Histoplasmosis; a report of four cases, two in siblings; histoplasmin test and other diagnostic procedures.

Summary Four cases of histoplasmosis (two new and two previously reported) occurredin children living in a rural area in Loudoun County, Va., within a radius of ten miles of one another. The two new patients were brothers, constituting the first reported instance of histoplasmosis in siblings. Histoplasma capsulatum was isolated in culture premortem from both, although neither reacted to histoplasmin. The possibility of transmission from one brother to the other is considered. A search for an animal reservoir in this area was not successful. Histoplasmin reactions in guinea pigs with experimental moniliasis are reported. The skin reactions induced in other mycoses indicate that histoplasmin is not a suitable diagnostic agent.