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XP
What is XP ?
Rare inherited skin disorderdue to defective repair of DNA
characterized by; photosensitivity
pigmentary changes premature skin aging
early malignant tumor development
How Is It Inherited?
Autosomal recessive
What About Its Presentation?
Is It a Pure Skin Disorder?
Skin
Eyes
Brain
What Are The Tumors That Can Develop In XP ?
BCC
SCC
keratoacanthoma
malignant melanoma
What Is NER?
Nucleotide Excision Repair
It is a mechanism of DNA repairused in repairing UV damage
Nucleotide Excision Repair
NER in the cell
Damage Recognition
Binding of protein complex
3’
Incision of DNA
5’
Oligonucleotide excision
DNA repair synthesis
What Is The Cause Of XP?
DNA damage causes mutations that activate oncogenes
or inactivate tumor suppressor genes
What are The Different Types Of XP?
XP is actually the name of 8 different gene abnormalities in 8 locations
At least 8 different gene abnormalities or complementation groups (XPA to XPG)
varying disease severity
Type Gene Locus
Type A, I, XPA XPA 9q22.3Absent or minimal DNA repair activity
Type B, II, XPB XPB 2q21 Few patients
Type C, III, XPC XPC 3q25 Most common, 1/3 of all patients
Type D, IV, XPD XPDERCC6
19q13.2-q13.3, 10q11
Second most common
Type E, V, XPE DDB2 11p12-p11
Type F, VI, XPF ERCC4 16p13.3-p13.13
Type G, VII, XPG RAD2ERCC5
13q33
Dominant Type
What You Can See In XP Biopsy?
How Can XP Be Treated?
No “cure” for XP exists yet
The best thing to do is to avoid contact with UVR
Reducing exposure to the sun
Sun glasses
Clothing (long sleeves, long pants,
gloves)
Optical filtration
Lots and lots of sunscreens
HOUSING
Halogen or LED lampsSpecial windows are required
everywhere with UV-Blocking films
Isotretinoin may reduce the number of keratosis & prevent formation of new
cancers
early & complete removal of all tumors is essential
Cryo
5-FU
Regular follow-up
Gene Therapy
What Is The Prognosis Of XP?
Many patients with XP die at an early age from skin cancers
Less than 40% of individuals with XP survive beyond age 20 years
However, if a person is diagnosed early ,does not have severe neurological
symptoms, has a mild variant ,
and takes all the measures to avoid UVR,
they may survive beyond middle age
References
dermnetnz.org
Google images
en.wikipedia.org
Bolognia Textbook of Dermatology 3rd ed
Genetic Disease By: Jean Liu (Presentation)
THANK YOU
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