What is Small patella syndrome?

Small patella syndrome is a rare genetic limb malformation syndrome which is characterized by absence or underdevelopment of the patella, ischiopubic junction abnormal ossification. Other findings include hallux varus, brachymetatarsia affecting the fourth and fifth metatarsals, flat feet, and the presence of an enlongated edial patellofemoral ligament. Less common findings include micrognathia, cleft palate, frontal bossing and nose prominence. Complications include infancy-onset recurrence of luxations, pain of the knee, impaired ability of running and riding bicycles, and late-onset gonarthrosis, although it is not uncommon for some cases to be asymptomatic. This condition is caused by autosomal dominant mutations in the TBX4 gene, in chromosome 17. Around 50-70 cases have been described in medical literature. Diagnosis is made through genetic testing and radiography.