Lethal-type popliteal pterygium syndrome (LPPS), described as an autosomal-recessive form of popliteal pterygium syndrome (PPS) and also known as Bartsocas-Papas syndrome (BPS), is characterized by a more severe phenotype than that associated with the autosomal-dominant form. LPPS is characterised by multiple popliteal pterygia, cutaneous syndactyly, lack of nails, ankyloblepharon, filiform bands between the jaws, hypoplastic external genitalia, cleft lip and/or palate, and fetal or neonatal lethality, although, in the latter case, survival into childhood and beyond has been reported. It has been shown that recessive mutations in RIPK4 cause LPPS.
