Skin nontumor

Spongiotic, psoriasiform and pustular reaction patterns

Pityriasis rosea



Minor changes: 12 November 2021

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PubMed Search: Pityriasis rosea[TI] skin pathology

Natalia Zhovta, M.D.
Viktoryia Kazlouskaya, M.D., Ph.D.
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Cite this page: Zhovta N, Kazlouskaya V. Pityriasis rosea. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skinnontumorpityriasisrosea.html. Accessed December 4th, 2021.
Definition / general
  • Pityriasis rosea is a self limited viral exanthem usually seen in young patients that starts with a herald patch, followed by similar lesions on the trunk
Essential features
  • Pityriasis rosea is a viral exanthem, commonly caused by reactivation of human herpesvirus 6 and human herpesvirus 7
  • Clinically presents with the herald patch manifesting first, followed by disseminated similar patches on the upper trunk
  • Histopathology of pityriasis rosea demonstrates spongiotic pattern
ICD coding
  • ICD-10: L42 - pityriasis rosea
Epidemiology
Sites
  • Skin (usually trunk and extremities), lymphadenopathy
Pathophysiology
Etiology
Clinical features
Diagnosis
  • Clinical examination
  • Skin biopsy
Laboratory
  • Usually not needed to establish the diagnosis
Prognostic factors
Case reports
Treatment
Clinical images

Contributed by Natalia Zhovta, M.D. and Yi Lai, M.D.
Elongated scaly patches

Elongated scaly patches

Inverse patch

Inverse patch

Scaly patches

Scaly patches

Disseminated scaly patches

Disseminated scaly patches

Herald patch

Herald patch

Disseminated patches

Disseminated patches


Herald patch

Herald patch

Disseminated elongated patches

Disseminated elongated patches

Microscopic (histologic) description
  • Subacute spongiotic dermatitis with perivascular lymphocytic infiltrate (Dermatologica 1982;165:551)
  • Mild acanthosis of the epidermis may be present, especially in herald patch
  • Foci of parakeratosis overlying spongiosis
  • Granular layer may be diminished or absent under area of parakeratosis (Indian J Dermatol Venereol Leprol 2000;66:244)
  • Erythrocyte extravasates may be focally present in the superficial dermis
  • Rare presence of dyskeratotic cells and eosinophils may be observed
Microscopic (histologic) images

Contributed by Viktoryia Kazlouskaya, M.D., Ph.D.
Spongiosis with mounds of parakeratosis

Spongiosis with mounds of parakeratosis

Minimal spongiosis with mounds of parakeratosis Minimal spongiosis with mounds of parakeratosis

Minimal spongiosis with mounds of parakeratosis

Spongiosis, parakeratosis, erythrocyte extravasates Spongiosis, parakeratosis, erythrocyte extravasates Spongiosis, parakeratosis, erythrocyte extravasates

Spongiosis, parakeratosis, erythrocyte extravasates


Spongiosis, parakeratosis, superficial lymphocytic infiltrate Spongiosis, parakeratosis, superficial lymphocytic infiltrate

Spongiosis, parakeratosis, superficial lymphocytic infiltrate

Negative stains
  • Fungal stains (PAS, GMS, etc.)
Sample pathology report
  • Skin, biopsy:
    • Subacute spongiotic dermatitis, suggestive for / consistent with pityriasis rosea (see comment)
    • Comment: Biopsy examination demonstrates subacute spongiosis with overlying mounds of parakeratosis. There is a mild inflammatory perivascular infiltrate composed predominantly of lymphocytes with erythrocyte extravasates. No fungal elements were identified with PAS stain. Clinical image was reviewed. Overall, the histopathological features and clinical presentation are consistent with pityriasis rosea or a pityriasis rosea-like drug reaction but only in an appropriate clinical setting. (If clinical images and history are not present, the report may be more descriptive and include differential diagnosis of other spongiotic conditions.)
Differential diagnosis
  • Pityriasis rosea-like eruptions:
    • Triggered by medications or vaccinations
    • Clinically, may be itchier, often display peripheral eosinophilia and tend to persist unless the drug is stopped
    • Histopathologically: often indistinguishable; may have interface and eosinophilia (JAAD Case Rep 2018;4:800)
  • Guttate / eruptive psoriasis:
    • May be very similar clinically and histopathologically
    • Herald patch is usually not present in psoriasis
    • Histopathologically: neutrophils present in the parakeratosis; dilated vessels in the papillary plates are more common (Australas J Dermatol 2020;61:e481)
  • Secondary syphilis:
    • Clinically, may be similar but no herald patch seen
    • Histopathologically: psoriasiform and lichenoid dermatitis with perivascular and interstitial infiltrate with lymphocytes, histocytes and plasma cells
    • Sometimes, the infiltrate may be granulomatous
    • Swollen, prominent endothelial cells are common (J Am Acad Dermatol 2020;82:156)
  • Other eczematous eruptions (contact dermatitis, nummular dermatitis, seborrheic dermatitis):
    • May be indistinguishable histopathologically and clinical correlation is required
    • Although a few eosinophils may be present in pityriasis rosea, large numbers are uncommon
  • Drug eruptions:
    • Variable clinical presentation
    • Histopathology is variable; combination of interface pattern with spongiosis and eosinophil rich infiltrates are common
  • Pityriasis lichenoides:
    • Clinically, may have similar features; however, tends to have a chronic course, no herald patch present
    • Histopathologically: an interface dermatitis and perivascular lymphocytic infiltrate is present with erythrocyte extravasates
    • Presence of neutrophils in the parakeratosis
Board review style question #1

What are the expected histopathological features of this condition?

  1. Spongiosis, mixed perivascular infiltrate with lymphocytes and neutrophils, neutrophils in the stratum corneum and positive PAS stain
  2. Regular psoriasiform acanthosis, perivascular lymphocytic infiltrate, parakeratosis with neutrophils and negative PAS stain
  3. Acute spongiosis, wedge shaped perivascular and interstitial infiltrate with numerous eosinophils
  4. Subacute spongiosis, perivascular superficial lymphocytic infiltrate with erythrocyte exocytosis and mounds of parakeratosis overlying spongiosis
  5. Interface dermatitis, perivascular superficial lymphocytic infiltrate with erythrocyte exocytosis and parakeratosis with neutrophils
Board review style answer #1
D. The condition demonstrated in the picture is pityriasis rosea. The patient has scaly, slightly oval patches localized along Langer lines. Classical histopathological features of this condition are subacute spongiosis, superficial perivascular lymphocytic infiltrate (often with erythrocyte exocytosis) and small mounds of parakeratosis overlying spongiotic areas. The description from choice A corresponds to tinea infection; B) psoriasis; C) arthropod reaction; E) pityriasis lichenoides.

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Reference: Pityriasis rosea
Board review style question #2
What virus plays the most significant role in the pathogenesis of pityriasis rosea?

  1. EBV
  2. HHV6
  3. HIV
  4. HSV1
  5. HSV2
Board review style answer #2
B. HHV6. Although the exact etiology of pityriasis rosea is unknown, the reactivation of HHV6 and HHV7 was reported to play a role.

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Reference: Pityriasis rosea
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