Structure of Nails And Nail Disorders

Nails

Visible portion of nail is known as  Nail plate. Semi-circular white area at proximal part of nail is known as  Lunula. Skin at proximal part of nail is Proximal nail fold. Laterally, skin on either side of nail is known as  lateral nail folds Thin rim of skin attached to nail proximally is known as Cuticle.

Read this blog further to get a quick overview of this important topic for dermatology and ace your NEET PG exam preparation.

Transverse Section of Nail

Visible portion of nail is nail plate; below which nail bed is present 

Behind them, nail matrix is present 

Hyponychia

 Distal junction, where skin is attached to nail plate is k/a Hyponychia Hyponychium is most common site for onychomycosis [fungal infection of nails]Proximal junction, where skin is attached to nail plate is k/a Eponychia Nail Plate develops from Nail Matrix

Paronychia

Infection of Nail folds is k/a Paronychia Acute Paronychia is d/t Staph aureus [i.e Bacterial.Chronic Paronychia is d/t Mixed infection [Bacterial + Fungal]. MC fungi involved is CandidaLunula is visible nail matrix [i.e extension of nail matrix below nail plate]

Pitting of Nails

Small depressions on nail plate dorsally, is k/a Nail pitting It is due to focal parakeratosis [i.e retention of nucleus in stratum corneum] of proximal nail matrix Proximal nail matrix forms dorsal portion of nail plate [Hence, any defect in dorsal nail plate is d/t defect in proximal nail matrix Distal nail matrix forms ventral portion of nail plate Due to presence of nucleus at these sites; mitotic activity is present d/t which these cells proliferate & slough off resulting in small depression. Pitting is seen in:

• Psoriasis 
• Have irregular, deep pits k/a Thimble pitting [thimble is metallic device with pits, used by weavers; to avoid piercing of needle into thumb] 
• Alopecia areata 
• Have regular, superficial pits k/a Geometric pitting 
• Eczema

 Nail Changes Associated With Psoriasis

• IRREGULAR PITTING . It is the most common nail change. It is due to a defect in the proximal nail matrix. OIL DROP SIGN/SALMON PATCH It is most characteristic nail change Defect in nail bed, which appears as if a drop of oil is kept below nail plate 
• Onycholysis [separation of the nail plate from the nail bed]
• Leukonychia [whitening of nail plate] 
• Normally when nails are intact, they appear in pink color.D/t onycholysis, pink color is lost & appear white k/a Leukonychia

Subungual Hyperkeratosis [i.e Thickening of nail bed]

• Nail tunneling 
• Sub-ungual hyperkeratosis results in pushing of nail plate upwards, d/t which nail appears like tunnel 
• Onycholysis, Leukonychia, Subungual hyperkeratosis, Nail tunneling is also seen in ONYCHOMYCOSIS
• KOH mount shows fungus [differentiated from psoriasis]

Dermatology Related Articles:

Nail Changes Seen In Lichen Planus

• Pterygium 

• Wing shaped extension of proximal nail fold resulting in destruction of nail plate it is the Most characteristic nail change seen in Lichen planus 
• Anonychia- Absence of nail plate it is Caused by destruction of entire nail plate by pterygium 
• Pup-Tent Sign- Nail is lifted in central portion which looks like tent
• Onychorrhexis- Longitudinal ridging over nail plate
• LEUKONYCHIA- Whitening of nails .APPARENT LEUKONYCHIA  Nail appears white in color, without separation of nail plate from nail bed 

	·         White small area seen on nail plate is leukonychia ·         It is idiopathic leukonychia which is normal ·         As nail grows it might pass off
Pitting	·         Red, painful, swelling d/t to infection of nail fold is k/a Paronychia [Acute is generally caused by Staph aureus]
Paronychia	·         Red, painful, swelling d/t to infection of nail fold is k/a Paronychia [Acute is generally caused by Staph aureus]
	·         Shows Leukonychia d/t Onycholysis ·         Seen in Psoriasis & onychomycosis
	·         Underlying nail bed becomes thick resulting in yellowish discoloration of nails
	·         Fungus infects nails resulting in onycholysis ·         Surrounding skin is also infected resulting in scaling ·         Pt may have predisposing factors like Diabetes
	·         Transverse lines seen in patients suffering from Thallium or Arsenic poisoning

This is everything that you need to know about disorders of nail  for your dermatology preparation.. For more interesting and informative blog posts like this download the PrepLadder App and keep reading our blog!