In addition three are two other opportunistic pathogens that are dimorphic. Sporothrix schenckii causes "rose picker's disease," and must be traumatically implanted under the skin to cause infection. The other is Penicillium marneffei, which is an opportunistic fungal pathogen so far found only in southeast Asia.
The remaining 5% develop a chronic progressive lung disease, a chronic cutaneous or systemic disease, or an acute fulminating rapidly fatal systemic infection. The latter form is particularly common in children. Following infection there is an acute alveolitis, and macrophages engulf the organism, resulting in an inflammatory reaction. Macrophages probably carry the organism to other parts of the body very early in the course of the infection.
There is a skin test for histoplasmosis that was developed in 1941 by Van Perris. The fungus grown in broth and filtered. The filtrate is inoculated under skin-a red area at least 5 mm after 48 hours is considered a positive test.
According to skin tests, the largest area with high prevalence is the middle section of the North American continent-- E.g in a series of tests in Kansas City, by age 20, 80-90% of population had a positive histoplasmin skin test. There have been similar results in other areas. So the histoplasmin skin test merely indicates that one has lived in the central USA for a time, and has no diagnostic value.
In 1997 it was reported in the press that Bob Dylan (yes that Bob Dylan) was suffering from Histoplasmosis, but his was a very unusual form, infecting the lining of his heart. This usually signifies some underlying health problems, but since I am not a medical doctor I will not speculate. So where did Bob Dylan pick up histoplasmosis? This is an Audio Daily Double. Click here and pick your choice for an answer.
However, please do not write to me about any of your medical problems caused by fungi. I am not a medical doctor. Someday I'll write about the mysterious unsolicited package I received in the mail from someone who read my web page in southern California. I'm still really fuming about that one.
Here are some very good links to learn more about Histoplasmosis
Many thanks to Dr. John Rippon, Dr. Al Rogers, and Dr. Tex Beneke for providing this month's pictures. I believe they're all in Paris as I write this, celebrating the year 2000. Happy New Year to them and to you.
Return to Tom Volk's Fungus of the month pages listing