Adams-Oliver syndrome (AOS; OMIM 100300) typically comprises a combination of congenital scalp defects and terminal transverse limb defects. Recently, mutations in ARHGAP31 and RBPJ have been found causing autosomal dominant forms of AOS. We describe a four-generation pedigree with isolated terminal limb defects and a truncating mutation in ARHGAP31. This finding underscores the relevance of sequencing ARHGAP31 in similar cases of isolated limb defects, irrespective of the presence of a complete AOS phenotype. We also highlight the variability of clinical features among mutation carriers, ranging from severe reduction defects to mild as well as clinically unaffected cases suggesting reduced penetrance.