Infantile-onset X-linked spinal muscular atrophy

Definition

A rare form of spinal muscular atrophy characterized by the neonatal onset of severe hypotonia, areflexia, profound weakness, multiple congenital contractures, facial dysmorphic features (myopathic face with open, tent-shaped mouth), cryptorchidism, and mild skeletal abnormalities (i.e. kyphosis, scoliosis), that is often preceded by polyhydramnios and reduced fetal movements in utero and followed by bone fractures shortly after birth. Muscle weakness is progressive and chest muscle involvement eventually leads to ventilatory insufficiency and respiratory failure.