What are the possible causes of a platelet count of 137 ×10⁹/L in a 38‑year‑old man with hypertension?

Causes of Platelet Count 137 ×10⁹/L in a 38-Year-Old with Hypertension

A platelet count of 137 ×10⁹/L represents mild thrombocytopenia that does not require immediate intervention in the absence of bleeding symptoms. 1

Initial Assessment: Confirm True Thrombocytopenia

Before pursuing an extensive workup, exclude pseudothrombocytopenia by repeating the platelet count in a heparin or sodium citrate tube, as EDTA-dependent platelet clumping falsely lowers automated counts in approximately 0.1% of adults. 2 Request manual peripheral blood smear review by a hematopathologist to confirm true thrombocytopenia and identify platelet clumping, giant platelets, or other abnormalities. 2

Primary Causes to Consider in This Patient

Medication-Related Causes

• Antihypertensive medications can affect platelet counts, though they more commonly alter platelet function rather than number. 3, 4
• Review all medications including prescription drugs, over-the-counter products, herbal supplements, and quinine-containing beverages, as many agents (sulfonamides, quinidine, heparin, alcohol) can cause thrombocytopenia. 2
• Common drug classes that precipitate thrombocytopenia include antibiotics, anticonvulsants, and non-steroidal anti-inflammatory drugs. 1

Ethnic Variation and Benign Physiological Causes

• Among non-Western ethnic populations, the normal reference range for platelet counts often spans 100-150 ×10⁹/L, representing a benign physiological variation that does not require therapeutic intervention. 1
• In patients whose initial platelet count falls between 100-150 ×10⁹/L, the likelihood of developing a persistent count below 100 ×10⁹/L over a ten-year follow-up period is approximately 6.9%. 1

Hypertension-Related Platelet Changes

• Hypertensive patients demonstrate changes in platelet physiology, including increased platelet volume and mass, though platelet count itself is typically not reduced in essential hypertension. 5, 6
• The increased risk of target organ damage in hypertension relates to platelet activation and prothrombotic state rather than thrombocytopenia. 6

Secondary Immune Thrombocytopenia

• HIV and Hepatitis C testing should be performed in all adults with suspected immune thrombocytopenia, regardless of risk factors, as these infections may be clinically indistinguishable from primary ITP and can precede other symptoms by years. 2
• Autoimmune disorders, common variable immune deficiency, and lymphoproliferative disorders can cause secondary immune thrombocytopenia. 2

Bone Marrow Suppression

• Chronic alcohol use, certain medications, viral infections, and iron overload can suppress bone marrow platelet production. 2
• Bone marrow disorders including myelodysplastic syndromes and leukemias impair megakaryocyte function. 2

Essential Diagnostic Workup

For a 38-year-old with mild thrombocytopenia (137 ×10⁹/L), the following tests are mandatory:

• Complete blood count with differential to confirm isolated thrombocytopenia versus pancytopenia. 2
• Peripheral blood smear review by a hematopathologist to exclude pseudothrombocytopenia, identify giant platelets, schistocytes, or leukocyte abnormalities. 2
• HIV antibody testing – HIV-associated thrombocytopenia can mimic primary ITP and may precede other manifestations. 2
• Hepatitis C virus serology – chronic HCV can cause thrombocytopenia; antiviral cure may resolve the hematologic abnormality. 2
• Comprehensive medication review including all antihypertensive agents, over-the-counter medications, and supplements. 2

Management Approach

Outpatient observation without immediate treatment is appropriate for this asymptomatic patient with a platelet count of 137 ×10⁹/L, provided that hematology follow-up is arranged within 24-72 hours if the thrombocytopenia is newly identified. 7

When Treatment Would Be Indicated:

• Platelet count drops below 30 ×10⁹/L. 1
• Development of mucocutaneous bleeding. 1
• Additional risk factors such as anticoagulant use, upcoming invasive procedures, or advanced age. 1

Activity and Medication Restrictions:

• No activity restrictions are necessary for patients with platelet counts >50 ×10⁹/L. 1
• Full therapeutic anticoagulation can be safely administered with platelet counts >60 ×10⁹/L. 1
• Avoid medications that impair platelet function (aspirin, NSAIDs) if bleeding risk is elevated. 2

Critical Pitfalls to Avoid

• Do not initiate treatment based solely on platelet count; clinical bleeding manifestations and individual risk factors must guide therapy decisions. 7
• Never diagnose ITP without personal review of the peripheral blood smear, as automated counters can miss pseudothrombocytopenia, giant platelets, or schistocytes. 2
• Never omit HIV and HCV testing in adults, because these infections can masquerade as primary ITP. 2
• The presence of splenomegaly, hepatomegaly, or lymphadenopathy rules out primary ITP and should prompt evaluation for HIV, systemic lupus erythematosus, lymphoproliferative disorders, or chronic liver disease. 2

Follow-Up Strategy

Ensure hematology consultation within 24-72 hours for any newly diagnosed thrombocytopenia to reassess the trend and underlying cause. 7 Weekly platelet count monitoring is appropriate for newly diagnosed thrombocytopenia until the trend is established. 1