Biomedical Engineering Reference
In-Depth Information
(
A
)
(
B
)
(
C
)
Figure 10.18
(
A
) Mild-to-moderate phototoxic reaction due to sunlight exposure in the 24 hours following an aminolevulinic acid-photodynamic therapy session.
(
B
) Six months postprocedure, the patient demonstrated marked improvement in photodamage without postinfl ammatory hyperpigmentation. (
C
) Four-year
follow-up with durable photorejuvenative effects.
for AKs, with the added benefi t of addressing photoaging.
Clearance of AK lesions with PDT is superior from a cosmetic
standpoint compared with conventional treatments such as
liquid nitrogen (72). In terms of patient satisfaction with PDT,
a study by Tierney and colleagues followed 39 patients treated
with ALA-PDT (71). In this study, patients reported statisti-
cally signifi cant better recovery compared with other treat-
ments, including cryotherapy or surgical excision. A borderline
statistically signifi cant improvement was achieved with PDT
for overall cosmetic outcome and patient satisfaction com-
pared with other therapies. Morton (198) also found that
patients preferred the overall treatment procedure and cos-
metic outcome of ALA-PDT compared with cryotherapy.
Patient satisfaction was high in the stage III clinical trial by
Piacquadio et al. (78) Ninety-four percent of patients thought
the cosmetic results following PDT were good to excellent.
contraindications, partial response, or signifi cant adverse
effects. Oral isotretinoin is the current most effective treatment
that is known to reduce 80-90% of the acne lesions after
4 months of treatment (201,202); however, despite its undeni-
able effectiveness isotretinoin is not a curative drug. Relapse
within 2 years may be seen in up to half of the patients that will
require two or more courses of treatment (203,204). Besides, its
use is associated with many side effects, some of which can be
very serious. The most important issue is its teratogenicity, but
common adverse events include dry skin/lips, ophthalmologic
and gastrointestinal symptoms, and headaches. Laboratory
abnormalities have been described, warranting adequate mon-
itoring of liver functions and serum lipids (205). In addition,
bone mineralization abnormalities (206) and depression (207)
have been reported. PDT and light-based treatments can offer
alternative treatments for acne with their own advantages and
disadvantages.
PDT may promote acne improvement via antibacterial
activity against
P. acnes
, selective damage to sebaceous glands,
reduction of follicular obstruction and hyperkeratosis, and via
immunologic host responses (208,209). Visible light is able to
activate natural endogenous porphyrins produced by
P. acnes
,
generating ROS that destroy the bacteria (209). Therefore, it is
expected that topical application of ALA, producing additional
porphyrins, makes the combination more effective than light
alone (210).
A variety of light sources for the treatment of acne with PDT
have been studied, including noncoherent red and blue light,
PDL, IPL, and a combination of these.
Hongcharu and colleagues (211) fi rst described the effi cacy
of topical ALA followed by light exposure (20% ALA 3 hours,
550-700 nm, 150 J/cm
2
) for acne on the back of 22 subjects in a
randomized controlled study. Porphyrin fl uorescence, sebum
output, and acne severity were measured at baseline and at
intervals after treatment. Histologic examinations have demon-
strated vacuolization of sebocytes and keratinocytes followed
by sustained atrophic glands, granulomatous reaction, and
topical photodynamic therapy
for inflammatory and infectious
dermatoses
Acne Vulgaris
Acne results from the obstruction and infl ammation of the
sebaceous glands, and it affects 80% of the human population.
The pathogenic mechanisms of acne are complex and include
epithelial hyperproliferation, follicular plugging with forma-
tion of comedones, increased sebum production by sebaceous
glands, infl ammation, and the presence and proliferation of
Propionibacterium acnes
within the follicle (199). Acne typi-
cally begins in adolescence with hormonal changes and more
often affects males, but in 30% of women can persist during
the entire fertile period (200). There are several different pre-
sentations of acne ranging from comedonal (blackheads and
whiteheads), papular, pustular, and cystic acne. In many cases,
many of these presentations of acne can be present on an indi-
vidual simultaneously.
The fi rstline treatments for acne vulgaris are conventional
topical and/or oral medications. However, many patients have
