The disorders of peroxisome biogenesis and peroxisomal Î²-oxidation that affect bile acid synthesis will be covered in the review by Ferdinandusse et al.he neurological presentation often includes signs of upper motor neurone damage (spastic paraparesis). The most useful screening test for many of these disorders is analysis of urinary cholanoids (bile acids and bile alcohols); this is usually now achieved by electrospray ionisation tandem mass spectrometry.