What are the causes of low platelet count in a patient in their late 80s?

Causes of Low Platelets in Patients in Their Late 80s or Older

In patients aged 80 and above, thrombocytopenia most commonly results from decreased bone marrow production (myelodysplastic syndromes, medications, nutritional deficiencies), increased destruction (immune thrombocytopenia, drug-induced), splenic sequestration (liver disease), or a combination of these mechanisms, with the critical distinction being that older adults have significantly higher rates of secondary causes requiring different treatment approaches than younger patients. 1, 2, 3

Primary Mechanisms in the Elderly Population

Decreased Bone Marrow Production

• Myelodysplastic syndromes (MDS) are the most important consideration in patients over 80 years, as MDS incidence peaks in this age group and can present with isolated thrombocytopenia before other cytopenias develop 1, 2, 3
• Medications causing myeloid toxicity are extremely common in elderly patients, including chronic use of NSAIDs, antibiotics (especially trimethoprim-sulfamethoxazole, vancomycin), antivirals, and cardiovascular medications 1, 2, 4
• Nutritional deficiencies, particularly vitamin B12 and folate deficiency, cause megaloblastic anemia with associated thrombocytopenia and are frequently overlooked in elderly patients with poor dietary intake 2
• Chronic alcohol use suppresses bone marrow platelet production, a common but under-recognized cause in older adults 1, 2
• Viral infections (HIV, hepatitis C, EBV) suppress bone marrow production and may have been present for years before diagnosis 1, 2

Increased Platelet Destruction

• Primary immune thrombocytopenia (ITP) has a second peak incidence after age 60, with the highest rates occurring after age 80 3, 1
• Drug-induced immune thrombocytopenia is more common in elderly patients due to polypharmacy, with typical onset 5-14 days after drug exposure 1, 2
• Heparin-induced thrombocytopenia (HIT) presents 5-10 days after heparin exposure with moderate thrombocytopenia (30,000-70,000/μL) and paradoxical thrombosis risk, requiring immediate 4T score calculation 1, 2
• Secondary immune thrombocytopenia associated with autoimmune diseases, lymphoproliferative disorders, or chronic infections is more prevalent in older adults 1, 2

Splenic Sequestration

• Liver disease with portal hypertension causes intra-splenic platelet sequestration, with thrombocytopenia being the most common hematological manifestation in cirrhosis 2, 5
• Hypersplenism from any cause (including myelofibrosis, lymphoma) sequesters platelets and is more common with advancing age 2

Dilution and Consumption

• Disseminated intravascular coagulation (DIC) from sepsis, malignancy, or trauma causes consumption of platelets through widespread fibrin deposition 6, 2
• Thrombotic microangiopathies (TTP, HUS) cause platelet consumption through microvascular thrombosis and require emergency recognition 1, 2

Critical Age-Specific Considerations

Mandatory Bone Marrow Examination Indications

• Age ≥60 years is an absolute indication for bone marrow examination when evaluating new thrombocytopenia to exclude MDS, leukemia, or other malignancies, regardless of other features 5, 1, 3
• Bone marrow examination must include aspirate, biopsy, flow cytometry, and cytogenetic testing to adequately exclude clonal disorders 5, 1

Polypharmacy Assessment

• Review all medications including over-the-counter drugs and herbal supplements, as drug-induced thrombocytopenia is a leading cause in elderly patients 1, 2, 4
• Common culprits in the elderly include: antibiotics (vancomycin, linezolid, trimethoprim-sulfamethoxazole), cardiovascular drugs (thiazides, furosemide), anticonvulsants, and NSAIDs 1, 2

Infection Screening

• HIV and hepatitis C testing is mandatory in all adults with suspected ITP, as these infections may precede other symptoms by years and require different treatment approaches 5, 1, 2
• H. pylori testing should be performed, as eradication therapy can resolve thrombocytopenia in infected patients 5, 1

Diagnostic Algorithm for Elderly Patients

Step 1: Exclude Pseudothrombocytopenia

• Repeat complete blood count in heparin or sodium citrate tube, as EDTA-dependent platelet clumping falsely lowers automated counts 1, 4
• Request manual peripheral blood smear examination by a hematologist to identify platelet clumping definitively 1

Step 2: Determine Isolated vs. Multi-Lineage Involvement

• Obtain complete blood count with differential to identify isolated thrombocytopenia versus pancytopenia 1, 2, 4
• Pancytopenia mandates immediate bone marrow examination to exclude aplastic anemia, MDS, or leukemia 1, 2

Step 3: Peripheral Blood Smear Review

• Examine for schistocytes (suggests thrombotic microangiopathy), giant platelets (suggests inherited thrombocytopenia), or abnormal white cells (suggests bone marrow disorder) 1, 2
• Evaluate mean platelet volume (MPV): low MPV suggests decreased production (sepsis, marrow hypoplasia, cytotoxic drugs), while high MPV suggests increased destruction (ITP, hyperdestructive causes) 7

Step 4: Mandatory Laboratory Testing

• HIV antibody, hepatitis C antibody (all adults) 5, 1, 2
• Liver function tests, coagulation studies (PT, aPTT, fibrinogen, D-dimer) 5, 1
• Vitamin B12, folate levels 2
• Thyroid function tests (8-14% of ITP patients develop thyroid disease) 2
• H. pylori testing (urea breath test or stool antigen preferred over serology) 1

Step 5: Bone Marrow Examination (Mandatory in Elderly)

• All patients ≥60 years require bone marrow examination to exclude MDS, even with typical ITP features 5, 1, 3
• Include aspirate, biopsy, flow cytometry, and cytogenetics 5, 1

Common Pitfalls in Elderly Patients

• Never diagnose primary ITP without bone marrow examination in patients ≥60 years, as MDS can present identically and requires completely different management 5, 1, 3
• Never skip HIV and HCV testing based on perceived low risk, as these infections can be clinically indistinguishable from primary ITP 5, 1, 2
• Do not overlook medication review, as polypharmacy makes drug-induced thrombocytopenia extremely common in this age group 1, 2, 4
• Recognize that treatment decisions differ in elderly patients due to increased risk of corticosteroid toxicity, bleeding complications, infectious diseases, and thrombosis 3
• Avoid assuming ITP when splenomegaly, hepatomegaly, or lymphadenopathy is present, as these findings exclude primary ITP and mandate investigation for secondary causes 1, 2