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September 2014 - Test your knowledge in the quiz below!

Can you provide a diagnosis using these XN results? Malaria tropica infection
Myelodysplastic syndrome (MDS)
Thrombotic thrombocytopenic purpura (TTP)

Online version of this month`s case:


Thrombotic thrombocytopenic purpura (TTP)

Scattergrams and microscopy

Patient history: a 25-year old woman with an unclear anaemia and thrombocytopenia

The WDF scattergram showed the presence of immature granulocytes (IG).
The presence of nucleated red blood cells (NRBC) was detected in the WNR scattergram.
The WPC scattergram showed the absence of abnormal cells.
Blasts were not detected in the SSC-FSC scattergram of the WPC channel.
An increased reticulocyte population and red blood cell fragments (FRC) were visible in the RET scattergram. This triggered the appearance of the flags ‘Reticulocytosis’ and ‘Fragments?’.
Peripheral blood smear


Interpretation and Differential Diagnosis

The answer can be inferred from…


Case history

A 25-year old woman went to the hospital because of fatigue, a fever (38.5°C), pain when moving her wrists and elbows, pallor and a severe headache. Blood analysis showed an extreme thrombocytopenia (12,000/μL), anaemia, reticulocytosis, as well as the presence of fragmented red blood cells, nucleated red blood cells and immature granulocytes. Such an extreme thrombocytopenia is an emergency condition and requires immediate intervention. A decision whether to give a platelet transfusion or a plasma exchange had to be made quickly. In case of thrombotic thrombocytopenic purpura (TTP), a prompt plasma exchange is required to save patient’s life.

Case results

Leukocyte counts were normal and reactive lymphocytes, abnormal lymphocytes or blasts were not found (absence of ‘Atypical Lympho?’, ‘Abn Lympho?’ or ‘Blasts?’ flags), indicating normal leukopoiesis. In addition, NEUT-SSC was normal indicating the absence of neutrophil dysplasia. However, the increased IG counts suggested bone marrow stimulation either by leukaemic bone marrow infiltration, inflammation or infection. These conditions could also be responsible for the observed extreme thrombocytopenia (PLT = 12,000/μL). The presence of NRBC in the peripheral blood indicated bone marrow activation and indeed reticulocytosis was increased (high RET#, RET%, IRF). Fragmented red blood cells were detected (FRC#, FRC%; ‘Fragments?’ flag), and confirmed in the peripheral blood smear, visible as tapered and hornlike ‘helmet’ cells. The presence of RBC fragments and enhanced erythropoiesis suggest microangiopathic haemolytic anaemia (MAHA), which could be caused by a number of conditions: thrombotic thrombocytopenic purpura (TTP), haemolytic-uremic syndrome, and pre-eclampsia. Other signs of haemolysis were also present (elevated unconjugated bilirubin and LDH), but they are non-specific.

The presence of enhanced effective erythropoiesis with RBC fragments, extreme thrombocytopenia, normal WBC counts and low levels of ADAMS13 enzyme led to a TTP diagnosis. The increased IG count may be caused by an accompanying inflammation process, bone marrow stimulation or an infection, which was not clear in this case. 

The following answers are incorrect for the described reasons.


Osteomyelofibrosis is a type of a myeloproliferative disorder, where fibrous tissue gradually replaces bone marrow. This occurs due to an abnormal stem cell clone, which by overproduction of cytokines stimulates activity of fibroblasts in the bone marrow. As the marrow is replaced by collagen fibers, haematopoietic stem cells migrate into the liver and spleen (extramedullary haematopoiesis), resulting in a progressive pancytopenia. Patients are usually over 50 years of age and present with the following symptoms: fatigue, weight loss, anaemia, abdominal pain due to splenomegaly and an enlarged liver. The peripheral blood smear appears abnormal with a high proportion of immature myeloid cells and basophils, the presence of nucleated red blood cells and tear-drop shaped RBC. Most patients develop thrombocytopenia. In this case osteomyelofibrosis may be ruled out due to the normal absolute counts of WBC populations, absence of blasts, reticulocytosis, presence of RBC fragments and the young age of the patient (1,2).


Myelodysplastic syndrome (MDS)

The myelodysplastic syndromes (MDS) comprise a heterogeneous group of malignant haematopoietic stem cell disorders characterized by dysplastic and ineffective blood cell production. The symptoms of MDS are often unspecific and depend on the blood and bone marrow cell types which are affected. Most patients suffer from a multilineage dysplasia, and common symptoms include anaemia, pallor, fatigue due to ineffective erythropoiesis, petechia and bruising (as a result of ineffective megakaryopoiesis and thrombocytopenia), and frequent infections due to dysplasia in the neutrophilic lineage and neutropenia. Anaemia is usually macrocytic or normocytic, and the number of reticulocytes is low. Blasts and NRBC may be present in the peripheral blood smear. MDS is unlikely in this case because of the observed reticulocytosis, normal WBC count, absence of neutrophil dysplasia (normal NEUT-SSC) and young age of the patient. MDS also cannot explain the observed haemolysis (3-5).


Malaria tropica infection

Malaria tropica is caused by the parasitic protozoan Plasmodium falciparum, and infection occurs through a bite of a female mosquito carrying the parasite. Malaria tropica is the most severe form of the disease with the highest mortality rate and serious complications. The general symptoms are fever, chills, headache, muscle pain and skin rash. Anaemia due to haemolysis of red blood cells and thrombocytopenia are very common in malaria patients. Malaria is usually confirmed by the microscopic examination of blood films or by antigen-based rapid diagnostic tests. Unlike many cases of the other types of malaria caused by four other Plasmodium species, malaria caused by P. falciparum infection cannot be detected in the WDF scattergram and often does not affect the WBC differential count. Absolute reticulocytosis is characteristic for malaria, while the immature reticulocyte fraction (IRF) is usually low.

Malaria is accompanied by a moderate thrombocytopenia and signs of extramedullar haemolysis, such as increased LDH, but no fragments are observed. In this case we can rule out malaria tropica because of the high IRF, and the presence of RBC fragments and NRBC, both of which are not typical for malaria (6-7).

Underlying Disease

TTP is an uncommon haematologic disorder which is characterised by thrombus formation in most organs caused by spontaneous aggregation of platelets and activation of coagulation. The presence of these thrombi leads to haemolysis in small blood vessels (microangiopathic haemolytic anaemia, MAHA) resulting in serious organ damage such as kidney failure in the worst cases. TTP is usually caused by a lack or deficiency of the zinc-containing metalloprotease enzyme ADAMTS13, which cleaves multimers of von Willebrand factor in the peripheral vasculature. Accumulation of the uncleaved multimers leads to spontaneous aggregation of platelets, activation of coagulation and clot formation. When red blood cells pass areas with blood clots, they are sheared by the accumulated fibrin mesh or damaged by the turbulences in the circulation, producing cell remnants that appear as helmets or other odd shapes when viewed under the microscope. Although ADAMTS13 levels can be measured, the results are often not available at the time of diagnosis. The diagnosis is therefore typically based on clinical symptoms and blood tests, e.g. the presence of typical ’helmet cells‘ in the blood film, thrombocytopenia, haemolytic anaemia, reticulocytosis, fragmented red cells and increased LDH. A clinical triad of thrombocytopenia, red blood cell fragments (schistocytosis), and an increased lactate dehydrogenase (LDH) level is enough to suggest the diagnosis.

TTP can be familial or acquired. Familial TTP manifests in infancy or childhood, and often remits and relapses. Patients experience cyclic episodes of thrombocytopenia and haemolysis every 21 to 30 days. In familial, or congenital TTP, deficiency of ADAMTS13 occurs through lower production rate of this enzyme or production of inactive forms due to genetic mutations. Acquired TTP is more common and manifests in adults or older children and often occurs as a single acute episode. The levels of ADAMTS13 are usually higher in acquired than in congenital TTP, and the deficient activity is explained by the presence of auto-antibodies against this enzyme.

Untreated TTP has a mortality rate of 90%. Even with current treatment regimens, the mortality rate remains at 10% to 20%. Most TTP-associated deaths occur within the first 48 hours of presentation, emphasizing the need for early recognition.
The treatment of childhood TTP involves the transfusion of platelet-poor fresh-frozen plasma or cryoprecipitate-poor plasma every 3 weeks. The treatment of adults or older children with acquired TTP is by daily plasma exchange until platelet counts and LDH levels normalize.  Patients not responding to these modalities might require additional treatment with steroids, splenectomy, or administration of vincristine or retuximab. Platelets should not be transfused unless a life-threatening haemorrhage or intracranial bleeding is present (8-12).

RBC fragments (FRC)

The arrows in Figure 1 point to fragmented RBC, that are morphologically called helmet cells. These cells are usually caused by some type of mechanical damage. The helmet cell has 2 projections on either end that are tapered and hornlike. Fragmentation of the red blood cells occurs when they pass through areas of thrombi (masses or clots) or due to turbulence in the circulation. Such forces shear the cells, producing cell remnants that appear as helmets and other odd shapes when viewed under a microscope. The diagnosis of TTP is assisted by the microscopic examination of the blood for such sheared red blood cells.


Nucleated red blood cells (NRBC)

NRBC are seen as a reflection of extreme increases in erythropoietic activity, such as in acute haemolytic episodes and severe hypoxic stress, or as a result of a haematological malignancy. This includes many leukaemias and myelodysplastic syndromes, and some kinds of lymphoma. NRBC can also be present in thalassaemia syndromes, bone marrow metastases of solid tumours, extramedullary haematopoiesis and other conditions of haematopoietic stress such as sepsis, or massive haemorrhages. In these situations, their presence is correlated with the severity of the disease. It has been observed that the entity and duration of the presence of NRBC in peripheral blood is associated with a poor prognosis in several haematological and non-haematological diseases. The identification of blood-circulating NRBC provides important clinical clues in:

  • Para-physiologic states of premature babies
  • Conditions of intense erythropoietic activity (e.g. immune haemolytic anaemia, haemolytic crisis in congenital anaemias, microangiopathic anaemia, severe thalassaemia or sickle cell anaemia, recovery from aplasia or bone marrow transplantation)
  • Severe disorders of haematopoiesis (e.g. infiltration by tumour cells, lymphoma or leukaemia; fibrosis and extramedullary haematopoiesis)
  • Hypoxic states (e.g. severe haemorrhages, cardiac and pulmonary disorders, foetal asphyxia)
  • Other conditions of haematopoietic stress such as sepsis
Figure 1: Fragmentation of erythrocytes (helmet cells)


  1. Mascarenhas JO, Orazi A, Bhalla KN et al. (2013): Advances in myelofibrosis: a clinical case approach. Haematologica 98(10):1499-509
  2. Savona MR (2014): Are we altering the natural history of primary myelofibrosis? Leuk Res. Epub ahead of print. PMID:24931396
  3. Swerdlow SH, Campo E, Harris NL, et al. (2008):  WHO classification of Tumors of Haematopoietic and Lymphoid Tissues, IARC Press, Lyon
  4. Barzi A, Sekeres MA (2010): Myelodisplastic syndromes: a practical approach to diagnosis and treatment. Cleve Clin J Med. 77(1):37-44
  5. Bowen D, Culligan D, Jowitt S, et al.(2003): Guidelines for the diagnosis and therapy of adult myelodysplastic syndromes. Br J Haematol. 120:187 
  6. Akinosoglou KS, Solomou EE, Gogos CA. (2012). Malaria: a haematological disease. Hematology 17(2):106-14
  7. Campuzano-Zuluaga G, Hänscheid T, Grobusch MP (2010): Automated haematology analysis to diagnose malaria. Malar J. 30;9:346
  8. Sawyer NA (2010): TTP’s toll. Confronting a diagnostic challenge in the ED. Adv NPs Pas.1(1):37-9
  9. Sadler JE (2008): Von Willebrand factor, ADAMTS13, and thrombotic thrombocytopenic purpura. Blood 112(1):11-8
  10. Moake JL (2002): Thrombotic microangiopathies. N Engl J Med. 347:589-600.
  11. Thrombocytopenia. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011: chap 175.
  12. Thrombotic thrombocytopenic purpura (TTP) and hemolytic-uremic syndrome. The Merck Manuals: The Merck Manual for Healthcare Professionals.

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