A 16-year-old male presents with a nagging, worsening cough that has been present for 4 weeks. His blood smear is shown here. What is the diagnosis?
A. Bordetella pertussis
B. Streptococcus pharyngitis
C. Mycoplasma pneumoniae
D. Respiratory syncytial virus
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(Scroll down for the answer)
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The answer is A, Bordetella pertussis infection. Bordetella pertussis infection is one of only two infectious diseases (the other is infectious lymphocytosis) that manifests in the blood as a mature lymphocytosis. A “mature” lymphocytosis is one in which the cells appear relatively small, with condensed chromatin, and no unusual reactive changes – basically, they look like regular old mature lymphocytes.
If you see a mature lymphocytosis in an adult, by the way, you need to rule out chronic lymphocytic leukemia, which can look very similar to a benign, mature lymphocytosis. In fact, you really can’t tell the two apart reliably just by looking at a blood smear. You need to do flow cytometry to be sure. In CLL, the cells are positive for B cell markers but also positive for CD5. In a benign lymphocytosis, the cells would be a mixture of B and T cells – and you wouldn’t see that CD5 marker on the B cells. CLL doesn’t occur in kids – so it’s not a consideration in this patient.
Back to our case. We talked about a mature lymphocytosis, which is what you see in Bordetella pertussis infection and in infectious lymphocytosis. Other viral infections lead to a “reactive” lymphocytosis. In this type of lymphocytosis, the lymphocytes don’t look small and mature. They tend to look weird – they have voluminous cytoplasm, for example, or large nuclei with fine chromatin and nucleoli.
There’s one other clue to Bordetella that people don’t talk about much, but it’s pretty cool. In Bordetella, the lymphocytes often have a weird clefted appearance. There are several clefted lymphocytes in the slide above. Here are two of them up close:
This is a good little finding to tuck in the back of your brain. If you see it, and you diagnose Bordetella from the blood smear, people will think you’re a genius!
If you liked this case, and want to test yourself with other unknown cases, here are some to try:
- Case 1: 20-year-old male who died suddenly
- Case 2: 72-year-old male with right calf mass
- Case 3: 67-year-old female with pancytopenia
- Case 4: 59-year-old male with severe headaches
- Case 5: 38-year-old female with deep venous thrombi
- Case 6: 13-year-old male with cerebellar mass
- Case 7: 45-year-old male with pulmonary emphysema
- Case 8: 38-year-old male with AIDS and headaches
- Case 9: 25-year-old male with arm mass
- Case 10: 57-year-old male with fatigue and left upper quadrant heaviness
- Case 11: 62-year-old male with hepatosplenomegaly, skin lesions and cardiomyopathy
- Case 12: 16-month-old infant with failure to thrive
- Case 13: 36-year-old female with painless lower leg nodule
- Case 14: 58-year-old female with several-year history of pelvic pain
- Case 15: 52-year-old male with abdominal pain and bloody diarrhea
- Case 16: 42-year-old female with tinnitus, hearing loss, and a mass at the cerebellopontine angle
- Case 17: 52-year-old male with HIV with profuse, watery diarrhea
- Case 18: 44-year-old male with history of progressive weakness and visual changes
- Case 19: 20-year-old male with large, deep thigh mass
- Case 20: 60-year-old male with multiple lung nodules
- Case 21: 3-year-old boy with 7 cm abdominal mass
- Case 22: 15-year-old male with large thigh mass
- Case 23: 7-year-old male with headache, vomiting and gait ataxia
Great thx…
Great case, but why do you say they are not reactive? Talking about the lymphocytes in the picture. They are bigger than normal , I can see at least two nucleoli and the way they ”surround” erythrocytes is typical of reactive lymphocytes.
Whats the difference between mature lymphocytes and atypical lymphocytes
Interesting n informative too
I thought these cells were monocytes!!?
Your description is great – and you’re right – they do look reactive in this photo! I wish I had a better case of Bordetella with clefted nuclei in which the lymphocytes look more mature. We do classify Bordetella infections under the “mature lymphocytosis” category – and usually they do look a little more mature than they did in this case. Sometimes real life doesn’t match the photos very well – and sometimes something as simple as a different lab’s blood staining procedure can make a huge difference. So: you’re right – they do look more reactive than usual in this case.
Mature lymphocytes look like your regular old lymphocytes that you see in the blood every day. Atypical lymphocytes look different – and there are many ways they can look different! One of the most common is the so-called “fried egg” cell that you see in infectious mono. It has a TON of cytoplasm, a fairly fine chromatin pattern, and it reaches out to touch the red cells around it. The cytoplasm condenses in little rays. Very pretty. There are a lot of different ways atypical lymphocytes can appear – but the main thing is, they look different than the normal lymphs you see in the blood.
They do kind of look like monocytes! Others have commented that these cells look more “atypical” than “mature” – and that is true in this particular case. They are larger than you’d expect in a mature lymphocytosis, with more fine chromatin. As far as looking like monocytes – I can see why you’d say that – they are fairly large, and somewhat oddly shaped (monocytes often have a horseshoe or irregular nucleus). However, if we could see the real case, and compare these cells with monocytes, I think you’d be able to tell that the chromatin pattern is different. Monocytes have a “raked” chromatin pattern (looks like someone dragged one of those Zen garden little rakes across the nucleus). Also, they don’t have clefted nuclei, like these cells do. These clefts are really deep and distinctive. Monocyte nuclei often have a little indentation on one side of the nucleus, but it doesn’t fold up into a cleft like these cells do. Good comment!
Some say that reactive lymphocytes look like a skirt of cytoplasm is surrounding the nucleus. Do you accept that?
Yes – there is a particular kind of reactive lymphocyte called a Downey 3 cell that has a ton of cytoplasm that flows around the cell and has little radial condensations that look like skirt pleats. 🙂
i thought they looked like cleaved lymphos…only the cytoplasm was a bit more than i ‘d expect in a cleaved lymphocyte…this could be the picture in a Tcell lymphoma too ??
is it a dx point…that reactive lymphos reach out to touch the RBCs…
i saw 2 posts to this effect:
“…the way they â€surround†erythrocytes is typical of reactive lymphocytes….”
“…and it reaches out to touch the red cells around it. …”
Yes – T cell leukemias/lymphomas often have larger cells with irregularly-shaped nuclei. Reactive lymphocytes often have a lot of cytoplasm which is so voluminous that it touches the surrounding red cells. It’s not a diagnostic requirement, by any means – there are a lot of different types of reactive lymphocytes, and many do not have voluminous cytoplasm.
Tanx Kristine !
Microphotographs are excellent, very sharp and real color, the description text is very precise and understandable, my compliment. What you used to catch the pics on the microscope: Photo ocular or cam for microscope, and what was the resolution?