@genetic-counselor
Genetic Counselor
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Yes, and this is a key difference from sporadic stomach cancer, which typically appears after the age of 60 years. In families with Hereditary Diffuse Gastric Cancer, cancer has been diagnosed in individuals in their 20s and 30s, occasionally even in the late teens. Because of this, international guidelines recommend that genetic counselling and CDH1 gene testing be considered starting around age 18–20 in families with a known mutation or a strong family history, even if the person feels completely healthy. A young age at diagnosis in a relative especially under 50 years of age is itself one of the red flags that should prompt a genetics referral, rather than being dismissed as “too young to worry about stomach cancer.”
This is one of the most important things to understand: in its early stages, Hereditary Diffuse Gastric Cancer very often causes no symptoms at all. Because the cancer spreads as scattered cells rather than a lump, people can have microscopic disease for years with a completely normal-feeling stomach. When symptoms do appear, they tend to be non-specific and easy to dismiss, such as:
*Persistent indigestion or a feeling of fullness after small meals
*Unexplained weight loss
*Mild, ongoing stomach discomfort or bloating
*Difficulty swallowing or a sense of food “sticking”
*Unexplained low red blood cell count (anaemia) or fatigue, from slow, low-level blood loss
*Nausea or occasional vomiting
Because these symptoms overlap heavily with common conditions like acidity or stomach lining inflammation, they’re frequently overlooked, which is exactly why genetic testing and surveillance matter more than symptom-watching alone in at-risk families.Hereditary Diffuse Gastric Cancer is an inherited condition that sharply raises the lifetime risk of a specific type of stomach cancer called diffuse-type gastric cancer. Unlike sporadic (non-inherited) stomach cancer, which usually forms a visible lump or ulcer, diffuse-type cancer spreads as individual cancer cells through the stomach wall without forming a distinct tumour mass. This makes it harder to detect on a routine endoscopy, even when cancer is already present. Hereditary Diffuse Gastric Cancer is most often caused by a variation in the Cadherin 1 (CDH1) gene, which normally helps cells stick together properly; when it doesn’t work, cells can grow and spread abnormally. Some families with Hereditary Diffuse Gastric Cancer also carry mutations in the Catenin Alpha 1 gene.
Chromosomal conditions occur when there’s an extra, missing, or rearranged chromosome, rather than a change within a single gene. Down syndrome, for example, is caused by an extra copy of chromosome 21. These conditions are typically detected through prenatal screening, prenatal diagnostic testing, or a karyotype test after birth.
A hereditary cancer syndrome is an inherited gene change that significantly increases a person’s risk of developing certain cancers, often at a younger age than usual. Identifying this early allows for closer monitoring, preventive steps, and informed decisions for the person and their family.
Yes. Some heart conditions, such as certain heart rhythm disorders and structural heart defects, have a genetic basis and can run in families. Identifying a genetic cause can help guide monitoring for the patient and screening for close relatives.
The same gene change can show up differently between individuals due to factors like other genes present, environmental influences, and natural variation in how the condition expresses itself. This is why two people in the same family with the same gene change can have very different experiences.
Yes. Broader tests like whole exome or whole genome sequencing are specifically designed for situations where a diagnosis hasn’t been found through other means. They look across many genes at once and can sometimes identify a cause that more targeted testing missed.
Yes. Some genetic conditions only show symptoms later in life, such as certain heart conditions, hereditary cancers, or neurological conditions. A person can carry a gene change for years without any signs before it becomes apparent.
Some signs that may point to a genetic cause include delayed developmental milestones, unusual facial features, slow growth, repeated infections, or health issues affecting multiple body systems. Having these signs doesn’t confirm a genetic condition, but they’re worth discussing with a geneticist.
This depends on the specific condition and its severity. Options generally include additional testing to confirm the diagnosis, specialist consultations to understand what the condition means for your child, and discussing the full range of choices available to you with your care team.
Yes. Once the specific gene change is identified in your family, future pregnancies can often be early via prenatal testing to check whether the same condition has occurred again, giving you more information for planning.
This can be worth discussing with a genetic counselor, especially for communities with a known higher carrier rate for certain conditions. Pre-marital or pre-conception carrier screening can help couples understand their risk and plan ahead.
While response rates are impressive, several practical considerations apply:
*New lesion risk during treatment: xeroderma pigmentosum patients on anti-PD-1 therapy may develop new keratoacanthomas or squamous cell carcinoma in already photodamaged skin, thought to arise from immune activation combined with the underlying DNA repair defect. This is manageable but requires close dermatologic follow-up during treatment.
*No substitute for photoprotection: Immunotherapy treats existing malignancy as it does not reduce ongoing UV-driven mutation accumulation. Strict sun avoidance must continue throughout and after treatment.
*Small evidence base: Total published/reported xeroderma pigmentosum patients treated with immune checkpoint inhibitors remain in the dozens, not hundreds, so while trends are consistently positive, guidelines are based on case-level and cohort-level evidence rather than large trials.
*Multidisciplinary care is essential: Oncology, dermatology, ophthalmology, and (where relevant) neurology should coordinate, since xeroderma pigmentosum is a multisystem condition and cancer treatment decisions affect overall disease management.ICI therapy should be considered specifically for XP patients with metastatic, unresectable, or recurrent skin cancers where surgery and radiation are no longer viable options.
Yes, several published cases support efficacy across different cancer types in XP patients:
*Melanoma: A patient with XP and metastatic cutaneous melanoma treated with pembrolizumab for one year achieved a rapid and complete response of the metastatic melanoma.
*Squamous cell carcinoma(SCC): A 19-year-old with locally advanced periorbital/nasal SCC was treated with cemiplimab following proton beam radiotherapy, with the case literature review concluding that anti-PD-1 monoclonal antibodies may be a promising treatment approach in this genodermatosis.
*Rare tumor types: Even non-standard XP-associated cancers have responded – a case of metastatic cutaneous angiosarcoma in an XP patient, unresponsive to three prior lines of conventional sarcoma therapy, showed a dramatic response to an ICI, guided by whole-genome sequencing that revealed a heavily mutated tumor profile.
*Pediatric cases: A 2025 review of children with XP and advanced cutaneous squamous cell carcinoma concluded anti-PD-1 inhibitors could be highly effective and safe for children with XP and advanced cutaneous squamous cell carcinoma , though it noted that eruptive keratoacanthomas and new squamous cell carcinomas have been documented as adverse cutaneous events during anti-PD-1 therapy, typically manageable with conventional local treatments like intralesional corticosteroids or cryotherapy.References:
1. Response to pembrolizumab in a patient with xeroderma pigmentosum, metastatic cutaneous melanoma and multiple squamous cell carcinomas: a case report. Skin Health and Disease, Oxford Academic. https://academic.oup.com/skinhd/article/5/5/378/8246107
2. Immunotherapy in Xeroderma Pigmentosum: a case of advanced cutaneous squamous cell carcinoma treated with cemiplimab and a literature review. Oncotarget, 2021. https://www.oncotarget.com/article/27966/text/
3. Dramatic response of metastatic cutaneous angiosarcoma to an immune checkpoint inhibitor in a patient with xeroderma pigmentosum: whole-genome sequencing aids treatment decision in end-stage disease. PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC6824248/
4. Gambichler T, et al. Immune checkpoint inhibitors for children with xeroderma pigmentosum and advanced cutaneous squamous cell carcinoma: A case presentation and brief review. JDDG: Journal der Deutschen Dermatologischen Gesellschaft, 2025. https://onlinelibrary.wiley.com/doi/10.1111/ddg.15648
5. Fernandez ER, Tamura D, Khan SG, et al. Retrospective study of efficacy and adverse events of immune checkpoint inhibitors in 22 xeroderma pigmentosum patients with metastatic or unresectable cancers. Frontiers in Oncology, 2023. DOI: 10.3389/fonc.2023.1282823. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10634243/
