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Skin - Atrophy

Image of atrophy (normal comparison) in the skin from a female F344/N rat in an acute study
Normal skin in a control female F344/N rat from a 14-day repeated-dose study.
Figure 1 of 4
Image of atrophy in the skin adnexa from a male B6C3F1 mouse in a chronic study
Adnexal atrophy-smaller and reduced numbers of pilosebaceous units (arrows) in a male B6C3F1 mouse from a chronic study.
Figure 2 of 4
Image of atrophy in the skin adnexa from a male B6C3F1 mouse in a chronic study
Adnexal atrophy-smaller and reduced numbers of pilosebaceous units (arrows) in a male B6C3F1 mouse from a chronic study.
Figure 3 of 4
Image of atrophy in the skin adnexa from a male B6C3F1 mouse in a chronic study
Adnexal atrophy-severe adnexal atrophy in which adnexa are absent in a male B6C3F1 mouse from a chronic study.
Figure 4 of 4
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comment:

Adnexal atrophy is characterized by smaller and reduced numbers of pilosebaceous units ( Figure 2image opens in a pop-up window and Figure 3image opens in a pop-up window ). In severe cases, the adnexa may be absent ( Figure 4image opens in a pop-up window ). This lesion may be accompanied by inflammation in the dermis. Follicular atrophy is characterized by smaller and reduced numbers hair follicles, and sebaceous gland atrophy is characterized by smaller and reduced numbers of sebaceous glands. Adnexal or follicular atrophy may correspond to the gross observation of alopecia.

The gross appearance of alopecia may be attributed to behaviors such as hair chewing or barbering, mechanical denuding due to rubbing against poorly constructed openings for feeders or water devices, parasitic infestations, and systemic diseases from hormonal (hypothyroidism) and nutritional imbalances. Some agents may affect a specific phase of the hair cycle, resulting in alopecia. For example, many chemotherapeutic agents interfere with the rapid mitotic activity of hair follicles in the anagen phase. Other compounds are known to affect hair follicles in the telogen phase, such as thallium, triparanol, and coumarin. Some compounds, such as phenyl glycidyl ether and dixyrazine, have effects on both the anagen and telogen phases. Follicles affected in a particular phase are likely to appear atrophied. Alopecia with atrophy or complete loss of hair follicles may also occur in skin over a subcutaneous or dermal neoplasm.

recommendation:

If atrophy of both hair follicles and sebaceous glands is present, the term “Skin, adnexa – Atrophy” should be used. If follicular atrophy occurs without involvement of other adnexal structures, the term “Skin, Follicle – Atrophy” should be used. If sebaceous gland atrophy occurs without involvement of other adnexal structures, the term “Skin, Sebaceous gland – Atrophy” should be used. Whenever present, adnexal atrophy, follicular atrophy, or sebaceous gland atrophy should be diagnosed and assigned a severity grade. If these are present as a secondary lesion to neoplasia, chronic inflammation, or fibrosis, it need not be diagnosed but should be described in the pathology narrative.

references:

Elwell MR, Stedman MA, Kovatch RM. 1990. Skin and subcutis. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, 261-277.
Abstract: http://www.ncbi.nlm.nih.gov/nlmcatalog/9002563

Klein-Szanto AJP, Conti CJ. 2002. Skin and oral mucosa. In: Handbook of Toxicologic Pathology, 2nd ed (Haschek WM, Rousseaux CG, Wallig MA, eds). Academic Press, San Diego, 2:85-116.
Abstract: http://www.sciencedirect.com/science/book/9780123302151

Peckham JC, Heider K. 1999. Skin and subcutis. In: Pathology of the Mouse: Reference and Atlas (Maronpot RR, Boorman GA, Gaul BW, eds). Cache River Press, Vienna, IL, 555-612.
Abstract: http://www.cacheriverpress.com/books/pathmouse.htm