An In Vivo Model for Postinflammatory Hyperpigmentation

Post-inflammatory hyperpigmentation (PIH) is an acquired hypermelanosis that occurs after
cutaneous inflammation or injury. This process can occur in all skin types but more
frequently affects darker skinned patients, such as African-Americans, Hispanics, Asians,
Native Americans, Pacific Islanders and those of Middle Eastern descent. PIH can occur after
infection, allergic reactions, contact dermatitis, some medications, burns, following
procedures, or inflammatory disease such as acne. In skin of color, PIH frequently occurs in
resolving acne lesions and can persist for months after the acne lesion itself has
disappeared. In many cases, the resulting PIH can be more distressing than the original
insult.

During the first phase of this study, the investigators investigated the clinical,
spectroscopic and histologic characteristics of acne-induced PIH versus irritant induced PIH
using Trichloroacetic acid (TCA), 35% solution. From this initial study, the investigators
concluded that the similarity of Investigator's Global Assessment scores, and spectroscopic
measurements using Diffuse Reflectance Spectroscopy and Colorimetry in both acne and
TCA-induced PIH at Day 28 suggest that TCA-induced PIH could be a reproducible model for
acne induced PIH.

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules that regulate the
expression of multiple genes at the post-transcriptional level through degradation and
translation of target mRNAs. In the initial study, the investigators hypothesized that
miRNAs derived from melanocytes and immune cells during PIH development could be detected in
tissue and serve as novel biomarkers for PIH and making appropriate therapeutic decisions.
To test this hypothesis, the investigators first examined miRNA gene expression profiles
during PIH development using different models, and then evaluated miRNAs profiles in acne-
induced PIH, TCA- induced PIH and normal skin. The investigators have defined some miRNAs
that potentially are involved in PIH development and may be also serve as the biomarkers for
PIH. The investigators found that there were 19 miRNA changes in acne-induced PIH versus
normal skin, while 43 miRNA changes in TCA-inducedPIH versus normal skin. Interestingly,
about 80% changed genes in acne were included in TCA-mediated miRNA changes, suggesting TCA
can partially mimic acne-PIH.

Overall, this initial model for PIH, using TCA, serves as a foundation to better understand
and improve our ability to manage PIH. In this next phase of the study, the investigators
will refine this in vivo model for PIH by determining the optimal concentration of TCA to
induce PIH.

Inclusion Criteria:

- Patients with types I-VI skin

- Minimum age of 18 years

- Able to understand requirements of the study and risks involved

- Able to sign a consent form.

- Existing truncal acne pustules (at least two on the trunk) with or without history of
post-inflammatory hyperpigmentation

Exclusion Criteria:

- Patients with a recent history of vitiligo, melasma, and other disorders of
pigmentation with the exception of PIH judged to be clinically significant by the
investigator

- Patients with a history of keloids

- Patients with a history of cystic acne or acne conglobata

- Patients on systemic antibiotics or keratolytics (isotretinoin, etc), or topical
antibiotics or keratolytic use (retinoids, benzoyl peroxide) over target areas who
are unwilling to stop these medications for the duration of the study.