Porcine Juvenile Pustular Psoriasiform Dermatitis

Porcine Juvenile Pustular Psoriasiform Dermatitis (Pityriasis rosea)

Pityriasis rosea is a self‑limiting inflammatory disease of young pigs.
The disease is of unknown etiology.
There is a predilection for the white breeds, especially the Landrace, and suggestions of a hereditary link.
- Although the mode of inheritance is not simple, it is clear that swine that have had this condition are more likely to produce affected progeny.
The condition is noncontagious.
- Experimental attempts at transmitting the disease, and attempts to demonstrate any significant microorganisms have failed.
- The disease has been observed in cesarean‑derived SPF pigs.
The condition most frequently occurs in young pigs, 3‑14 weeks of age, and often more than one member of a litter is affected.
Although this condition had been previously called pityriasis rosea, clinically and pathologically it is nothing like pityriasis rosea in humans!

There are usually no systemic signs. Skin lesions may be preceded by anorexia, vomiting, & diarrhea.
There is no fever.

Primary lesions are seen on the ventral abdomen or medial thighs, and appear as symmetric, sharply defined, red raised plaques up to 6 mm in diameter.
These expand centrifugally, often coalescing to produce whorling mosaic or serpiginous patterns, and may extend up the sides and perineum.
As they expand, lesions become scaly and heal from the center outward, producing ring‑shaped lesions with a center of scaly or normal appearing skin surrounded by a zone of elevated erythematous skin and scales.
- The term pseudo-ringworm has been used to describe this condition.
Lesions are nonirritant and usually resolve spontaneously in 2 ‑ 10 weeks.

Skin biopsy reveals superficial perivascular dermatitis with psoriasiform epidermal hyperplasia.
The superficial dermis usually shows mild to moderate mucinous degeneration, and eosinophils and neutrophils are the predominant inflammatory cell types.
Intra-epidermal pustules containing eosinophils and neutrophils are prominent in early lesions.
Parakeratotic hyperkeratosis is usually prominent.

Dermatophytosis ‑ (etio: Tr. mentagrophytes, M. canis, Tr. verrucosum var. discoides, M. nanum, Tr. rubrum) Ruled‑out due to lack of mycotic organisms.
Exudative epidermitis (greasy pig disease) ‑ (Staphylococcus hyicus) Early lesions may appear as red plaques, but soon become exudative and ulcerated; R/O based on culture, lesion distribution, histopathology.
Dermatosis vegetans ‑ Systemic, erythematous maculopapular dermatitis caused by the inheritance of a autosomal recessive, semilethal factor. Skin, coronary band and hoof lesions, giant cell pneumonia, fatal.
Swinepox ‑ Ballooning degeneration and intracytoplasmic inclusion bodies.

Kate

IL-3 is involved... Vet Path (2007) 34: 45-43