Arthrogryposis Multiplex Cong... Health Article

Definition

Arthrogryposis multiplex congenita (AMC) is a term used to describe the presence of two or more (multiplex) joint contractures (arthrogryposis) present at birth (congenita). A joint contracture is a limitation of the normal range of motion of a joint.

Description

There are at least 21 recognized forms of AMC. Ten of these fall into a category called the distal arthrogryposes. Four of these are syndromes that include AMC as a set of symptoms. Each involves at least two joint contractures evident from birth. None of the AMC disorders are progressive, meaning the symptoms do not worsen with age.

Distal arthrogryposis (DAs) are all characterized by contractures of the fingers and toes. Each type can be distinguished by specific characteristics:

• Type 1a DA: club feet that point inward and down (talipes equinovarus).
• Type 2 DA: down slanting of the opening between the upper and lower eyelids (palpebral fissures), a small mouth with pursed lips and malformations of the nose that cause a whistling appearance upon breathing, a curvature of the spine (scoliosis), and some instances of mild developmental retardation. Type 2b DA, is characterized by those characteristics of type 2 DA accompanied by earlobes that are attached to the skin of the face and a permanent bending (flexion) of one or more fingers (camptodactyly).
• Type 3 DA: talipes equinovarus, camptodactyly, short stature, and vertebral abnormalities.
• Type 4 DA: short stature, an abnormally short neck, immobile facial expressions, camptodactyly, and the lack of the normal prominent creases (flexion creases) on the palms of the hands.
• Type 5 DA: contractures of the arms and legs, limited eye movement, deep set eyes, and abnormal coloring of the retina of the eye.
• Type 6 DA: camptodactyly, an abnormally small head (microcephaly), and hearing loss caused by an abnormality of the auditory nerve (sensorineural hearing loss).
• Type 7 DA: camptodactyly when an affected individual attempts to open the hand, short stature, abnormally short muscles in the legs, and an inability to open the mouth completely (trismus).
• Type 8 DA: contractures of the wrist and/or ankles, short stature, and scoliosis.
• Type 9 DA: lack of muscle tone and development, abnormally low shoulder-to-shoulder width to body height ratio (marfanoid habitus), severe outward curvature of the spine in the neck and upper back (kyphoscoliosis), and contractures of the hips and shoulders.

The most serious forms of DA are types 6 and 9.

Signs and symptoms

The four syndromes that include arthrogryposis as a set of symptoms are cerebrooculofacioskeletal syndrome, adducted thumb-clubfoot syndrome, Saethre-Chotzen syndrome, and arthropathy-camptodactylypericarditis syndrome. Cerebrooculofacioskeletal (COFS) syndrome is characterized by an abnormally small head (microcephaly), a lack of muscle tone (hypotonia), eye defects, abnormally large ears and nose, a receding chin (micrognathia), and kyphoscoliosis. Adducted thumb-clubfoot syndrome is characterized by clubfoot (equinovarus talipes), clasped (adducted) thumbs, abnormally long fingers and toes (arachnodactyly), a prominent forehead, and psychomotor delay. Saethre-Chotzen syndrome is characterized by flattened facial features, wide set eyes (hypertelorism), abnormalities of the skull (craniosynostosis), abnormalities of the eyes, partially fused fingers or toes (syndactyly), congenital heart defects, and contractures of the elbows and knees. Arthropathy-camptodactyly-pericarditis syndrome is characterized by contractures of the elbows, wrists, and fingers; an abnormally elevated generalized stiffness upon waking; arthritis of the hips, shoulders, elbows, and knees; and, inflammation of the membranous sac that protects the heart (pericarditis).

The other forms of AMC include three relatively common forms: X-linked arthrogryposis, neurogenic arthrogryposis, amyoplasia; and four extremely rare forms that may or may not represent distinct disorders: spondylospinal thoracic dysostosis, Jarcho-Levin syndrome, prenatal growth retardation with pelvic hypolasia and arthrogryposis in the lower limbs, and lethal congenital contracture syndrome.

X-linked arthrogryposis is generally mild and affects only the legs. Neurogenic arthrogryposis is also relatively mild and affects only the elbows and the knees. Amyoplasia is the mildest form of arthrogryposis; it is generally sporadic in appearance. Amyoplasia is characterized by contractures of the wrists, elbows, and knees; club feet, and an abnormal internal rotation of the shoulders.

Spondylospinal thoracic dysostosis is characterized by a short, curved spine; a short neck; malformations of the bones of the mouth; abnormal ribs; and congenital heart defects. Jarcho-Levin syndrome is characterized by many of the same characteristics of spondylospinal thoracic dysostosis. These two disorders differ only in the presence of a fusion of certain spinal vertebrae in spondylospinal thoracic dysostosis that has not been observed in Jarcho-Levin syndrome. Prenatal growth retardation with pelvic hypoplasia and arthrogryposis in the lower limbs has only been described in a pair of sisters and four males and one female, all of whom were siblings. It seems likely that this disorder is one of the distal arthrogryposes. Lethal congenital contracture syndrome almost inevitably leads to prenatal death prior to week 32 of gestation. It appears to be a unique variant of AMC.