Porcine Juvenile Pustular Psoriasiform Dermatitis

• Also called Pityriasis Rosea
• Occurs in pigs
• Symmetric lesions on the abdomen, loin and medial thigh
• Start as small papules covered by brown crusts
• -> lesions join and spread -> umbilicated plaques containing white centres with erythematous and scaly borders
• Similar to dermatophytosis
• Histologically:
  • Epidermal hyperplasia, parakeratosis, epidermal pustules and superficial perivascular dermatitis
• For more detail see Porcine Juvenile Pustular Psoriasiform Dermatitis

Porcine Juvenile Pustular Psoriasiform Dermatitis (Pityriasis rosea)

General

• 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!

Clinical Signs

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

Gross Lesions

• 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.

Microscopic Lesions

• 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.

Differential Diagnosis

1. Dermatophytosis ‑ (etio: Tr. mentagrophytes, M. canis, Tr. verrucosum var. discoides, M. nanum, Tr. rubrum) Ruled‑out due to lack of mycotic organisms.
2. 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.
3. 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.
4. Swinepox ‑ Ballooning degeneration and intracytoplasmic inclusion bodies.

Postgraduate

Kate

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