Hair Shaft Disorders Flashcards
(30 cards)
What is this?
Answer:
Monilethrix
= Beaded hair shaft (elliptical nodes 0.7 - 1mm apart separated by narrow internodes)
= breaks easily at constriction sites
What causes Monilethrix?
This disorder is usually inherited
Autosomal dominant
- due to heterozygous mutations in one of three hair cortex-specific keratin genes:
- KRT86,
- KRT81
- KRT83.
There is also an autosomal recessive
- due to mutations in DSG4, which encodes desmoglein 4.
Acquired: anitmitotic medications (chemotherapy), AA
Monilethrix Clinical Presentation
Normal hair at birth
Within the first few months - short, fragile, brittle hairs
“hairs that never grow”
Variable severity
Additional features:
- Keratotic follicular papules
- Syndactyl
- nail (brittle, kolionychia)
- Ocular (cataracts, decreased visual fields)
- Dental abnormalities
What is shown here?
Pili Torti
flattening and 180° twisting of the hair
shaft on its own axis
Causes of Pili Torti
inherited, pili torti can be an isolated abnormality
or it may be a feature of other disorders, including Menkes disease
What Hair shaft defect is seen in Nethertons syndrome?
Trichorrhexis Invaginata = bamboo hair
intussusceptions of the distal shaft (“ball”) into the proximal shaft (“socket”) due
to defective cornification of the cortex
What is the gene in Nethertons syndrome?
SPINK5
What is shown here?
Trichorrhexis Invaginata
What is Trichorrhexis nodosa?
most common of all the structural hair
abnormalities.
characterized by hair shaft fractures in which the individual cortical cells and their fragments splay out, appearing like the ends of two brushes pushed into one another
What is shown here?
Trichorrhexis nodosa
What causes Trichorrhexis Nodosa?
Congenital or acquired.
congenital
- an isolated finding (primary genetic)
- in association with other inherited disorders, e.g. argininosuccinic aciduria, citrullinemia, trichohepatoenteric syndrome
- acquired variant is most commonly caused by repeated trauma
to the hair shaft (chemical relaxation, excessive heat (e.g. hair dryers, hair straighteners [flat irons, hot combs]), frequent brushing, or chronic scratching)
List the clinical variants of Trichorrhexis nodosa?
(1) proximal – usually due to
damage from chemicals and heat;
(2) distal – due to cumulative cuticular
damage; and
(3) circumscribed – occurs in the scalp, moustache, or beard.
What hair defect is shown here?
Trichothiodystrophy
an autosomal recessive disorder characterized by sulfur-deficient hair.
What is trichothiodystrophy?
An autosomal recessive disorder characterized by sulfur-deficient hair
By light microscopy and trichoscopy,
hair shafts have transverse fractures and
alterations in their cuticles
Polarized light is required to visualize the
alternating light and dark bands, i.e. the pathognomonic “tiger tail sign”.
What clinical findings might be associated with trichothiodystrophy?
P: Photosensitivity (type 1 - 3)
I: Ichthyosis
B: Brittle hair
I: intellectual impairment with low IQ
D: decreased fertility
S: Short stature
Some patients may exhibit spasticity, tremors and ataxia, nail dystrophy, dental caries, cataracts, and bony and immune
defects.
The hair usually does not improve with age.
Which hair abnormalities are associated with increased fragility?
Monilethrix
Pili Torti
Trichorrhexis invaginate
Trichorrexis nodosa
Trichothiodystrophy
What is Loose anlagen hair syndrome?
Condition characterised by:
- short blond hair
- diffuse or patchy alopecia
- anlagen hairs can be easily and painlessly plucked from the scalp
MIcroscopic features:
- ruffled proximal cuticle
- absence of root sheath
- bent matrix
What is seen in image B and what is seen in image C
B = Anagen Hair (o = outer root sheath, m = matrix, I = inner root sheath)
C = loose anlagen hair (ragged cuticle, loss of outer root sheath)
T/F : Loose anagen hair syndrome improves with age
True
What is shown here?
Pili annulati
hair shafts that have bright and dark bands when viewed by reflected light
bright bands are related to light scattered from periodically occurring clusters of abnormal, air-filled cavities within the hair.
Is pili annullati inherited?
Can be AD trait or sporadic
Tichoscopic features of pili annulati
alternating white and dark bands
- dark bands are longer
- 20 - 80% of hairs are affected
- bands disappear distally
What is shown here?
Pili Bifurcation
What is shown here?
Pili Trianguli et canaliculi
= Uncombable hair
a rare hair abnormality in which hair has a “spun glass” appearance due to the reflection of light from variably oriented, flattened hair surfaces
Hait is stiff and difficult to comb
