Chromogranin A

Chromogranin A (CgA) is a protein stored in secretory granules of neuroendocrine cells — including Mast Cells. It’s released during Degranulation and can be measured in blood as a marker of mast cell activation.

Clinical Use

CgA is included in some broader MCAS diagnostic panels (Consensus-1 criteria). Elevated CgA can support a diagnosis of mast cell activation, particularly when Serum Tryptase is normal.

Important Caveats

CgA is not specific to mast cells. It’s elevated in:

• Proton pump inhibitor (PPI) use — this is the most common cause of falsely elevated CgA
• Neuroendocrine tumors (carcinoid, pheochromocytoma)
• Chronic kidney disease
• Chronic atrophic gastritis
• Heart failure

Any patient on a PPI (omeprazole, pantoprazole, etc.) will likely have elevated CgA regardless of mast cell activity. PPI should be discontinued for at least 2 weeks before testing if the goal is to assess mast cell-related CgA.