Autosomal recessive primary hypertrophic osteoarthropathy-2 (PHOAR2) is a rare disorder characterized by digital clubbing, pachydermia, and periostosis. Pain and swelling of ankles and knees, watery diarrhea, and excessive sweating are often present. Males are more frequently and severely affected (summary by Zhang et al., 2013, Li et al., 2017). For a discussion of genetic heterogeneity of PHO, see PHOAR1 (259100).