Amyoplasia involving only the upper limbs or only involving the lower limbs with review of the relevant differential diagnoses.

Of individuals with Amyoplasia, 16.8% (94/560) involve only the upper limbs (Upper Limb Amyoplasia-ULA) and 15.2% (85/560) involve only the lower limbs (Lower Limb Amyoplasia-LLA). The accompanying paper deals with other forms of Amyoplasia [Hall et al., 2013] and discusses etiology. An excess of one of monozygotic (MZ) twins is seen in both groups (ULA 4/94 (4.3%), LLA 5/85 (5.9%)), gastrointestinal (GI) abnormalities thought to be of vascular origin (bowel atresia and gastroschisis) (ULA 16/94 (17%), LLA 4/85 (4.7%)), small or partial absence of digits (ULA 6/94 (6.2%), LLA 8/85 (9.4%)), and umbilical cord wrapping around the limbs at birth (ULA 3/94 (3.2%), LLA 7/85 (8.2%)) (severe enough to leave a permanent groove). Pregnancy complications occurred in 42/60 (70%) of ULA and 36/54 (67%) of LLA. Prenatal diagnosis, after ultrasound usage became routine, occurred in only 7/25 (28%) of ULA and 5/12 (12%) of LLA. This series may represent an over estimate of the complications and associations occurring in ULA and LLA. Differential diagnoses separating LLA from the genetic forms of "lower limb only" arthrogryposis and ULA from "upper limb only" genetic forms of arthrogryposis and Erb's palsy is provided.