Transcript - Abdel Hamid Derm Atlas

Congenital photosensitivity
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Xeroderma pigmentosa
It is a very rare disorder of congenital photosensitivity. 8O& of patients have
a defect in DNA excision repair (classical XP), 2O%have a defect in
daughter strand repair (XP variant) .Patients often present in childhood after
suffering an exaggerated sunburn response. As patients get older, they
develop severe photo damage & multiple skin cancers. Eye & neurological
complications & multiple skin cancer, Eye & neurological complications are
frequently seen, . The gold standard for diagnosis is UV irradiated skin
fibroblast culture, photo provocation & genetic testing are helpful in some
cases. The treatment is with vigorous photo protection, cancer surveillance
& psychological support.
Trichothiodystrophy
Is another very rare recessive disorder of congenital photosensitivity. Up to
5O% of patients have a defective nucleotide excision repair showing
overlap with XP. The degree of photosensitivity is variable& There is NO
increased risk of skin cancer. Other features include chronic ichthyosis
Trichthiodystrophy
J. Investigative Derm. 126: 2147, 2OO6
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B. TTD hair displaying altternating
light & dark tiger tail bands using
polarizing microscope– C,f:
Trichoschisis---d,g :Trichorexisis
nodosa like fracture– e: ribbon like
flattening– J,K: Undulating hair
fiber
Congenital photosensitivity (continue)
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Sparse brittle hair, typical facies, short stature , mental retardation,
erythroderma, eczema, multiple infections, cataracts, dental caries &
hypoplastic nails. TTDNI gene mutations are seen in trichodystrophy.
Diagnosis is made with UV irradiated skin fibroblast culture, monochromator
testing is normal
Cockayne syndrome
It is a congenital disorder that may also overlap with XP showing
photosensitivity, It has autosomal recessive inheritance with significant
variation in phenotypic severity. Patients often present a few hours after sun
exposure when they develop erythematous rash. Over time the rash may
lead to pigmentation & scarring although there is no increase risk of skin
cancer. Other features include short stature, mental retardation, large
hands, feet & ears, eye problems & deafness. The photosensitivity resolves
with age but prognosis is very poor with death before the age of 2O from
progressive neurological demyelination
Cockayne syndrome
Congenital photosensitivity (continue)
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Rothmund- Thomson syndrome
It is a rare autosomal recessive congenital syndrome related to a DNA
helicase mutation. It is characterized by the development of prominence
poikiloderma within the first year of life. Other features include
photosensitivity , warty hyperkeratosis, cataracts, short stature, skeletal
dysplasia & increased risk of Bowen’s disease & osteosarcoma. The gene
responsible for Rothmund- Thomson syndrome is RecQL4.
Kindler syndrome
It is another rare autosomal recessive congenital photosensitivity syndrome
with poikiloderma. Mutation in the Kind-I gene lead to a defect in actin
binding in the extra cellular matrix. Patients develop blistering & skin fragility
in infancy that include progressive & generalized pokiloderma, diffuse
cutaneous atrophy, palmer hyperkeratosis, gingivitis, urethral, esophageal &
anal stenosis
Rothmund –Thomson syndrome
Congenital photosensitivity (continue)
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Smith- Lemi –Opitz syndrome
It is an autosomal recessive congenital disorder of cholesterol synthesis.
Two third of patients photosensitivity with an exaggerated sunburn response
to UVA. Other features include mental retardation, ambiguous genitalia,
dysmorphic facies, failure to thrive, cleft palate, congenital heart disease &
polydactyly. DHCR7 mutations are seen in Smith-Lemi- OPitz syndrome.
Treatment include photoprotection and a high cholesterol diet.
Bloom’s syndrome
It is another autosomal recessive congenital photosensitivity disorder. It is
rare & most commonly seen in Jews, Features include groth retardation,
typical facies, telangiactasia & erythema of sun exposed skin, hyper & hypopigmentation & significant immunodefeciency.There is very high risk of
malignancy especially leukemia, gastrointestinal, breast and skin cancer. A
mutation is seen in the BLM gene that has a role in DNA replication forks
Smith-Lemi Opitz syndrome
Bloom syndrome