Page 144 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 4-59 Integumentary System

Islands of sparing appear as normal areas of skin
within a sea of redness. Patients with pityriasis
rubra pilaris often have erythroderma with a few
islands of sparing.

PITYRIASIS RUBRA PILARIS

Pityriasis rubra pilaris (PRP) is an idiopathic rash that
has many cutaneous manifestations. It is an uncommon
entity that often manifests with near-erythroderma.
There are several clinical variations of the condition,
and it has a characteristic histological pattern, although
this pattern is not always seen on microscopic
examination.
Clinical Findings: PRP has a unique bimodal age of
distribution, with an early onset of disease in the first 5
years of life and adult onset in the sixth decade. There
is no gender or racial predilection. PRP tends to run a
chronic course. It starts insidiously with small follicular,
keratotic, pink to red papules. These papules have been
described as “nutmeg grater” papules. The papules
coalesce into larger patches and plaques. Eventually,
large surface areas are involved, with a near-erythro-
derma. Characteristic islands of sparing occur within
the erythrodermic background. These islands of
completely normal skin are usually small, a few centi- Carnauba wax–like thickening of the palms
meters in diameter, but they can be much larger. The and soles is a common clinical finding in
islands typically have an angulated shape, and they are pityriasis rubra pilaris.
rarely perfectly round or oval. The palms and soles
become thickened and yellowish. This is highly charac-
teristic of PRP and is called “carnauba wax–like” palms
and soles. Fissuring is very common within the kerato-
derma and can be a source of pain and a site for second-
ary infection.
PRP has historically been separated into five sub-
types: classic adult, classic juvenile, atypical adult, atypi-
cal juvenile, and a circumscribed or localized form. The
classic adult and classic juvenile forms were described
earlier. They typically run a chronic clinical course,
with most cases spontaneously resolving a few years
after onset. Paraneoplastic variants of PRP have been
described. Onset of the malignancy precedes the rash
of PRP, and the patients seem to improve with treat-
ment of the underlying tumor. This is a very rare
clinical scenario. Patients with human immunodefi-
ciency virus infection seem to be at a higher risk for
developing PRP.
The differential diagnosis of classic forms of PRP
includes psoriasis, drug rash, and cutaneous T-cell
lymphoma. Skin biopsy and clinical pathological cor-
relation help the clinician make a firm diagnosis. Histology: The pathognomonic histological finding Topical corticosteroid wet wraps, oral retinoids, and
Pathogenesis: The etiology is undetermined. Theo- in PRP is the appearance of alternating layers of para- ultraviolet therapy have long been used as first-line
ries on the formation of PRP have centered on keratosis and orthokeratosis, both in a vertical and a agents. The retinoids are considered first-line therapy,
abnormal metabolism of vitamin A or an abnormal horizontal direction, lending the appearance of a chess and both isotretinoin and acitretin have been used.
immune response to a foreign antigen. These theories board. This pattern is not always present, and some- Other immunosuppressants have been used, including
have not been thoroughly studied or proven. The times it can be seen only with close inspection. methotrexate, azathioprine, and the newer anti–tumor
report of a familial form of PRP may shed some light Treatment: Therapy for PRP is difficult. Many necrosis factor inhibitors. No randomized, placebo-
on the etiology. agents have been used with varying degrees of success. controlled trials have been performed to date.

130 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS