Can prurigo nodularis be a paraneoplastic manifestation?

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I read your query and can understand your concern.

Prurigo nodularis (PN) is a chronic, intensely itchy skin condition, and while it is often linked to neurologic, inflammatory, or metabolic conditions, it can rarely be a sign of an underlying malignancy, particularly as a paraneoplastic syndrome. Your dermatologist’s concern based on abnormal blood tests is valid, and further evaluation is necessary.

How often is prurigo nodularis a paraneoplastic syndrome?

While most cases of PN are not linked to cancer, studies suggest five to ten percent of cases may have an underlying malignancy, especially in patients who have sudden onset of widespread. Severe PN without a clear cause can occur in people who are older (50+ years old) without a history of chronic skin conditions and have abnormal laboratory findings (for example., unexplained anemia, abnormal white blood cell counts, elevated inflammatory markers).

Cancers are most commonly associated with prurigo nodularis.

If PN is linked to paraneoplastic syndrome, the most commonly associated cancers include:

1. Hematologic malignancies (most common).

2. Lymphomas (Hodgkin’s and non-Hodgkin’s).

3. Leukemia (especially chronic lymphocytic leukemia).

4. Multiple myeloma.

5. Solid organ cancers (less common but possible).

6. Lung cancer.

7. Gastrointestinal cancers (colon, stomach, pancreas).

8. Liver cancer.

9. Kidney cancer.

Further testing to rule out malignancy.

Given your dermatologist's suspicion, the following tests might be recommended such as:

1. Basic blood work and tumor markers.

2. Complete blood count (CBC) to check for anemia, leukocytosis, or thrombocytosis. Liver and kidney function tests to assess liver or kidney involvement.

3. Serum protein electrophoresis (SPEP/UPEP) screen for multiple myeloma.

4. LDH (lactate dehydrogenase) can be seen elevated in lymphomas or leukemia.

5. Beta-2 Microglobulin has to be done if multiple myeloma or lymphoma is suspected.

Imaging tests such as:

1. Chest X-ray or CT (computed tomography) has to be done to check for lung cancer or lymphoma.

2. Abdominal and pelvic CT or MRI (magnetic resonance imaging) have to be done to rule out GI (gastrointestinal tract), kidney, or liver cancers.

3. PET-CT (positron emitted tomography scan with computed tomography) scan has to be done if there is a strong suspicion of malignancy but there is no clear primary site.

Other tests include a bone marrow biopsy that can be done if blood abnormalities suggest leukemia, lymphoma, or multiple myeloma.

If no cancer is found, how should treatment differ?

If malignancy is ruled out, your PN treatment will focus on controlling inflammation, reducing itch, and treating underlying triggers like diabetes, liver disease, or neuropathy.

1. Topical therapies like strong steroids (Clobetasol) or calcineurin inhibitors (Tacrolimus, Pimecrolimus), cryotherapy, or laser therapy for resistant nodules can be taken.

2. For systemic treatments (for widespread or severe PN), biologics like Dupixent (Dupilumab) have shown effectiveness in refractory PN, and JAK inhibitors like Upadacitinib and Baricitinib are used.

3. Thalidomide or Lenalidomide is used in PN associated with hematologic disorders.

4. Immunosuppressants like Methotrexate, Cyclosporine (in severe cases) and neuro-modulators like Gabapentin, and Pregabalin are used for neuropathic itch, and biological therapies or targeted treatments for paraneoplastic PN are taken.

5. If PN is found to be cancer-associated, treating the cancer is the best approach to resolving symptoms. However, if PN persists after cancer treatment, biologics like Dupixent (Dupilumab) or JAK (Janus kinase inhibitors) inhibitors may still be useful.

I hope this answers your query.

Please let me know if I can assist you further.

Thank you.