histological improvement compared with vehicle.137 Topical
tretinoin has been shown to increase viable epidermal thickness
and create a more undulating dermoepidermal junction
with prominent rete ridges, as well as effecting other dermal
changes such as increased glycosaminoglycan deposition and
elastic fibers and the formation of new blood vessels.137
Multiple Miliary Osteoma Cutis
A case study suggests that topical tretinoin 0.05% may decrease
the number and size of papules after 3 months of treatment.138
Currently, tretinoin is approved by FDA to treat AV and photodamage.
However, through 40 years of research and clinical use,
topical tretinoin has also been shown to be safe and effective in
treating a range of other diseases and conditions, both as monotherapy
and in combination with other agents. These conditions
include skin and pigmentation disorders, lesions of the oral mucosa
and the ocular surface epithelia, hypertrophic scarring, and
various infections. Although topical tretinoin is associated with a
number of application-site AEs, newer formulations and modes of application have been shown to reduce irritation potential.
The list of diseases for which the effectiveness of topical tretinoin
has been evaluated is remarkably diverse. This is, in part, a testament
to the complexities of retinoid biology and the protean
consequences and advantages of interacting with retinoid receptors.
Some clinical uses of tretinoin appear to take advantage of
its keratolytic action, allowing increased penetration of medications
with which it is coapplied, thus improving their efficacy.
Although it is difficult to imagine adding to the multitude of
conditions listed here, additional uses of topical tretinoin will
no doubt be reported in the future. In our continuing efforts
to provide advice on evidence-based medicine for our patients
and to provide rationale for managed care companies, we
look forward to additional clinical trials to further elucidate the
beneficial effects of tretinoin on the skin. Such studies will undoubtedly
also help us in our efforts to better understand the
complex interactions of retinoids in the human body.