(a,c,e) Full presentation of ichthyosis vulgaris in FLG−/− individuals. (b,d,f) A milder but still readily recognizable phenotype in a FLG R501X heterozygote. Pedigrees are shown in Figure 2. (a) Diffuse, fine superficial scaling is seen here on the lower abdomen of this individual lacking filaggrin (R501X/2282del4 compound heterozygote, family 6, I:2). Scaling was widespread and obvious in this patient and other homozygous or compound heterozygous patients. (b) Fine scaling seen here in a close-up view of the calf of an R501X heterozygote (family 1, II:2). Scaling was less obvious and tended to have a less widespread distribution overall in heterozygotes. (c) Marked palmar hyperlinearity seen in an R501X homozygous patient (family 1, III:2). This phenotype becomes more marked with age. The patient shown here is 14 years of age, but note that the hands appear prematurely aged compared with his heterozygous father (d). (d) Palmar hyperlinearity is less marked in this R501X heterozygote (family 1, II:2) but is still readily discernable, particularly on the palmar surface of the proximal phalanges. (e) Enlargement of c showing the marked palmar hyperlinearity on the thenar eminence of this R501X homozygote, compared with his heterozygous father (f). (f) Enlargement of d showing the less pronounced palmar linearity on the thenar eminence of this R501X heterozygote.