Subungual ectopic hair (Onycotrychia)

Sonographic Comparison of Morphologic Characteristics Between Pilonidal Cysts and Hidradenitis Suppurativa

“…The development of ectopic sites of hair growth that include the complete hair follicle with the bulb and tract have been also reported in the nail bed, something different from the finding of subungual fragments of hair tracts in some occupations such as hairdressing …”

“…The development of ectopic sites of hair growth that include the complete hair follicle with the bulb and tract have been also reported in the nail bed, something different from the finding of subungual fragments of hair tracts in some occupations such as hairdressing. 31,32 Furthermore, it has been described that hair follicles, experimentally transplanted to the injured spine of mice, produced long hair tracts from the spinal cord. 33 This finding may mean that the presence of chronic trauma can promote the growth of longer hair tracts.…”

Subungual ectopic hair studied by scanning electron microscopy

“…As far as we know, only three other cases of subungual hair were previously published in literature, two of them in children and one in a 37-year-old female. [3][4][5] Ectopic hair growth has been rarely reported in areas that do not contain hair follicles such as the glans penis and gingiva. 4 The cause for subungual growth of a hair follicle is not defined but a developmental hamartomatous origin of such folliculogenesis is the most likely reason.…”

“…1,2,4 The pigmented variant has been described as spreading pigmented AK (SPAK) in the literature. 2,5 In previous treatment guidelines, 'hypertrophic' and 'hyperkeratotic' appear to be synonymous with thicker lesions, but there was no clear distinction as to whether these represent different clinical AK entities. 3,4,6 The AKTeam TM expert clinicians addressed the semantics of both terms in their editorial and prefer to use the term 'hyperkeratotic' for clinically unsuspicious AK with thicker scale in their proposed treatment algorithm.…”