What workup is indicated for a 66-year-old male with markedly elevated ferritin, normal iron studies, and ankylosing spondylitis treated with secukinumab (Cosentyx)?

Workup for Elevated Ferritin in a Patient with Ankylosing Spondylitis on Secukinumab

In this 66-year-old male with ferritin of 1011 μg/L, normal transferrin saturation, and ankylosing spondylitis treated with Cosentyx, the elevated ferritin most likely represents an acute phase reactant from chronic inflammation rather than true iron overload, and the primary workup should focus on excluding malignancy, infection, and liver disease rather than pursuing hemochromatosis evaluation.

Understanding the Elevated Ferritin in Context

The ferritin level of 1011 μg/L with otherwise normal iron studies (specifically normal transferrin saturation) is a critical distinction. Ferritin can be elevated in the absence of increased iron stores in patients with chronic inflammatory conditions, and in the general population, iron overload is not the most common cause of an elevated ferritin level 1.

In this patient with ankylosing spondylitis, a chronic inflammatory disease, the elevated ferritin is most consistent with inflammation rather than hemochromatosis, particularly given:

• Normal transferrin saturation (the key distinguishing feature) 1
• Chronic inflammatory condition (AS) known to elevate ferritin 1
• Ferritin just above 1000 μg/L threshold 2

Essential Initial Workup

1. Verify Transferrin Saturation is Truly Normal

• Confirm transferrin saturation is <45% on repeat testing 1
• If TS ≥45%, proceed to HFE genotyping for hemochromatosis evaluation 1
• If TS remains <45%, hemochromatosis is unlikely and inflammation is the probable cause 1

2. Assess Liver Function and Exclude Hepatic Disease

• Obtain ALT, AST, and platelet count 1
• A ferritin >1000 μg/L with elevated aminotransferases and platelet count <200 predicts cirrhosis in 80% of hemochromatosis patients, but this patient's normal iron studies make hemochromatosis unlikely 1
• Evaluate for fatty liver disease, alcohol use, and viral hepatitis as alternative causes of hyperferritinemia 1

3. Screen for Malignancy

• Malignancy was the most frequent cause of markedly elevated ferritin (>1000 μg/L) in a large academic center study, accounting for 153 of 627 cases 2
• Age-appropriate cancer screening should be current (colonoscopy, prostate screening) 2
• Consider CBC to exclude hematologic malignancy, particularly lymphoma which commonly elevates ferritin 1, 2

4. Evaluate for Active Infection

• Assess for signs/symptoms of infection, particularly given secukinumab use 3, 4, 5
• Secukinumab increases risk of infections including candidiasis, with pooled incidence of opportunistic infections <0.2/100 patient-years 5
• Consider inflammatory markers (CRP, ESR) to assess disease activity of AS itself 6

When to Pursue Further Iron Overload Evaluation

Liver MRI with R2 quantification should be considered if there is an unclear cause of hyperferritinemia after initial workup* 7. However, this is NOT the first-line test in this patient because:

• Normal transferrin saturation makes HFE hemochromatosis very unlikely 1
• The chronic inflammatory condition (AS) provides a clear alternative explanation 1, 2
• MRI is reserved for patients with biochemical iron overload (elevated TS AND ferritin) or unclear etiology after excluding common causes 7

Specific Considerations for Secukinumab Treatment

The patient's treatment with secukinumab (Cosentyx) for ankylosing spondylitis is relevant but does not directly cause hyperferritinemia 8. However:

• Secukinumab has demonstrated favorable long-term safety with no increase in serious adverse events over 5 years 5
• Active tuberculosis or latent TB infections are rare with secukinumab 5
• The medication itself is not known to cause elevated ferritin 3, 4, 5

Common Pitfalls to Avoid

1. Do not pursue HFE genotyping without elevated transferrin saturation - this leads to unnecessary testing and does not change management when TS is normal 1

2. Do not assume iron overload based on ferritin alone - in patients with chronic inflammatory conditions like AS, ferritin is a nonspecific acute phase reactant 1

3. Do not overlook malignancy - it is the leading cause of markedly elevated ferritin in general medical populations 2

4. Do not order liver biopsy for iron quantification - this is only indicated if there is evidence of cirrhosis or unclear diagnosis after non-invasive testing, and only when true iron overload is suspected 7, 1

Recommended Algorithmic Approach

1. Repeat iron studies (TS, ferritin) to confirm findings 1
2. If TS <45%: Evaluate for secondary causes (liver enzymes, CBC, age-appropriate cancer screening, assess AS disease activity) 1, 2
3. If TS ≥45%: Proceed to HFE genotyping 1
4. If secondary causes identified: Treat underlying condition and monitor ferritin 1, 2
5. If no cause identified and ferritin remains >1000 μg/L: Consider hepatic MRI R2* for iron quantification 7