Abstract
The frequency of various anomalies was compared in probands with Fanconi anaemia and their affected sibs. As probands are usually ascertained because of a 'characteristic' array of physical anomalies, the frequencies of these specific anomalies may be overestimated in probands, whereas their affected sibs may provide a more accurate estimate. The frequencies of growth retardation, skin hyperpigmentation, radial ray deformities, radial ray reduction deformities, hypogenitalia, and supernumerary thumbs were significantly lower in the affected sibs of probands than in probands. Since 25% of the affected sibs had no dysmorphic features, absence of dysmorphism is not sufficient to rule out the diagnosis.