MedGen

PHOAR2-enteropathy syndrome (PHOAR2E) is characterized by primary hypertrophic osteoarthropathy (PHO) and/or chronic nonspecific ulcers (CNSU) of the small intestine. The cardinal features of PHO are digital clubbing, pachydermia, and periostosis; other manifestations include swelling and pain of the large joints, hyperhidrosis, seborrhea, and acne. CNSU often presents with chronic unexplained anemia and abdominal pain, and patients may exhibit edema due to hypoalbuminemia. Radiologic imaging or endoscopy shows multiple small ulcers, predominantly in the ileum, although the stomach, duodenum, and jejunum are often involved. PHO is more frequent and more severe in male patients, who often also report watery diarrhea, whereas CNSU is more often diagnosed in female patients, who may also show features of PHO such as digital clubbing or arthralgias and swelling of the joints. The same mutations in the SLCO2A1 gene have been reported in patients presenting with either diagnosis, and presumed sex-related modifiers of the manifestations of disease or other genotype/phenotype correlates have yet to be elucidated (Li et al., 2017; Umeno et al., 2018; Hong et al., 2022; Kimball et al., 2024). For a discussion of genetic heterogeneity of PHO, see PHOAR1 (259100). [from OMIM]

Autosomal dominant primary hypertrophic osteoarthropathy (PHOAD) is characterized by 3 major features: digital clubbing, periostosis, and pachydermia. Patients may also experience joint swelling and pain, and some have reported gastrointestinal symptoms, including watery diarrhea. Males are more commonly affected, and more severely affected, than females (Lee et al., 2016; Xu et al., 2021). Touraine et al. (1935) recognized pachydermoperiostosis (PDP) as a familial disorder with 3 presentations or forms: a complete form with periostosis and pachydermia, an incomplete form without pachydermia, and a forme fruste with pachydermia and minimal skeletal changes. Genetic Heterogeneity Autosomal recessive forms of PHO have been reported (see 259100), including PHOAR2E (614441), which is also caused by mutation in the SLCO2A1 gene. Patients with autosomal recessive PHO do not experience gastrointestinal symptoms. [from OMIM]