Jansen Type Metaphyseal Chondrodysplasia
What is Jansen type metaphyseal chondrodysplasia?
Jansen type metaphyseal chondrodysplasia is a progressive skeletal disorder that usually appears in early childhood, leading to altered development in the skeleton. Parts of the arm and leg bones develop abnormally, with abnormal cartilage formations that lead to unusual bone formations at the large end portions of these long bones. Jansen type metaphyseal chondrodysplasia is extremely rare, with about 20 cases having been reported in medical literature. It affects males and females equally.What are the symptoms of Jansen type metaphyseal chondrodysplasia?
Severity and range of symptoms can range from person to person. These symptoms can include:- Short stature
- Short limbs
- Abnormal cartilage and bone development in the hands and feet
- Waddling walk
- Deformed, swollen joints
- Prominent upper face, small jaw, receding chin, and widely spaced eyes
- Bowed legs
- Short, clubbed fingers that may be permanently bent
- Lowered muscle mass
- Chronic parathyroid hormone-independent hypercalcemia (unusually high levels of calcium in the blood)
- Hypercalciuria (unusually high levels of calcium in the urine)
- Mild hypophosphatemia (unusually low levels of phosphate in the blood)
- As individuals age, the cartilage formations can harden into bulbous masses of bone that may become prominent
- In adults, blindness and/or deafness
What causes Jansen type metaphyseal chondrodysplasia?
Most cases are a result of spontaneous mutations, meaning that they occur in people with no family history of the disorder. However, some cases of this disorder are inherited in an autosomal dominant pattern. Human traits are inherited from a person’s father and mother; each one contributes a copy of a gene, which interacts with the other copy. Since the disorder is inherited in a dominant pattern, only one copy of the mutation must be inherited for the individual to exhibit the disease. The disorder is caused by mutations of a gene that creates a specific protein called the PTH/PTHrP receptor. Parathyroid hormone helps regulate calcium levels in the blood, which is why patients with this disease exhibit unusual calcium levels with this disorder.How is Jansen type metaphyseal chondrodysplasia diagnosed?
Diagnosis is usually suspected during infancy. It is done using the following procedures:- X-rays
- Thorough physical examination
- Laboratory tests examining unusually high levels of calcium in the urine and blood
- Detailed family history
What are the treatments for Jansen type metaphyseal chondrodysplasia?
Treatment focuses on addressing specific symptoms that appear in each patient. This treatment includes, but is not limited to:- Physical therapy
- Speech therapy
- Orthopedic surgery
- Genetic counseling
