To the Editor. —
Sansores et al1 reported that 51% of Mexican patients with pigeon breeder's disease (PBD) had finger clubbing and that this was associated with an adverse prognosis. This observation is of considerable clinical importance, but it is contrary to previous reports2 that have suggested that clubbing is a rare phenomenon in hypersensitivity pneumonitis. Our clinical experience3 in the United Kingdom suggests that clubbing is unusual in PBD. Hypersensitivity pneumonitis is, however, a complex and diverse clinical syndrome, and differences between populations may provide clues to factors that determine the manifestations of the disease.In the United Kingdom, pigeons are kept mainly for the sport of racing, and this is usually a hobby of men in contrast with the preponderance of women in the Mexican series. The average number of pigeons kept is about 80 and antigen exposure tends to be intermittent and of high intensity.