Comparison of Hair Follicle Histology Between Horses with Pituitary Pars Intermedia Dysfunction and Excessive Hair Growth and Normal Aged Horses

Innerå, Marie; Petersen, Annette; Desjardins, Danielle R.; Steficek, Barbara A.; Rosser, Edmund J.; Schott, Harold C.

doi:10.1002/9781118644317.ch29

Cited by 4 publications

(5 citation statements)

References 18 publications

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“…On histology, horses affected by PPID have a predominance of hair follicles in a persistent anagen phase (growth) associated with a marked reduction in telogen phase follicles. 7 Horses treated with pergolide showed both improved shedding and proportions of anagen and telogen phase follicles that were not different from those of control horses. 7…”

Section: Clinical Featuresmentioning

confidence: 81%

Integumentary Disorders Including Cutaneous Neoplasia in Older Horses

Knottenbelt

2016

Veterinary Clinics of North America: Equine Practice

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Section: Clinical Featuresmentioning

confidence: 81%

Integumentary Disorders Including Cutaneous Neoplasia in Older Horses

Knottenbelt

2016

Veterinary Clinics of North America: Equine Practice

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“…One study found that telogen hairs represented 75% to 85% of the total number of hair follicles counted in equine normal skin from the neck and rump (Innera et al . ). However, comparison with these numbers is not possible as this ratio varies with species, individual, environmental and metabolic fluctuations.…”

Section: Discussionmentioning

confidence: 97%

Mutually‐induced traumatic alopecia responsive to husbandry modification in two cohabiting donkeys

Brément

Hermange

Degorce‐Rubiales³

et al. 2018

Equine Veterinary Education

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Summary Cutaneous expression of behavioural processes remains unexplored in donkeys. This case report describes a case of traumatic alopecia in two donkeys secondary to mutual hair plucking behaviour. Two genetically unrelated, male castrated, 4‐year‐old Cotentin donkeys living together were presented for a 2‐year history of alopecic, mainly nummular, nonpruritic lesions developing on the back, loin and croup. The general physical examination and behavioural assessment were unremarkable. Trichoscopy, scrapings and cytology were performed. Superficial bacterial infection was diagnosed but a 2‐week course of antibacterial treatment showed no improvement. Histopathological examination showed features compatible with traumatic alopecia and consistent with several behavioural causes of alopecia resembling human trichotillomania or acute traction alopecia, canine traction alopecia, feline self‐induced alopecia and murine barbering. Separation of the donkeys led to complete long‐term remission. Clinical and histopathological findings in our case share lots of similar features with the different mechanical traumatic alopecic disorders mentioned above, making it impossible to simply classify the described affection. Whether alopecic lesions resulted from an exclusive behavioural process (either abnormal excessive mutual grooming or other social interactions) or were associated with underlying causes of pruritus is uncertain. Mechanical alopecia secondary to a behavioural process should therefore be suspected in cases of permanent patchy alopecic nummular lesions on donkeys living in groups.

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“…A recent study characterising hair follicles of horses with PPID found a marked increase in the percentage of the hair follicles that were in the anagen phase compared to normal horses (Innera et al . ). A more correct term for generalised excessive growth pattern is hypertrichosis.…”

Section: Pathophysiology Of Clinical Signs Of Diseasementioning

confidence: 97%

“…Several mechanisms have been proposed for hypertrichosis in PPID including hypothalamic compression due to pressure from the enlarged pituitary and excessive α‐MSH or androgen production; however these theories lack both evidence and a sound theoretical basis (Innera et al . ). Prolactin concentration, either systemically or locally in the skin may also be involved in the abnormal hair growth, as prolactin has been shown to regulate seasonal hair dynamics in a number of other species (Lincoln and Ebling ; Heydon et al .…”

Section: Pathophysiology Of Clinical Signs Of Diseasementioning

confidence: 97%

Pathophysiology and clinical features of pituitary pars intermedia dysfunction

McFarlane

2014

Equine Veterinary Education

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Summary Our understanding of the development and progression of equine pituitary pars intermedia (PI) dysfunction has expanded over the last decade, although much remains to be explained. Degeneration of the hypothalamic periventricular dopaminergic neurons results in disinhibition of the endocrine cells of the PI, the melanotropes. As a result, the PI enlarges, compressing the adjacent lobes, the pars distalis and pars nervosa. The disinhibited melanotropes overproduce pro‐opiomelanocortin peptides, including α‐melanocyte stimulating hormone, β‐endorphin, corticotrophin‐like intermediate lobe peptide and adrenocorticotropin. The excess in PI hormones, perhaps in concert with a deficiency in other pituitary hormones, results in clinical signs of pituitary PI dysfunction. Evidence suggests both oxidative stress and accumulation of misfolded neuronal proteins contribute to damage to the periventricular neurons, although it is not clear if these pathologies actually initiate the disease or are downstream events.

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Comparison of Hair Follicle Histology Between Horses with Pituitary Pars Intermedia Dysfunction and Excessive Hair Growth and Normal Aged Horses

Cited by 4 publications

References 18 publications

Integumentary Disorders Including Cutaneous Neoplasia in Older Horses

Integumentary Disorders Including Cutaneous Neoplasia in Older Horses

Mutually‐induced traumatic alopecia responsive to husbandry modification in two cohabiting donkeys

Pathophysiology and clinical features of pituitary pars intermedia dysfunction

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