The symptoms and physical findings associated with diastrophic dysplasia may be extremely variable, differing in range and severity even among affected family members (kindreds). However, in all individuals with the disorder, there is abnormal development of bones and joints of the body (skeletal and joint dysplasia).
During normal development before birth (embryonic and fetal development) as well as development during early childhood, cartilage in many areas of the body is gradually replaced by bone (ossification). In addition, a layer of cartilage (epiphyseal cartilage [growth plate]) separates the shafts (diaphyses) of long bones (e.g., bones of the arms and legs) from their ends (epiphyses), allowing long bones to grow until the cartilage is no longer present. In those affected by diastrophic dysplasia, however, there is delayed growth before and after birth (prenatal and postnatal growth retardation), the development of the ends of the long bones (epiphyses) is irregular, and the ossification of the epiphyses is delayed. Thus, affected newborns and children typically have markedly short, bowed arms and legs and Short stature (short-limbed dwarfism). In addition, in such cases, growth failure is typically progressive, in part due to absence of the “growth spurt” that usually occurs during puberty. The severity of such growth failure may vary greatly from case to case, including among affected siblings.
Due to abnormalities of skeletal development, infants and children with diastrophic dysplasia also have additional distinctive malformations of bones of the hands, feet, and other areas of the body. For example, the first bone within the body of each hand (first metacarpals) may be unusually small, short, and “oval shaped.” As a result, the thumbs deviate away (abduction) from the body (“hitchhiker thumbs”). In addition, other fingers may be abnormally short (brachydactyly) and joints between particular bones of the fingers (proximal interphalangeal joints) may become fused (symphalangism), causing limited flexion and restricted movement (reduced mobility) of the finger joints. In some cases, bones of the wrists may also be malformed due to premature ossification.
Infants with the disorder also typically have severe foot deformities (talipes or “clubfeet”) due to abnormal fusion and deviation of bones within the body of each foot (metatarsals). In most cases, the heels turn outward (talipes valgus) while the fore part of each foot deviates inward (metatarsus adductus). In other infants, the soles of the feet may be flexed (talipes equinus) and, in some cases, the heels may also turn inward (talipes equinovarus). The great toes, like the thumbs, may also deviate away (abduction) from the body.
In addition to having limited flexion of finger joints, many affected infants and children also experience partial dislocation (subluxation) and/or complete dislocation of particular joints of the body. For example, in many cases, dislocations of the knees and hips occur upon weightbearing. Affected individuals may also have abnormally loose and/or stiff joints; experience limited extension of joints at the elbows and/or knees; and/or develop permanent flexion and immobilization (contracture) of certain joints (e.g., knees). Due to joint and bone abnormalities such as those affecting the feet, many individuals with diastrophic dysplasia have a tendency to walk on tiptoe. In addition, affected individuals may be predisposed to degenerative changes (osteoarthrosis) of particular joints (e.g. of the hips), resulting in pain with use of the joint, tenderness, stiffness, and, in some cases, deformity.
Many infants with diastrophic dysplasia also have abnormalities of bones within the spinal column (vertebrae). For example, in most affected infants, there may be incomplete closure of vertebrae (spina bifida occulta) within the neck area and the upper portion of the back (lower cervical and upper thoracic vertebrae) and/or abnormal narrowing of portions of the vertebrae of the lower back (interpedicular narrowing in lumbar vertebrae). During the first year of life, some infants may begin to develop progressive abnormal sideways curvature of the spine (scoliosis). In addition, during adolescence, individuals with diastrophic dysplasia may also develop abnormal front-to-back curvature of the spine (kyphosis), particularly affecting vertebrae of the neck region (cervical vertebrae). In severe cases, progressive kyphosis may result in Difficulties Breathing (respiratory distress). Some individuals with the disorder may also be prone to experiencing partial dislocation of joints between the central areas (bodies) of cervical vertebrae (cervical subluxation), potentially resulting in compression of the spinal cord. (This cylindrical structure of nerve tissue extends from the lower portion of the brain and is located inside the central canal within the spinal column [spinal cavity].) Such spinal cord injury may result in Muscle Weakness (paresis) or Paralysis and/or life-threatening complications.
Most newborns with diastrophic dysplasia also have or develop fluid-filled sacs (cysts) within the outer, visible portions of the ears (pinnae). Within approximately two to five weeks after birth, the pinnae become swollen and inflamed. When such swelling and inflammation subside, the pinnae remain unusually thick, hard, and abnormal in shape. The abnormal areas of tissue (lesions) may gradually accumulate deposits of calcium salts (calcification) and eventually be replaced by bone (ossification). Although affected infants may experience associated abnormal narrowing (stenosis) of the external ear canal (external auditory canal), hearing is usually normal. However, according to reports in the literature, other affected infants and children may experience hearing impairment due to such auditory canal stenosis or abnormal fusion or absence of the three tiny bones (auditory ossicles) in the middle ear that conduct sound to the inner ear.
Some infants with diastrophic dysplasia also have characteristic malformations of the head and facial (craniofacial) area, such as an unusually high, prominent forehead; abnormal smallness of the jaws (micrognathia); and/or a broad, highly arched roof of the mouth (palate) or incomplete closure of the palate (cleft palate). Cleft palate has been reported to occur in anywhere from 25 to 60% of affected infants, and may cause Difficulties with feeding and/or breathing. In addition, in some infants with diastrophic dysplasia, abnormalities of supportive connective tissue (cartilage) within the windpipe (trachea), voice box (larynx), and air passages in the lungs (bronchi) may cause abnormal narrowing (e.g., laryngotracheal stenosis) and collapse of such airways. In such cases, life-threatening complications such as respiratory obstruction and Difficulties Breathing (respiratory distress) may result. However, in many cases nasal speech (hyponasality) occurs as a result of the abnormally shaped vocal tract.
Approximately one third of infants and children with diastrophic dysplasia also have dental abnormalities, such as abnormally small teeth and dental crowding. In addition, in some cases, affected infants may have benign, reddish purple growths in the midportion of the face (midline frontal hemangioma) due to an abnormal distribution of tiny blood vessels (capillaries). Some individuals with the disorder may also have additional symptoms and physical findings.