A Quick Synopsis of " Thrombocytopenia"

Thrombocytopenia
ROBERT L. GAUER, MD, Womack Army Medical Center Family Medicine Residency, Fort Bragg, North Carolina
MICHAEL M. BRAUN, DO, 1st Special Forces Group, Fort Lewis, Washington
Am Fam Physician. 2012 Mar 15;85(6):612-622.
http://www.aafp.org/afp/2012/0315/p612.pdf

     Thrombocytopenia is a low platelet count (less than 150). Patients with platelet counts above 50 are usually asymptomatic.  Those less than 50 may begin to see bleeding with trauma. Those less than 30 may have spontaneous bleeding, petechiae, and bruising.
    There are three primary causes of thrombocytopenia. Decreased platelet production (1) can be do to bone marrow problems, alcohol, infection, B12/ folate deficiency, or "congenital macrothrombocytopenias" such as Alport's, Wiskott-Aldrich, Bernard-Soulier, or Fanconi. Increased platelet consumption (2) can be due to autoimmune syndromes (SLE, sarcoidosis, antiphospholipid syndrome), DIC, HIT, ITP, infection, HELLP/preeclampsia, TTP, or HUS. Platelet sequestration (3) can be due to alcohol, liver disease, PE, pulmonary hypertension, or gestational thrombocytopenia.
   A peripheral blood smear is very helpful when making a diagnosis. Atypical lymphocytes may be due to a viral infection. Basophilic stippling may be due to thalassemia, alcohol, or lead poisoning. Cryoglobulin may be due to cryoglobulinemia, multiple myeloma, or mycoplasma pneumonia. Giant platelets may be due to ITP or congenital thrombocytopenias. Megakaryocyte fragments may be due to myelofibrosis. Nucleated RBC's may be due to myelofibrosis or hemolysis. Oval macrocytes may be due to B12 or folate deficiencies. Platelet agglutination may be due to pseudothrombocytopenia. Schistocytes may be due to TTP, HUS. DIC, or a defective prosthetic heart. Target cells may be due to chronic liver disease or hemoglobinopathies. I kinda stole this right from Table 4 of this article.
     ITP will oftentimes resolve spontaneously in children. Adults are at a higher risk of bleeding. Secondary ITP is associated with autoimmune disorders, lymphoproliferative disorders, and infections. Almost half of these patients will test positive for ANA and antiphospholipid antibodies (without having the corresponding disease). First line treatment is corticosteroids, immunoglobulin, or rituximab. Second line treatment is thrombopoietin receptor agonists or splenectomy.
     HIT takes about 5-10 days to show a drop in platelet count in patients naive to heparin, but in can drop in hours for those who have had previous heparin exposure.  HIT can be complicated by thrombosis, even after heparin is stopped. Features of HIT include skin necrosis, DVT, PE, stroke, or MI. Testing includes EIA of platelet factor 4/anion complex. By the way, stop the heparin!
     TTP has a clinical pentad. "Klmno" is the mnemonic that I use. It stands for kidneys, low grade fever, microangiopathic hemolytic anemia, neurologic signs, and thrombOcytopenia. It can lead to ischemia and necrosis, and seen mostly in adults. Treatment is plasma exchange.
     HUS is a child version of TTP. It presents with acute renal failure and bloody diarrhea. It is caused by a shiga toxin from E. coli.
     Preeclampsia and HELLP syndrome may have symptoms of thrombocytopenia, headache, vision problems, RUQ pain, hypertension, anemia, elevated liver enzymes, elevated lactate dehydrogenase, and proteinuria, at 20 weeks of gestation. Treatment consists of magnesium.
     Drug induced thrombocytopenia is a common cause of acute platelet drops. It usually takes about 5-7 days for it to occur, with resolution in 1-2 weeks. Medications include, but are not limited to abciximab, carbamazepine, cephalosporins, cimetidine, heparin, HCTZ, interferon, MMR, phenytoin, quinidine, rifampin, TMP/SMX, and vancomycin.
     Some of the infections that can cause thrombocytopenia include hepatitis B and C, HIV, EBV, CMV, parvovirus, VZV, rubella, mumps, malaria, dengue fever, typhoid fever, lyme disease, RMSF, and ehrlichiosis. Liver disease can also be the cause.
     Gestational thrombocytopenia is a benign diagnosis, thought to be caused by hemodilution or accelerated platelet clearance. Mild ITP during pregnancy may mimic gestational thrombocytopenia ,so the platelet count should be watched.
    Thrombocytopenia should be considered when making recommendations about patient activity, especially in contact sports.