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Monthy Case Studies - 1999
Case #4 - January, 1999
A boy with diarrhea was seen by a physician in Baltimore, MD. The stained specimen (modified acid-fast method) was sent to CDC by the Maryland State Department of Health and Mental Hygiene for confirmation. The diameter of the objects is approximately 3.3 micrometers. What is your diagnosis? Based on what criteria?
Figure A
Answer to Case #4
Figure A below shows round, acid-fast objects that resemble Cryptosporidium (arrows). However, the diagnosis cannot be confirmed because:
- the size of the objects (about 3.3 micrometers) was smaller than the normal range of Cryptosporidium (four to six micrometers).
- there was substantial size variation.
- they lacked a visible oocyst wall.
In comparison, Figure B shows typical oocysts of Cryptosporidium. Diagnostic features include:
- a diameter of 4.4 micrometers
- a uniform size
- visible oocyst walls (green arrow)
- visible sporozoites (red arrow). Sporozoites can often be seen in oocysts of Cryptosporidium, but not in those of Cyclospora.
A direct fluorescent antibody (FA) assay performed at CDC was negative, confirming that the objects in this case were artifacts.
Figure A
Figure B
More on: Artifacts
Images presented in the monthly case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.
