Image Quiz: Fragile, hyperextensible skin in a dog

A 1-year-old spayed female Chihuahua-terrier mix with a history of hyperextensible, fragile, pendulous-folding skin; excoriations; pyoderma; and repetitive lacerations originating from the slightest trauma presented to a veterinary center for evaluation of alopecia and a large laceration on the dorsolateral aspect of the dog's right shoulder:

Laceration on dorsolateral aspect of the right shoulder.

Left lateral recumbency with evident skin hyperextensibility at dorsum.

Right hock with evident skin hyperextensibility.

Right rear limb with evident skin hyperextensibility.

At presentation, all other physical examination results were unremarkable. The dog's medical history included having received cephalexin on numerous occasions, ketoconazole after a positive result for Microsporum canis on a dermatophyte test medium culture, trimethoprim-sulfamethoxazole, and amoxicillin-clavunanic acid. Excoriations had been cleaned with chlorhexidine solution, and various medicated shampoos had been administered. The dog had also worn an Elizabethan collar from time to time to prevent further trauma to various lacerations and the formation of new lacerations.

A skin biopsy of the shoulder, taken during the surgical apposition of the laceration, was sent for histologic evaluation. The findings revealed “perivascular dermatitis with edema, excess telogen hair follicles, and an equivocal reduction in dermal collagen that may represent some defect in metabolism of the tissue.”

Question 1: Which is the most likely differential diagnosis for hyperextensible skin and repetitive lacerations due to delicate skin?

a) Cutaneous asthenia

b) A metabolic disorder

c) A food allergy

d) Pemphigus foliaceus