Thrombocytosis
Causes of a High Platelet Count
Elevated platelet counts, or thrombocytosis, can arise from two primary categories:
Primary (Clonal) Causes:
These are less common and originate from bone marrow disorders such as myeloproliferative disorders, including Chronic Myeloid Leukemia (CML).
Secondary (Reactive) Causes:
Blood loss
Iron deficiency
Inflammation, including autoimmune and rheumatological conditions
Infections
Certain solid malignancies (particularly lung, endometrial, gastric, esophageal, and colorectal cancers). LEGO-C
Splenectomy (removal of the spleen)
Recent surgery
Symptoms and Complications
Although a high platelet count might not cause noticeable symptoms, some individuals may experience:
Fatigue
Itching (pruritus)
More importantly, elevated platelet counts can increase the risk of blood clots (thrombosis), which can lead to serious complications such as stroke or heart attack. These complications are likely due to abnormalities in the platelets themselves, rather than just their elevated numbers.
Evaluating and Managing a High Platelet Count
Assess Cancer Risk:
A platelet count exceeding 400 x 10⁹/L in adults over 40 is a significant predictor of a cancer diagnosis within the next year. This finding requires careful evaluation.
Investigate Thoroughly:
Further investigation is essential to determine the underlying cause of thrombocytosis.
Consider Pre-Existing Conditions:
While assessing, consider non-malignant conditions that might contribute to elevated platelet counts, but remain vigilant about the potential for cancer.
Initial Investigations:
In the absence of specific symptoms, initial tests should include basic blood tests, a chest X-ray, and possibly a fecal immunochemical test (FIT) for hidden blood in the stool.
Follow-Up and Referral:
If initial investigations are normal, recheck the platelet count after one month. Persistent or increasing platelet levels should prompt referral for further evaluation.
Physical Examination:
Check for signs of hepatosplenomegaly and lymphadenopathy, which may provide additional clues to the underlying condition.