Week 21 Q&A
A newborn male is found to have hyperextended knees and bilateral clubfeet.
Both hips are flexed and have limited abduction; the spine appears straight and without any cutaneous lesions. The pregnancy was unremarkable, other than decreased fetal movement on prenatal ultrasounds.
All of the following would be consistent with a diagnosis of amyoplasia EXCEPT:
A. Cognitive delay.
B. Lack of flexion creases at joints.
C. Bilateral hip dislocations.
D. Difficulty swallowing.
The correct answer is “A.” Arthrogryposis is the presence of congenital joint contractures, usually associated with decreased fetal movement due to either a restricted intrauterine environment or intrinsic muscular or neurologic disorders, and occurs in approximately 1 in 10,000 live births. The most common cause is amyoplasia, an abnormality of muscle development often referred to as arthrogryposis multiplex congenita. Arthrogryposis may also occur in patients with abnormalities of the central nervous system, in the presence of oligohydramnios, or in certain genetic syndromes, such as diastrophic dysplasia or Larsen syndrome. In addition to the multiple joint contractures, which can include hand and foot deformities as well as dislocate hips, amyoplasia is characterized by cylindrical-shaped limbs with lack of flexion creases, dimpling at joints, and normal cognitive function. Difficulty swallowing and breathing may occur at birth. Abnormal cognitive development would suggest an underlying neurologic abnormality as the cause of multiple joint contractures.