Farber disease

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Other Names: Farber lipogranulomatosis; Ceramidase deficiency; Acid ceramidase deficiency; AC deficiency; N-Laurylsphingosine deacylase deficiency; Farber's disease Farber disease is an inherited lipid storage disease in which an excess amount of fat builds up in the joints, tissues, and central nervous system.

Types

Researchers have described seven types of Farber lipogranulomatosis based on their characteristic features. Type 1 is the most common, or classical, form of this condition and is associated with the classic signs of voice, skin, and joint problems that begin a few months after birth. Developmental delay and lung disease also commonly occur. Infants born with type 1 Farber lipogranulomatosis usually survive only into early childhood. Types 2 and 3 generally have less severe signs and symptoms than the other types. Affected individuals have the three classic signs and usually do not have developmental delay. Children with these types of Farber lipogranulomatosis typically live into mid- to late childhood. Types 4 and 5 are associated with severe neurological problems. Type 4 usually causes life-threatening health problems beginning in infancy due to massive lipid deposits in the liver, spleen, lungs, and immune system tissues. Children with this type typically do not survive past their first year of life. Type 5 is characterized by progressive decline in brain and spinal cord (central nervous system) function, which causes paralysis of the arms and legs (quadriplegia), seizures, loss of speech, involuntary muscle jerks (myoclonus), and developmental delay. Children with type 5 Farber lipogranulomatosis survive into early childhood. Types 6 and 7 are very rare, and affected individuals have other associated disorders in addition to Farber lipogranulomatosis.

Epidemiology

Farber lipogranulomatosis is a rare disorder. About 80 cases have been reported worldwide.

Cause

Mutations in the ASAH1 gene cause Farber lipogranulomatosis. The ASAH1 gene provides instructions for making an enzyme called acid ceramidase. This enzyme is found in cell compartments called lysosomes, which digest and recycle materials. Acid ceramidase breaks down fats called ceramides into a fat called sphingosine and a fatty acid. These two breakdown products are recycled to create new ceramides for the body to use. Ceramides have several roles within cells. For example, they are a component of a fatty substance called myelin that insulates and protects nerve cells. Mutations in the ASAH1 gene lead to severe reduction in acid ceramidase, typically to below 10 percent of normal. As a result, the enzyme cannot break down ceramides properly and they build up in the lysosomes of various cells, including in the lung, liver, colon, muscles used for movement (skeletal muscles), cartilage, and bone. The buildup of ceramides along with the reduction of its fatty breakdown products in cells likely causes the signs and symptoms of Farber lipogranulomatosis. It is unclear whether the level of acid ceramidase activity is related to the severity of the disorder.

Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Signs and symptoms

The following list includes the most common signs and symptoms in people with Farber disease. These features may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list does not include every symptom or feature that has been described in this condition Signs and symptoms of Farber disease may include:

• Joint pain and swelling (arthralgia)
• Failure to thrive
• Enlarged liver (hepatomegaly)
• Hoarse cry due to a soft, floppy voice box (laryngomalacia)
• Lumps of fat under the skin and around the joints (periarticular subcutaneous nodules)
• Short stature
• Developmental delay
• Symptoms typically appear in the first few weeks of life. In severe cases, both the liver and spleen are enlarged. Seven types of Farber disease have been described, each with slightly different characteristics. Types 4 and 5 are generally associated with severe neurological problems.

Diagnosis

Farber disease is diagnosed through a clinical history and exam and specialized tests looking for abnormalities in white blood cells. Genetic testing may also be used to confirm the diagnosis.

Treatment

Treatment for Farber disease is focused on managing the symptoms. Corticosteroids can be given to help with pain. Individuals with difficulty breathing due to swelling and abnormal fat build-up in the upper airway may require a breathing tube (tracheostomy). In some cases, surgery or a bone marrow transplant may be helpful. Specialists involved in the care of someone with Farber disease may include:

• Medical geneticist
• Neurologist
• Rheumatologist
• Pain management specialist
• Otolaryngologist (ENT)

NIH genetic and rare disease info

• NIH info on Farber disease

Farber disease is a rare disease.

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