Johanson-Blizzard syndrome

What causes Johanson-Blizzard syndrome?

Johanson-Blizzard syndrome is caused by mutations (changes) to the UBR1 gene. This gene provides instructions to the body to produce a protein that is important for the function of the pancreas. This protein is produced in specific cells in the pancreas called acinar cells. Acinar cells are important because they help produce digestive enzymes which allow the pancreas to break down food and use the food products for growth (malabsorption). Because people with Johanson-Blizzard syndrome have a UBR1 gene that is not functioning correctly, the acinar cells of the pancreas are destroyed and the pancreas cannot break down fats and other nutrients as well. This leads to many of the symptoms of JBS such as slow growth.

Johanson-Blizzard syndrome is inherited in an autosomal recessive manner. This means that both copies of the UBR1 gene (one inherited from the mother and one inherited from the father) are not working in people who have JBS. Any future children with the same mother and father will have a 25% chance of having JBS.

Last updated on 05-01-20

How is Johanson-Blizzard syndrome inherited?

Johanson-Blizzard syndrome is inherited in an autosomal recessive manner. This means that both copies of the __UBR1 gene (one inherited from the mother and one inherited from the father) have a mutation and are not working.

Affected people inherit one mutation from each of their parents. The parents, who each have one mutation, are known as carriers. Carriers of an autosomal recessive condition typically do not have any signs or symptoms (they are unaffected). When 2 carriers of an autosomal recessive condition have children, each child has a:

  • 25% chance to be affected
  • 50% chance to be an unaffected carrier like each parent
  • 25% chance to be unaffected and not a carrier

For someone who has Johanson-Blizzard, they have a mutation in both copies of their UBR1 gene. When that individual goes to have children, they will automatically pass on one mutation to their child, making their child a carrier. The only way for the child to be affected is if their other parent is a carrier for Johanson-Blizzard syndrome and also passes on a copy of the gene with a mutation, resulting in the child inheriting two mutations in the UBR1 gene.

Last updated on 05-01-20

What is the long-term outlook for people with Johanson-Blizzard syndrome?

The severity of the symptoms in Johanson-Blizzard syndrome (JBS) varies. While some patients may develop life-threatening complications during infancy, other have a less severe disease. Although intellectual disability does occur, in some cases, intelligence is normal. Hearing loss or deafness may be present at birth or may develop later during life. Growth deficiency associated with JBS may occur because of malabsorption and exocrine pancreatic insufficiency. Without treatment, impairment of the pancreas and malabsorption can progress to cause life-threatening complications like infections and malnutrition. Specific treatment of the pancreatic insufficiency and hypothyroidism can result in a better outlook.

Life expectancy depends more in the pancreatic insufficiency and the malnutrition that may lead to death in infancy or early childhood, but for patients managed early with efficient pancreatic enzyme and vitamin supplementation, survival into adulthood is not rare.

Last updated on 05-01-20

How might Johanson-Blizzard syndrome be treated?

The treatment of Johanson-Blizzard syndrome focuses on the specific symptoms that are present in each individual. Those with pancreatic insufficiency may require pancreatic enzyme supplements (e.g., oral pancreatin) to promote proper absorption of fats and other necessary nutrients. Vitamin supplements may also be needed to prevent or treat vitamin deficiencies that may result from malabsorption due to pancreatic insufficiency. A special diet with easily-absorbed, high-protein supplements may also be prescribed to ensure that total nutritional requirements are met. Although these therapies usually lead to improved nutrient absorption and weight gain, most affected children still remain smaller and shorter than average for their ages. A surgery for pancreas removal (pancreatectomy) and with islet autotransplantation (TPIAT) should be used only as a last resort for patients with severe symptoms of pancreatitis.

Individuals with hypothyroidism may need thyroxine hormone replacement therapy. Other abnormalities such as craniofacial, genitourinary, cardiac, and/or other malformations associated with the condition may be treated with surgery. Dental abnormalities may be treated with bonding agents, use of dentures, and/or other techniques. Hearing loss may be treated with hearing aids. Early intervention is important to ensure that children with JBS reach their full potential. Affected children may benefit from special remedial education, special social support, and other medical, social, and/or vocational services.

Last updated on 05-01-20

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The RareGuru disease database is regularly updated using data generously provided by GARD, the United States Genetic and Rare Disease Information Center.

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