Primary Hypertrophic Osteoarthropathy: An Update on Patient Features and Treatment.

Hypertrophic osteoarthropathy (HO) is a disorder characterized by changes to the skin and bones, and occurs either in a rare familial primary form [primary hypertrophic osteoarthropathy, (PHO)], also called pachydermoperiostosis (PDP), with a 9:1 male:female prevalence ratio, or more commonly secondary to an underlying pathology1. Key features include digital clubbing, periostosis with bone and joint enlargement, and skin changes, such as pachydermia, abnormal furrowing, seborrhea, and hyperhidrosis. Specific developmental abnormalities have been found in some patients with PHO, such as wide cranial sutures, Wormian bones, and patent ductus arteriosus2. In adults, when all major clinical features are present, PHO is relatively easy to diagnose. However, for the pediatrician, who often has to contend with an incomplete clinical presentation3, diagnosis may be a challenge. The discovery of mutations in 2 prostaglandin pathway genes HPGD and SLCO2A1 has clarified the autosomal recessive inheritance [Mendelian Inheritance in Man (MIM) #259100, MIM #614441] of this genetically heterogeneous condition4,5,6,7. Here we present 4 previously undescribed patients who exemplify the gene-dependent presentations of PHO and provide diagnostic and treatment advice. The subjects’ written consent was obtained in conformance to the Declaration of Helsinki. Key clinical features are listed in Table 1. Secondary causes of HO were excluded8, and DNA sequence analysis (Supplementary Data available online at jrheum.org) confirmed the clinical diagnoses of PHO/PDP.