Determine When to Test for Familial Hyperaldosteronism Type I
STEP 1 — Gather Information
Confirm PA diagnosis via positive ARR and a confirmatory test; record patient's age at PA onset; obtain family history of PA or early-onset stroke (<40 years).
STEP 2 — Rule In / Rule Out
Is PA onset <20 years OR is there a family history of PA or stroke before age 40? If yes, proceed to Step 3; if no, FH-I testing is not routinely indicated.
STEP 3 — Classify or Stratify
Classify as FH-I suspected when either criterion is met; prioritize testing if both early onset and family history are present.
STEP 4 — Decide
Offer genetic testing for the CYP11B1/CYP11B2 chimeric gene (FH-I/GRA) and consider a low-dose glucocorticoid trial to assess biochemical response.
Clinical Guardrails / Mimics / Pitfalls
Do not test for FH-I in PA diagnosed after age 20 without family history; avoid confusing FH-I with FH-II or FH-III, which have different inheritance and glucocorticoid responsiveness; ensure PA is confirmed before genetic workup; note that glucocorticoid suppression can support diagnosis but genetic testing is definitive.
Concrete Clinical Example
An 18‑year‑old with hypertension, spontaneous hypokalemia, ARR 45, and post‑saline infusion PAC 18 ng/dL confirms PA; father had a hemorrhagic stroke at age 38. FH-I suspicion is high, prompting genetic testing for the CYP11B1/CYP11B2 chimera.
Source: The Management of Primary Aldosteronism: Case Detection, Diagnosis, and Treatment: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2016, DOI:10.1210/jc.2015-4061