Reversal of digital clubbing after lung transplantation in cystic fibrosis patients: a clue to the pathogenesis of clubbing.

Digital clubbing is a common sign in cystic fibrosis (CF) and in a variety of other diseases. However, its pathogenesis remains obscure. In diseases other than CF, regression of clubbing has been noted after cure of the underlying disease. The aim of this study was to assess whether clubbing is reversible in CF patients after lung transplantation. Digital clubbing was investigated in 3 CF patients, prior to and after lung transplantation. Distal phalangeal depth (DPD) and interphalangeal depth (IPD) of the index finger were measured using a skinfold caliper, and the DPD/IDP ratio was calculated. The mean DPD/IDP ratio was 1.08 +/- 0.05 prior to transplantation and 1.00 +/- 0.06, 0.96 +/- 0.06, 0.92 +/- 0.04, and 0.89 +/- 0.07 at 3, 6, 12, and 24 months after transplantation, respectively. In all 3 patients, the DPD/IDP ratio was greater than 1 before transplantation. In 2 patients, this ratio decreased to less than 1 within 3 months, and in the third patient within 9 months after surgery. We conclude that digital clubbing is reversible in CF patients who undergo lung transplantation. Regression was usually noted during the first 3 months posttransplantation. This could be explained either by adequate inactivation of a circulating clubbing-inducing molecule by the normal transplanted lungs, or by removal of the diseased lungs in which this presumably causative substance was produced.