Which of the following organs is not involved in Whipple's disease ?

This rare condition is characterised by infiltration of small intestinal mucosa by 'foamy' macrophages, which stain positive with periodic acid-Schiff (PAS) reagent. The disease is a multisystem one and almost any organ can be affected, sometimes long before gastrointestinal involvement becomes apparent . Pathophysiology Whipple's disease is caused by infection with the Gram-positive bacillus Tropheryma whipplei, which becomes resident within macrophages in the bowel mucosa. Villi are widened and flattened, containing densely packed macrophages in the lamina propria, which obstruct lymphatic drainage and cause fat malabsorption. Clinical features Middle-aged Caucasian men are most frequently affected and presentation depends on the pattern of organ involvement. Low-grade fever is common and most patients have joint symptoms to some degree, often as the first manifestation. Occasionally, neurological manifestations may predominate and CNS involvement is the most serious consequence. Investigations Diagnosis is made by the characteristic features on small bowel biopsy, with characterisation of the bacillus by polymerase chain reaction (PCR). Management Whipple's disease is often fatal if untreated but responds well, at least initially, to intravenous ceftriaxone (2 g daily for 2 weeks), followed by oral co-trimoxazole for at least 1 year. Ref Davidson edition23rd pg 809