JANSEN DISEASE

JANSEN DISEASE

Jansen disease, also known as Jansen type metaphyseal chondrodysplasia, is an extremely rare progressive disorder. Affected individuals show unusually short arms and legs and short stature (short-limbed dwarfism). It occurs because of the portion of the bones of the arms and legs that develop abnormally with unusual cartilage formation and subsequent abnormal bone formation at the large (bulbous) end portions (metaphyses) of these long bones (metaphyseal chondrodysplasia).

Infants with Jansen disease may have some changes and abnormalities in his or her facial features and additional skeletal malformations. Abnormal cartilage and bone development may also affect other bones of the body, particularly those of the hands and feet (i.e., metacarpals and metatarsals).

Affected individuals may begin to show progressive stiffening and swelling of many joints and/or an unusual “waddling gait” and squatting stance, in their childhood. As they grow up, affected adults may eventually develop abnormally hardened (sclerotic) bones especially in the back of the head (cranial bones).In some cases, these may lead or cause blindness and/or deafness. These people have abnormally high levels of calcium in the blood (hypercalcemia)

The variety and severity of symptoms may depend from person to another person. The common cases of Jansen disease are genetic changes.

SYMPTOMS

In Jansen disease, portions of the bones of the arms and legs develop abnormally with unusual cartilage formation and subsequent abnormal bone formation at the large (bulbous) end portions (metaphyses) of these long bones (metaphyseal chondrodysplasia). As a result, affected individuals exhibit unusually short arms and legs and short stature (short-limbed dwarfism)

Findings often become apparent during childhood. As affected individuals age, abnormal cartilage formation in affected areas may harden into rounded (bulbous) masses of bone, which may become prominent. Abnormal cartilage development and bone formation may also affect other bones of the body, including those of the hands and feet (i.e., metacarpals and metatarsals). This is an extremely rare progressive disorder.

Most infants have characteristics and facial abnormalities (congenital) that are caused by Jansen disease. These include an unusually small jaw (micrognathia), receding chin, highly-arched roof of the mouth (palate), unusually wide fibrous joints between bones of the skull (cranial sutures), and/or prominent, widely spaced eyes.

In childhood, affected individuals don’t have a normal count of bones. They have additional skeletal abnormalities such as typically short, clubbed fingers, with permanent fixation of the fifth finger in a bent position, an abnormally small lower rib cage, fractured ribs and/or malformations of the spine and pelvis. As affected children grow up, they may eventually develop abnormal front-to-back and side-to-side curvature of the spine and bowing of the legs. Also, short stature becomes more revealing as affected children age; the torso grows longer, but the arms and legs do not grow proportionally.

Affected children may also suffer diminished muscle mass and gradual swelling of particular joints, hips, and knees. These may become stiff and painful at certain movements, especially bending. Affected children develop an unusual semi-squatting stance and a “waddling” walk. Eventually, certain joints may become fixed in a permanently bent position.

DIAGNOSIS

The diagnosis may be confirmed by a thorough clinical evaluation, identification of characteristic physical findings, and a variety of specialized tests, particularly advanced imaging techniques. These techniques may show abnormal development of the large ends of certain bones of the body, particularly those of the arms and legs. Laboratory tests that detect abnormally high levels of calcium in the urine and blood are helpful in confirming the diagnosis.

TREATMENT

Jansen disease treatment is directed toward the specific symptoms that are apparent in each individual. Treatment may require the coordinated efforts of a team of specialists.

Correcting certain specific findings associated with this disease is done with the help of physical therapy or orthopedic surgery, such as deformities of the joints.

Early involvement is important to make sure that children with Jansen disease reach their highest potential. Special services like speech therapy, special therapy, special social support, physical therapy, and other media, social and/or vocational services can be beneficial to affected children.

Other treatments for this disorder is symptomatic and supportive. Genetic counseling is recommended for affected individuals and their families.

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