Def Nail dystrophy
Any abnormality of the fingernail(s) and/or toenail(s) including abnormalities of:
- Shape
- Colour
- Texture
- Growth
Def Onychomycosis
- Any fungal infection of the nails. (Any fungal infec of nail)
- This includes dermatophyte and non-dermatophyte infections.
- Examples: Fusarium spp., Aspergillus spp., Candida spp.
Def Tinea unguium
- Dermatophytic onychomycosis (i.e., dermatophyte infection of the nails)
- Accounts for about 90% of onychomycosis
- Examples: T. rubrum, T. interdigitale, T. tonsurans, and E. floccosum.
Predisposing factors
Local factors
- Chronic tinea pedis (athletes foot)
- Chronic paronychia (→ candida spp)
- Trauma or other nail disorders
Host factors
- Poorly controlled diabetes mellitus
- Immunosuppressione.g.,HIV
- Peripheral vascular disease (decreased blood flow to the feet)
Environment
- Occlusive footwear
- Sweating
How do fungi enter the nail?
- distal/lateral subungual (most common)
- invasion via the hyponychium - superficial white
- direct penetration into the dorsal surface of the nail plate - proximal subungual (rare)
- invasion under the proximal nail fold
- usually immunocompromised hosts - mixed pattern
- ≥2 of the above patterns in the same nail
How do fungi affect the nails?
Cause destruction of keratin in the nail
- Subungual hyperkeratosis (keratin debris under the nail plate)
- Crumbling
- Thickening
- Discolouration
- Nail plate destruction
What is paronychia?
- Inflammation of the nailfold (usually proximal)
- Can be divided into acute and chronic forms
Importance of the cuticle
The cuticle (eponychium) acts as a seal to prevent irritants and pathogens entering beneath the proximal nailfold.
Acute paronychai
Mechanism
Pathogens
Nail biting or sucking
Manicures
Ingrown toenails
Medications e.g. oral retinoids
⬇️
Minor trauma
⬇️
Post of entry for infections
Pathogens
- Usually caused by bacterial infection
• Staphylococcus aureus or Streptococcus pyogenes
- Recurrent acute paronychia
• Herpes simplex virus (‘herpetic whitlow’)
Chronic paronychia
Mechanism
Pathogens
Occupations that involve wet work, irritant contact dermatitis of hands
⬇️
Disruption of cuticle
⬇️
Irritants enter (esp. H20) causing inflammation at proximal nailfold
Pathogens
- Chronic paronychia is caused by irritants (esp H20) and is not primarily an infection.
- However, secondary infections do occur, typically Candida (e.g., Candida albicans).
Nail dystrophy
Causes
- Infections (see lecture on fungal nail infections)
- Benign or malignant growths
- Cysts
- Systemic diseases
Nail dystrophy: asymmetric involvement
- Think about an external cause e.g., dermatophyte infection
- If only 1 nail involved, think about a local problem e.g., cyst or tumour
Nail dystrophy: symmetric involvement
Think about an internal cause i.e., systemic diseases
What is clubbing?
- Enlargement of the soft tissue of the digits.
- Bulbous appearance
- Enlarged, curved nail plate
- Angle between proximal nailfold and nail plate widened to >180 degrees
Clubbing
Associated conditions (congenital & Acquired)
Congenital
- Cystic fibrosis
- Congenital cyanotic heart disease
Acquired
- Bronchopulmonary disease
• Neoplasms (primary or metastatic cancers, pleural tumors)
• Chronic infections (abscesses of the lungs, tuberculosis)
• Bronchiectasis
• Pulmonary fibrosis
• Sarcoidosis
- Cardiovascular disease e.g., bacterial endocarditis
- Gastro-intestinal disease e.g., chronic active hepatitis, IBD
- Endocrine disease e.g., hyperthyroidism
- Other
Clubbing
Mechanism
MECHANISM UNCERTAIN
Theory:
- Whole megakaryocytes enter systemic circulation instead of being fragmented into platelets in the lungs
- Become impacted in fingertip circulation
- Release PDGF
- Increase in fibroblasts, vascular smooth muscle cells
- → clubbing
What is yellow nail syndrome?
- Slow nail growth
- Nails appear thickened
- Increased longitudinal curving
• Loss of cuticle
• Yellow colour
Yellow nail syndrome
Causes
- Pathophysiology still unknown
- Associated conditions:
• Chronic lymphedema
• Respiratory diseases
• Chronic bronchitis
• Bronchiectasis
• Pleural effusions
Apparent leukonychia
Def
Examples
Leuko-
- White
-nychia
- nails
‘Apparent’
- Nail plate is not truly white
- The problem is in the nail bed
- When you apply pressure to the nail, the white colour disappears
Examples:
- Muehrcke’s nails
- Half and half nails (also called Lindsay’s nails)
- Terry’s nails
Apparent leukonychia: Muehrcke’s nails
- Multiple transverse bands parallel to lunula
Associations: - Hypoalbuminaemia (nephrotic syndrome, malnutrition, liver disease). Mechanism may be oedema of the nailbed.
- Chemotherapy. Mechanism unknown.
Apparent leukonychia: half and half nails
Def
Associations
Mechanism
- Apparent leukonychia of proximal half of nail
Associations:
- Normal variant
- Chronic renal disease
Mechanism:
• Uncertain
• Nail plate may be more loosely attached to nailbed proximally
Apparent leukonychia: Terry’s nails
Def
Associations
Mechanism
- The whole nail is white, except for approx. 2mm band at the distal end.
Associations
- Normal variant
- Liver cirrhosis (but non-specific)
Mechanism
- Uncertain
Abnormal capillaries in proximal nail fold
- Seen in autoimmune connective tissue diseases:
• Dermatomyositis and systemic sclerosis
• These diseases damage the small capillaries of the PNF - May only be visible on capillaroscopy or dermoscopy.
- Instead of regular capillary loops, see:
• Decreased capillary density (dropout, avascular areas)
• Giant capillaries
• Enlarged/ dilated capillary loops
Patient with systemic sclerosis.
N – nail
G – giant capillaries
A – avascular areas
D – dilated capillary loops
HIV and the nail
- Fungal nail infections
o Proximal subungual pattern
o Candida onychomycosis - Longitudinal melanonychia (but there are many other causes of this e.g., familial, drug-induced, melanoma, other)
- HPV-induced SCC
- Drug-induced (Zidovudine)
