Diagnostic dilemma: An 83-year-old man went to the hospital because of very itchy skin. It turned out he had a rare form of syphilis.

The patient: An 83-year-old man in Belgium

The symptoms: The man sought medical attention at a hospital because the muscles on one side of his face had weakened suddenly, causing it to droop — a condition called unilateral peripheral facial-nerve palsy. He had also recently had a fever, which had since resolved.

Tests run by the neurology department found the man had anemia, fatty liver disease and an enlarged spleen. Combined with his recent fever, these findings led the team to assume he had a viral infection. However, he tested negative for a variety of germs, including Epstein-Barr virus, which causes mono; cytomegalovirus; human immunodeficiency virus (HIV); and hepatitis A, B, C, and E.