Page 1498 - Clinical Small Animal Internal Medicine

1436 Section 12 Skin and Ear Diseases

alopecia of the ventral neck, flank, and caudal regions
VetBooks.ir of water spaniels, and alopecia of the caudal thighs of
greyhounds. The actual mechanism of the alopecia is
not known. Because some dogs can regrow normal hair
at these sites, it is thought not to be a follicular dyspla-
sia but more likely a hair cycle abnormality, although
multiple etiologies are possible. The breed associations
suggest a genetic component.

Cyclic Flank Alopecia
Cyclic flank alopecia is a seasonal or cyclic truncal alope-
cia that usually occurs during or just after short day-
length period. The alopecia affects the flanks, lateral
thorax, and sometimes caudodorsum and nose bridge
(Figure 163.6).
There are often bizarre patterns to the alopecia and the
skin may be intensely hyperpigmented. Less common pres-
entations include hypotrichosis and hair pigment changes
without overt alopecia, also in strange patterns. The alope-
cia may not recur each year or in some cases may be perma-
Figure 163.4 Adult male castrated Pomeranian dog with alopecia nent. Age of onset is 1.5–4.5 years. Breeds reported to be
X. Note that the alopecia spares the head and distal extremities, affected by this condition include boxers, English and
similar to hypercortisolemia. French bulldogs, and Airedales (see Table 163.2).

Patterned Alopecia Postclipping Hair Follicle Arrest
Patterned alopecia is a tardive hypotrichosis that often Postclipping alopecia or hair follicle arrest refers to fail-
starts at less than 1 year of age. Many syndromes have ure of hair regrowth following close clipping, usually in
been described that are breed restricted. These include preparation for surgery (Figure 163.7).
pinnal alopecia of dachshunds, ventral and caudal alo- It may occur more frequently in plush‐coated breeds
pecia of dachshunds and Boston terriers (Figure 163.5), and there are two theories as to why this occurs. The first

Figure 163.5 Patterned alopecia in a young adult female spayed Figure 163.6 Alopecia of the lateral thorax and flank in a male
Boston terrier with alopecia of the lateral thorax and ventrum. castrated boxer with cyclic flank alopecia.