Page 143 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 4-58 Rashes

PITYRIASIS ROSEA

Pityriasis rosea is a common idiopathic rash with a
characteristic onset and distribution. It is a self-limited
rash that spontaneously resolves within a few months.
A few distinct clinical variants have been described. The
main goal in treatment is to differentiate pityriasis rosea
from other rashes that can have a similar clinical picture.
Clinical Findings: Pityriasis rosea is a common rash
of young adults and children. It has no racial predilec-
tion. It is most often seen during the spring and fall
months. Clustering of cases has been reported. A small
but significant subset of patients have had a preceding
upper respiratory tract infection. This has led some to
search for a viral cause of the rash, although none have
been found. The rash of pityriasis rosea can have a
varying morphology, but it most commonly begins with
a herald patch. The herald patch, or mother patch, is
the first noticeable skin lesion. It typically precedes the
entire outbreak of pityriasis rosea by a few days. The
herald patch is a 2- to 4-cm, pink-red patch with fine
adherent scale that commonly occurs on the trunk.
After a few days, smaller, oval-shaped patches 0.5 to
1 cm in diameter begin appearing on the trunk and
extremities. The rash follows the skin tension lines and
has a peculiar “fir tree” pattern. This pattern mimics
the down-sloping branches of a fir tree. The rash typi-
cally spares the face and glabrous skin.
Patients may complain of mild to moderate pruritus,
but most are asymptomatic. The main differential diag-
nosis includes guttate psoriasis and, in cases that affect
the palms and soles, secondary syphilis. Pityriasis rosea
is a self-limited, spontaneously resolving rash. It typi- The rash of pityriasis rosea follows the skin tension lines (Langer’s lines).
cally does not last longer than 2 to 3 months. Guttate
psoriasis usually begins after a streptococcal infection
and does not exhibit a herald patch. The teardrop-
shaped patches of guttate psoriasis also do not follow
the skin tension lines, and this fact can be used to dif-
ferentiate the two. Tinea corporis is almost always in
the differential diagnosis of any rash that has a patch-
type morphology and fine surface scale. Tinea corporis
can be easily diagnosed with a microscopic evaluation
of a small scraping of the skin. Widespread tinea is
almost always associated with onychomycosis, and it
is more commonly seen in patients who are taking
chronic immunosuppressive agents or using topical ste-
roids. These traits can be used to help differentiate the
two conditions. The rash of secondary syphilis is the
great mimicker. Any patient who has pityriasis rosea
that affects the palms and or soles should be tested Generalized thin oval patches The palms and soles are typically unaffected in Secondary syphillis
for syphilis. are distributed on the trunk pityriasis rosea. If they are affected, an RPR must affecting the sole
A few unique variants of pityriasis rosea exist. One is following the skin tension lines. be obtained to rule out secondary syphillis.
papular pityriasis rosea. This form more commonly
affects school-aged children with Fitzpatrick type IV, V,
or VI skin. This version tends to be a bit more wide-
spread and more pruritic. Instead of small, oval-shaped the dermis. Varying amounts of extravasated red blood Treatment: No therapy is needed. Most cases are
patches, this variant consists of small (0.5 cm) papules cells are appreciated within the upper dermis. The asymptomatic and mild. Pruritus can be treated with
that have a small amount of surface scale. It runs the stratum corneum shows varying degrees of acanthosis oral antihistamines and adjunctive topical steroids. The
same benign course, with self-resolution after a few and parakeratosis. use of oral erythromycin, twice a day for 2 weeks, was
weeks to months. On healing, postinflammatory hyper- Pathogenesis: Many attempts to isolate a viral or a shown to decrease the duration of the rash. Ultraviolet
pigmentation or hypopigmentation may result and may bacterial element in patients with pityriasis rosea have therapy is very helpful in treating the rash and pruritus.
persist for several months. been met with frustration. To date, no infectious cause If there is any consideration for syphilis in the history
Histology: A superficial and deep lymphocytic and has been determined. The true nature and cause of or the physical examination, a rapid plasma reagin
histiocytic infiltrate is seen surrounding the vessels of pityriasis rosea remain elusive. (RPR) blood test should be performed.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 129