It was 1990. A dengue epidemic. A child admitted with a confident diagnosis. And skin lesions that didn’t add up. Dr. Alberto recalls the case where clinical exam overrode everything — and what would have happened if it hadn’t.
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Infectious Diseases in Focus →Rio de Janeiro in 1990 was in the grip of a serious dengue epidemic. In Niterói — the city across the bay where Dr. Alberto was completing his infectious disease residency — the afternoon shifts had a particular character: the moment you finished rounding on existing patients, a new wave of admissions would begin. The wards were full. The diagnosis on almost every referral was the same: dengue.
That is the context in which a child arrived — approximately seven or eight years old, referred by a colleague who had made a confident diagnosis of dengue fever. The referral was detailed and well-documented. The initial laboratory results were consistent with a viral infection. There was no obvious reason to question the diagnosis.
Except for the skin.
When Dr. Alberto examined the child, the skin lesions he found were not what dengue fever looks like. They were small, purplish, and irregular. Not the petechiae of dengue — those tiny red pinpoint spots that appear when small blood vessels burst. Not the maculopapular rash that dengue can produce — flat, blotchy, similar to measles. Something different.
Meningococcemia is caused by Neisseria meningitidis — meningococcus — a bacterium that can cause both meningitis (inflammation of the brain’s lining) and septicemia (bacterial infection of the bloodstream). The skin findings are one of its most distinctive clinical features: purpura caused by the bacteria triggering bleeding into the skin as they spread through the bloodstream. This child had no neurological signs — no stiff neck, no photophobia, no altered consciousness. Just the skin. But the skin was enough.
Dr. Alberto made the decision before the confirmatory results came back. He started intravenous penicillin immediately — the treatment for meningococcal disease — while ordering a second complete blood count and a blood culture.
This is a critical clinical principle: when the diagnosis is uncertain but one of the possibilities is rapidly fatal if untreated, you treat for the dangerous one while you wait for confirmation. Penicillin does not harm a dengue patient. But withholding penicillin from a meningococcemia patient for even a few hours can be the difference between recovery and septic shock.
When the second blood count came back, the pattern had shifted dramatically:
| Test | First result | Second result |
|---|---|---|
| White cell count | Leukopenia (low) — viral pattern | Leukocytosis (high) — bacterial pattern |
| Differential | Lymphocytosis — viral pattern | Marked left shift — bacterial pattern |
| Interpretation | Consistent with dengue / viral | Consistent with severe bacterial infection |
The blood culture confirmed it: Neisseria meningitidis — meningococcus — growing in the child’s blood.
The child responded well to intravenous penicillin over seven days. The bacteremia cleared. But meningococcemia left its mark on the skin. As the disease had progressed before treatment began, the purpuric lesions had developed into deep ulcers — areas of skin necrosis where the tissue had been destroyed by the bacteria and the inflammatory response.
Fortunately, the child recovered fully and was eventually discharged. It was, as Dr. Alberto describes it, a case of genuine professional satisfaction — not because the outcome was dramatic, but because the clinical decision was made correctly, at the right moment, with the right degree of confidence and action.
The referring doctor had made a reasonable diagnosis in a dengue epidemic. Dengue was everywhere. The lab results were initially consistent. But having made that diagnosis, the doctor “dropped anchor” — and did not move. This is what cognitive scientists and medical educators call anchoring bias: the tendency to rely too heavily on the first piece of information encountered when making a decision.
If the child had been treated for dengue — supportive care, fluids, no antibiotics — the meningococcemia would have continued to progress. Within hours, septic shock becomes a real risk: blood pressure crashes, perfusion fails, organs begin to shut down. The ICU becomes necessary. Death becomes possible. None of that happened because one doctor looked at the skin and was willing to say: this is not dengue.