What causes Whipple disease and how is the diagnosis made?
- Whipple disease is caused by a gram-positive actinomycete called Tropheryma whipplei.
- The diagnosis is made by demonstrating periodic acid–Schiff (PAS)-positive inclusions in macrophages of affected tissues, typically a small bowel or lymph node biopsy sample.
- These deposits contain the rod-shaped free Tropheryma whipplei bacilli seen on electron microscopy.
- The diagnosis can be confirmed by a polymerase chain reaction (PCR) of the DNA sequence of the 16S-ribosomal RNA gene sequence of T.
- whipplei in the PAS-positive tissue sample. PCR testing of cerebrospinal fluid has also been used to confirm central nervous system (CNS) Whipple disease.
- PCR testing of synovial fluid and blood can be performed but has limited sensitivity in patients with untreated Whipple disease.
