by light and electron microscopy show that nail aberrations are linked to the proximal part. While aberrations are all over the nail plate, maximum aberrations are in the upper proximal while the lower subuangal and the nail bed is almost entirely preserved. The distal part is negligibly affected.
Nail fragments examined by light and electron microscopy show that nail aberrations are linked to the proximal part. While aberrations are all over the nail plate, maximum aberrations are in the upper proximal while the lower subuangal and the nail bed is almost entirely preserved. The distal part is negligibly affected.
Under light microscopy the nail plate is often seen thinned out but total atrophy is rare. There are wave like bands showing architectural disorder of the corneocyte arrangement. Also observed is parakeratososis of variable intensity. That is, the nuclei are either grouped in centers or distributed evenly throughout the plate. It is noticed that changes are more in the upper part and less in the lower part.
Particularly the upper edge shows disintegration and pits. These pits often look like thin parallel slits giving it a flaky appearance. By and large the subuangal layer is not affected and shows only light parakeratososis
Under electron microscopy the shape of the nail plate looks very clearly changed. The cytoplasm is filled with vacuoles of sizes ranging from 140 mm to 1600 mm. The keratin fibre network also looks changed. Some cells distinctly show fiber rarefaction making them look fibrillary. Lastly, the cytoplasm is sometimes seen to contain nuclei and fragments of internalized membranes. The space between cells is increased from 25-35 mm to 100-850 mm. It is still bigger in some places taking on the appearance of an ampular dilation
As under light microscopy, here also, changes are seen concentrated more in the upper part than in the lower part, with the subuangal layer remaining largely unaffected, sometimes hypertrophic.
Both, light and electron microscopy show that the disease affects the upper or the proximal part of the nail plate in a major way, the lower or distal part in a minor way while the subuangal or the nail bed is largely spared. This sort of preferential localization points to a deep disorder of the matrix keratinization.
Light and electron microscopy also show that nail aberrations can take many forms like parakeratososis, parallel slits and arachitectural disorder. These aberrations are seen even in normal nails. In the case of alopecia areata these clinical features are exacerbated. Sometimes in the normal nails cupuliform dips, corresponding to pits, are seen in the upper part of the nail plate. Therefore histology of alopecia areata does not seem to be very specific and, as such, diagnostic conclusions are difficult to arrive at. However, accompanying histological aspects like changes in the upper part of the nail plate, largely spared nail bed, parakeratososis, parallel slits and pits or dips do argue for diagnosis as alopecia areata.
