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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