Probably a silly question on filling out disability claim for secondary condition.

No, you do not need to fill out the toxic exposure section again for your secondary condition claim. The claim for secondary service connection is an entirely separate legal theory from direct service connection under the PACT Act, and its adjudication is governed by different regulations. Your secondary claim relies on establishing a medical nexus between your already-service-connected primary condition (which itself may be connected via toxic exposure) and the new secondary disability, per **38 CFR 3.310(a)**. The key is proving that the secondary condition is "proximately due to or the result of" the primary condition. You must provide a current diagnosis for the secondary condition (Diagnostic Code specific to that condition) and, most critically, a robust medical nexus letter from a physician that explains the etiology, citing medical literature, and states it is "at least as likely as not" (a 50% or greater probability per **38 CFR 4.3**) caused or aggravated by the primary condition. Case law like *Waller v. Wilkie* emphasizes the importance of this medical rationale. Your actionable next steps are: 1) Obtain a formal diagnosis for the secondary condition; 2) Secure a detailed Independent Medical Opinion (IMO)/nexus letter from a treating specialist or retained expert explicitly linking the two conditions; 3) File the claim (VA Form 21-526EZ) clearly stating you are seeking secondary service connection, citing your primary condition's diagnostic code; and 4) Submit all relevant private treatment records alongside the nexus letter. Do not rely on the VA to develop this nexus for you. *Disclaimer: This is educational information regarding VA claims processes and is not intended as legal or medical advice.*