What Does a Ceruloplasmin of 19 mg/dL Mean in Transaminitis?
A ceruloplasmin level of 19 mg/dL in a patient with transaminitis is modestly subnormal and requires further evaluation for Wilson disease, though it does not definitively confirm or exclude the diagnosis. 1
Interpretation of This Specific Value
Your patient's ceruloplasmin of 19 mg/dL falls just below the normal threshold of 20 mg/dL, placing them in a diagnostic gray zone that demands additional workup 1, 2
This level is NOT extremely low (which would be <5 mg/dL), so it does not provide strong evidence for Wilson disease on its own 1, 3
Approximately 10-20% of Wilson disease patients actually have ceruloplasmin levels in the normal range (≥20 mg/dL), and conversely, about 20% of heterozygous carriers have decreased levels, creating significant diagnostic overlap 1
Critical Next Steps You Must Take
Calculate the non-ceruloplasmin bound (free) copper immediately:
- Formula: Serum copper (μg/dL) - [3 × ceruloplasmin (mg/dL)] 1, 4
- For your patient: Serum copper - [3 × 19] = Serum copper - 57
- Free copper >25 μg/dL suggests Wilson disease 1, 4
Obtain 24-hour urinary copper excretion:
Arrange slit-lamp examination for Kayser-Fleischer rings:
- Their presence strongly supports Wilson disease, though absence does not exclude it (especially in purely hepatic presentations) 1, 4
Consider liver biopsy with quantitative copper measurement:
- Hepatic copper >250 μg/g dry weight confirms Wilson disease 2
Common Pitfalls to Avoid
Do not assume this borderline low ceruloplasmin automatically means Wilson disease:
- In one screening study of 2,867 patients with liver disease, only 5.9% of those with ceruloplasmin <20 mg/dL actually had Wilson disease 5
- The positive predictive value of low ceruloplasmin alone is only 11.1% in unselected populations 6
Other causes of modestly low ceruloplasmin in the setting of transaminitis include:
- Heterozygous carrier status for Wilson disease (20% have low levels) 1
- Severe end-stage liver disease from any cause 3
- Protein-losing conditions 3
- Copper deficiency 3
- Alcoholic liver disease (can decrease ceruloplasmin activity) 7
Do not be falsely reassured by this "almost normal" value:
- Up to 22% of confirmed Wilson disease patients had ceruloplasmin ≥17 mg/dL in published series 1
- In pediatric Wilson disease, 10 of 28 children had ceruloplasmin ≥20 mg/dL 1
Why This Matters for Morbidity and Mortality
Missing Wilson disease has catastrophic consequences:
- Untreated Wilson disease progresses to cirrhosis, neurological degeneration, and death 2
- Early treatment with chelation therapy (D-penicillamine or trientine) can prevent disease progression and prolong life indefinitely 3, 2
The diagnostic workup must be completed even with this borderline value because the stakes of missing Wilson disease far outweigh the cost and inconvenience of additional testing 1, 3