Short answer
TSC1/TSC2 genetic testing looks for pathogenic variants linked to tuberous sclerosis complex (TSC), a condition that can affect the brain, skin, kidneys, heart, lungs, and neurodevelopment. It is most useful when the clinical picture already suggests TSC or when a known family variant is being checked in relatives. A negative blood test does not always settle the question because mosaicism can hide a variant in blood.
What testing can clarify
| Situation | What testing can answer | Why it matters |
|---|---|---|
| One or more major TSC features | Can TSC1 or TSC2 confirm the diagnosis? | A molecular diagnosis can support surveillance and family testing. |
| Known family pathogenic variant | Should a relative have targeted testing? | Targeted testing is clearer than broad panel guessing. |
| Clinical concern but negative blood test | Could mosaicism or a different specimen matter? | Blood can miss low-level or tissue-limited variants. |
When testing helps
- When a child or adult already has TSC-type skin, kidney, brain, or seizure findings.
- When a family member has a known pathogenic TSC1 or TSC2 variant and relatives need cascade testing.
- When the result will change follow-up imaging, kidney monitoring, lung screening, or counseling about recurrence risk.
- When mosaicism is on the table and the clinician may want testing beyond standard blood analysis.
When a negative result does not settle the diagnosis
- Low-level mosaicism may not show up in blood at all, or may sit below the assay threshold.
- Some older or narrower assays can miss deletion/duplication changes or complex variants.
- Clinical TSC criteria still matter even if the first blood test is negative.
- When the phenotype is strong, a genetics team may consider deeper analysis or another tissue.
Why screening matters
| Area | Typical follow-up after TSC is diagnosed |
|---|---|
| Brain | Brain MRI and seizure follow-up for cortical tubers, subependymal nodules, or SEGA risk. |
| Kidneys | Kidney imaging and kidney function monitoring for angiomyolipomas and cystic disease. |
| Lungs | Adult lung symptom review, especially for LAM risk in women and people with respiratory symptoms. |
| Skin, eyes, heart | Dermatology, eye, and cardiac follow-up when clinical features point that way. |
What follow-up may include
Follow-up for tuberous sclerosis complex often includes kidney, brain, lung, dermatology, and family surveillance questions, because the result can change care across several organ systems. Genetics review can help map those next steps into a concrete plan.
Questions to ask
- Did the lab sequence both TSC1 and TSC2 and include deletion/duplication analysis?
- Was mosaicism considered, and does the lab have a way to detect low-level variants?
- Is the result pathogenic, likely pathogenic, uncertain, or negative?
- Does the clinical picture still meet TSC criteria despite the result?
- What imaging or specialty follow-up should happen next if the test is positive or unclear?
FAQ
- What genes are usually tested for TSC?
- Most testing starts with TSC1 and TSC2, often with sequencing plus deletion/duplication analysis.
- Does a negative blood test rule out TSC?
- No. A negative blood test does not fully exclude TSC, especially if mosaicism or a tissue-limited variant is possible.
- Why does mosaicism matter?
- Mosaicism means not every cell carries the same variant, so blood can miss the change even when the diagnosis is real.
- What screening may follow a positive result?
- Brain, kidney, skin, eye, heart, and lung follow-up may be considered depending on age and symptoms.
- Should siblings or children be tested?
- If a pathogenic family variant is known, targeted cascade testing can identify relatives who need earlier screening.
- Is TSC just a skin condition?
- No. Skin findings are common, but TSC can also involve seizures, brain lesions, kidney angiomyolipomas, and adult lung disease.
Bottom line: TSC1/TSC2 testing is most useful when it is paired with clinical criteria, mosaicism awareness, and a real surveillance plan.