Leukocyte abnormalities on blood film inspection

This chapter deals with the various leukocyte abnormalities which have been mentioned in the exam. Thus far these have been limited to toxic changes, immature granulocytosis ("left shift"), band forms and Dohle bodies. The latter only come up only once, in Question 9.3 from the first paper of 2008 - the same question (and the only question) to discuss leukemoid reaction. It is possible that they will never appear again. Leukocyte left shift and toxic changes were mentioned in Question 3.1 from the first paper of 2021, which suggests that the college have not completely forgotten about leukocyte abnormalities. 

Immature granulocytes and band forms

Immature granulocytes are produced in reponse to infection or inflammation, where they are released from the marrow prematurely to compensate for the loss of granulocytes at the front line trenches. Band forms are not synonymous with immature granulocytes, but are used interchangeably. A band cell is an immature neutrophil, but not all immature neutrophils are band cells.  Essentially, a "band cell" features an elongated band-like nucleus, as opposed to a multilobed one. These cells are an intermediate step on the way from myelocyte precursor cells to mature segmented neutrophils. At any given time, one should have no more than 3-5% of one's neutrophils represented by such band forms. If there is any more, that represents a "left shift", a change in the immature:mature ratio.

According to Wikipedia, the term originates from some sort of "left-most button arrangement of early cell sorting machines", where the least mature cells (myeloblasts) were assigned to the left-most button of the manual counter. It's an ancient term, with people in the 1930s already throwing it around as if it were a part of the haematological vernacular. 

The significance and causes of a "left shift "

The following conditions can give rise to an increased proportion of immature neutrophils:

• Sepsis
• Haemorrhage (due to adrenergic mobilisation of marrow neutrophils)
• Necrosis (of any sort, eg. ischaemia)
• Bone marrow infiltration (i.e. insufficient space for proper maturation)
• Anaemia (in an exaggerated haemopoietic reaction, the marrow releases a lot of immature cells, which include neutrophils)

According to a 1997 article by Seebach et al, the utility of this finding in discriminating infectious from non-infectious causes of SIRS is poorer than neutrophil inclusion bodies (such as toxic granules). However, interest in using this parameter in discriminating sepsis from SIRS is still alive (Nierhaus et al, 2013).

Leukoerythroblastic reaction

This had appeared in Question 3.2 from the second paper of 2016. The question expected the candidates to recognise the phenomenon from a blood film with "nucleated red blood cells, immature granulocytes and band forms observed." Four causes were asked for. There are many more than that, but boradly speaking anything which makles the marrow work harder could potentially promote this appearance.

The best source for this is probably the classic 1974 article by Weick et al, but it is not available for the casual Google user. Weick and colleagues reported on a case series of 215 patients with this sort of picture. Of them, the majority (136) had some sort of malignant disease, and the others were either septic or bleeding tod eath (typically from the GI tract). Subsequently, people have published on the finding of leukoerythroblastosis in almost every situation, ranging from pregnancy to the use of granulocyte stimulators.

In summary, the possible causes of leukoerythroblastosis are:

• Bone marrow inflitration ("myelophthisis")
  • Leukaemia
  • Myelofibrosis
  • Solid tumour infiltration, eg. breast cancer
  • Miliary tuberculosis
• Extramedullary haematopoiesis
• States of widespread bone marrow activation
  • Sepsis
  • Inflammatory states, eg. autoimmune disease
  • Severe haemorrhage or haemolysis
  • Use of GM-CSF
  • Marrow recovery following marrow suppression
• Exotic stuff
  • Still disease
  • Gaucher's disease
  • Myocardial infarction
  • Chronic lung diseases

"Toxic changes"

To call "toxic changes" on a blood film, the laboratory scientist needs to find at least two out of three of the following morphological changes:

• Toxic granulation
• Toxic vacuolation
• Döhle bodies

Toxic granulation is the continued presence of dense dark blue-black peroxidase positive granules in the cytoplasm of neutrophils, usually associated with systemic infection or inflammation.  These are basically normal neutrophil granules which have dropped out of school - the normal maturation process is interrupted, presumably by the rushed neutrophil production of the systemic inflammatory response, and the granules retain some of the "acid mucosubstance" which is supposed to disappear with maturation (Schofield et al, 1983). They are thought to be functionally the same as the normal variety of neutrophil granules, i.e. full of various proteolytic inflammatory and bactericidal substances. Though the term "toxic" has all sorts of pejorative connotations, these granules can also be present in pregnancy, following GM-CSF administration, in situations where the bone marrow is recovering from a period of myelosuppression, or with end stage renal failure. A more politically correct non-threatening term would be "azurophilic granules".

Toxic vacuolation is the formation of vacuoles in neutrophils, who are not usually expected to have vacuoles (ergo, all neutrophil vacuoles are toxic vacuoles). These are usually a sign that phagocytosis is taking place. Zieve et al (1966) has some nice black and white microphotographs of such neutrophils; the vacuoles are not subtle (the whole cell body is afroth with them). These vacuoles, if scrutinised more closely, will usually have residual bacterial fragments and lytic enzymes in them. This finding often appears wherever there is bacteremia, i.e the neutrophils are vacuolated because they are involved in phagocytosis directly in the bloodstream. 

Döhle bodies, little peripheral cytoplasmic inclusion bodies in the cytoplasm of neutrophils are thought to be the remnants of the rough endoplasmic reticulum. They appear during leukemoid reactions, but they are also a feature of severe inflammatory states, and are generally considered to be a part of the "toxic" reaction to infection.

The following are scenarios in which one would not be surprised to see some Döhle bodies:

• Syphilis
• Typhoid
• Tuberculosis
• Sepsis
• Severe burns
• Leukemoid reaction
• May-Hegglin disease, a familial disorder also associated with abnormally large platelets

If one is for some reason interested in this blood film abnormality, one may pursue it further, knowing well that doing so imperils their time-critical exam preparation. The topic of neutrophil inclusion bodies is so esoteric that there is very little literature published on the subject, and pragmatic exam-oriented sites like LITFL dedicate an appropriately small amount of space to them.  An excellent article about these little lumps was written by Weiner and Topley in 1955. The bodies were fist discovered in 1911. At first Döhle mistook them for spirochaetes, because the cause of syphilis was only recently discovered with great fanfare,  and everybody was seeing spirochaetes everywhere.