Summary about Disease
Xeroderma Pigmentosum Complementation Group C (XP-C) is a rare, inherited genetic disorder characterized by an extreme sensitivity to ultraviolet (UV) radiation from sunlight. Individuals with XP-C have a reduced ability to repair DNA damage caused by UV light, leading to a high risk of developing skin cancers, eye problems, and neurological abnormalities. XP-C is one of several subtypes of Xeroderma Pigmentosum, each resulting from mutations in different genes involved in DNA repair. XP-C is generally considered to be a milder form of XP compared to some other complementation groups.
Symptoms
Extreme sensitivity to sunlight (photosensitivity)
Severe sunburn with blistering after minimal sun exposure
Freckle-like spots (pigmented macules) on sun-exposed skin
Dry, scaly skin (xeroderma)
Increased risk of skin cancers (basal cell carcinoma, squamous cell carcinoma, melanoma) at a young age
Eye problems (photophobia, conjunctivitis, corneal clouding, cataracts)
Neurological problems (less common than in some other XP groups, but may include developmental delays, intellectual disability, hearing loss, seizures, and progressive neurological degeneration)
Causes
XP-C is caused by mutations in the XPC gene. This gene provides instructions for making a protein that plays a crucial role in nucleotide excision repair (NER), a DNA repair pathway that removes UV-induced damage. Mutations in the *XPC* gene reduce or eliminate the function of this protein, impairing the body's ability to repair UV-damaged DNA. This accumulation of DNA damage leads to the characteristic features of XP-C. It is inherited in an autosomal recessive manner, meaning an affected individual must inherit two copies of the mutated gene (one from each parent) to develop the disorder.
Medicine Used
There is no cure for XP-C, and treatment focuses on managing symptoms and preventing complications:
Strict sun protection: This is the most important aspect of management. Sunscreen (high SPF, broad-spectrum), protective clothing, hats, and sunglasses are essential.
Regular skin examinations: Regular checkups with a dermatologist to monitor for and treat skin cancers.
Treatment of skin cancers: Surgical removal, cryotherapy, topical medications, or other cancer treatments as needed.
Eye care: Regular eye exams and treatment for any eye problems that develop.
Vitamin D supplementation: Due to strict sun avoidance, vitamin D deficiency is common. Supplementation is usually recommended.
Management of neurological problems: Treatment for seizures, developmental delays, or other neurological symptoms, if present.
Is Communicable
No, XP-C is not communicable. It is a genetic disorder caused by inherited gene mutations and cannot be spread from person to person.
Precautions
Strict sun avoidance: Minimize or eliminate exposure to sunlight, especially during peak hours.
Protective clothing: Wear long sleeves, long pants, wide-brimmed hats, and sunglasses when outdoors.
High SPF sunscreen: Use a broad-spectrum sunscreen with a high SPF (30 or higher) on all exposed skin, even on cloudy days. Apply liberally and reapply frequently.
UV-blocking window film: Apply UV-blocking film to windows in homes and cars.
Regular medical checkups: See a dermatologist and other specialists regularly for monitoring and early detection of complications.
Genetic counseling: Families with a history of XP-C should consider genetic counseling to understand the risk of recurrence.
How long does an outbreak last?
XP-C is not characterized by outbreaks. It is a chronic, lifelong condition resulting from a genetic defect. While specific symptoms like sunburns may occur after sun exposure, the underlying genetic vulnerability and increased risk of skin cancer are always present.
How is it diagnosed?
Clinical evaluation: Based on a person's symptoms, family history, and physical examination (especially skin findings).
Photosensitivity testing: Assessing the skin's sensitivity to UV radiation.
DNA repair assays: Measuring the ability of cells to repair UV-induced DNA damage.
Genetic testing: Sequencing the XPC gene to identify mutations.
Timeline of Symptoms
Early infancy/childhood: Often presents with severe sunburn after minimal sun exposure. Freckle-like spots may appear early.
Childhood/adolescence: Dry, scaly skin develops. The risk of skin cancers increases significantly, typically in childhood or adolescence. Eye problems may start to develop.
Adulthood: Continued risk of skin cancers and eye problems. Neurological symptoms, if present, may progress. The severity and rate of progression vary considerably between individuals.
Important Considerations
Early diagnosis and management are crucial: The earlier XP-C is diagnosed, the sooner preventative measures can be implemented to reduce the risk of skin cancers and other complications.
Lifelong sun protection is essential: Strict adherence to sun protection measures is critical for individuals with XP-C throughout their lives.
Multidisciplinary care is needed: Management of XP-C often requires a team of specialists, including dermatologists, ophthalmologists, neurologists, and geneticists.
Psychological support is important: Living with XP-C can be challenging, and psychological support may be beneficial for individuals and their families.
Research is ongoing: Research is continuing to improve understanding of XP-C and to develop new treatments.