HYPONYCHIUM ABNORMALITIES Congenital Aberrant Hyponychium vs. Acquired Pterygium Inversum Unguis vs. Acquired Reversible Extended Hyponychium: a proposed classification based on origin, pathology and outcome.

BACKGROUND: Pterygium Inversum Unguis (PIU) is a wing-like extended hyponychium associated with the absence of the distal groove. Although a rare condition, it has been described with different names, confusing both the investigator and the reader. OBJECTIVE: We propose a new nomenclature based on tissue origin and pathology, to account for these conditions. 1) Congenital Aberrant Hyponychium 2) Acquired Pterygium Inversum Unguis 3) Acquired Reversible Extended Hyponychium. MAIN OBSERVATIONS: We report a case of a 19-year-old male, with epidermal pigmentation abnormalities, who had painful fingertips of both index fingers and thumbs since he was 13. He therefore let his finger nails grow very long, minimizing painful contact with the hyponychium. Removal of the aberrant hyponychium revealed glomus bodies aggregates with increased nerve fibers. Subsequently after excision of the hyponychium, his pain was resolved. SUMMARY: Congenital, transient or permanent changes in the hyponychium should be named and classified according to tissue origin to avoid nomenclature confusion.

Finger and toenail onycholysis.

Onycholysis - the separation of the nail plate from the nail bed occurs in fingers and toenails. It is diagnosed by the whitish appearance of the separated nail plate from the nail bed. In fingers, the majority is caused by trauma, manicuring, occupational or self-induced behavior. The most common disease producing fingernail onycholysis is psoriasis and pustular psoriasis. Phototoxic dermatitis, due to drugs can also produce finger onycholysis. Once the separation occurs, the environmental flora sets up temporary colonization in the available space. Finger onycholysis is most common in women. Candida albicans is often recovered from the onycholytic space. Many reports, want to associate the yeast as cause and effect, but the data are lacking and the treatment of the candida does not improve finger onycholysis. A reasonable explanation for the frequent isolation of Candida and Pseudomonas in fingernail onycholysis in women, is the close proximity the fingers have to the vaginal and gastrointestinal tract. Fifty per cent of humans harbour C. albicans in the GI tract and it is frequently carried to the vagina during hygienic practices. Finger onycholysis is best treated by drying the nail 'lytic' area with a hair blower, since all colonizing biota are moisture loving and perish in a dry environment. Toenail onycholysis has a very different etiology. It is mechanical, the result of pressure on the toes from the closed shoes, while walking, because of the ubiquitous uneven flat feet producing an asymmetric gait with more pressure on the foot with the flatter sole.

Opportunistic toenail onychomycosis. The fungal colonization of an available nail unit space by non-dermatophytes is produced by the trauma of the closed shoe by an asymmetric gait or other trauma. A plausible theory.

Opportunistic onychomycosis is defined, when a non-dermatophyte mould is cultured from an abnormal nail unit in the absence of a dermatophyte. The presumption is that the mould has caused the abnormal clinical appearance of the nail unit, yet there are no data available to substantiate this claim. Reports have only identified the mould being recovered from the nail unit niche. A review of the published dermatologic literature describing toenail opportunistic onychomycosis by non-dermatophyte fungi has shown toenails with onycholysis, nail bed (NB) keratosis and nail plate surface abnormalities. The appearance of these clinical changes is indistinguishable from the diagnosis of the Asymmetric Gait Nail Unit Signs (AGNUS). AGNUS is produced by the friction of the closed shoe in patients with an asymmetric gait, resulting primarily from the ubiquitous uneven flat feet. Most commonly, species of Acremonium (Cephalosporium), Aspergillus, Fusarium, Scopulariopsis and rarely species of many different fungi genera are capable of surviving and reproducing in a keratinous environment and change the clinical appearance of the involved nail unit. AGNUS toenails predispose to the colonization by the non-dermatophyte opportunistic fungi but not by dermatophyte fungi.