Clinical Characteristics of Japanese Patients with Palmoplantar Pustulosis. 
Palmoplantar pustulosis (PPP) is a chronic inflammatory disorder characterized by sterile pustules predominantly involving the palms and soles.  The purpose of this review was to describe the characteristics of Japanese PPP patients as PPP is frequently observed within the Japanese population.  Most Japanese dermatologists consider PPP a distinct entity, and co-existence of PPP and psoriasis is rare; however, outside Japan, PPP is often considered to be palmoplantar psoriasis, and an extra-palmoplantar lesion associated with PPP is considered to be psoriasis.  PPP frequently develops or exacerbates following focal infections such as tonsillitis, odontogenic infection, and sinusitis, either with or without arthralgia.  Pustulotic arthro-osteitis (PAO) is a major comorbidity of PPP, most often affecting the anterior chest wall.  In Japanese patients, PAO is frequently seen, whereas cases of SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome with symptoms other than PPP and sternocostoclavicular joint pain are extremely rare.  A difference in incidence depending on race suggests that different genetic backgrounds may be responsible for susceptibility to these disorders.  The treatment of focal infections often results in dramatic effects on cutaneous lesions, as well as joint pain.  The characteristics of Japanese patients with PPP are female predominance, mostly smokers, rare co-existence with psoriasis, frequent association with PAO, almost no accompanying celiac disease, and closely associated with focal infection.  PPP should be separately considered from palmoplantar psoriasis.