MAFB-related conditions are inherited in an autosomal dominant manner. A positive result means that a pathogenic (disease-causing) or likely pathogenic variant was found in the MAFB gene. MAFB-related conditions include Multicentric Carpotarsal Osteolysis Syndrome (MCOS) with or without nephropathy and Duane retraction syndrome 3. Features of MAFB-related conditions may vary from person to person. MCOS with or without nephropathy is a condition that affects the bones and joints, and in some patients, the kidney. Signs and symptoms usually begin in early childhood with swelling and pain in the joints that is similar to juvenile rheumatoid arthritis. Progressive bone disease of the carpal and tarsal bones in the hands/wrist and feet is typical, and other bones may also be involved. Intellectual disability and minor facial abnormalities have been noted in some patients. Kidney disease in MCOS oftens begins with protein in the urine (proteinuria) in infancy or childhood. Over time the kidney disease progresses and can result in End Stage Renal Disease (ESRD).
Some individuals with MCOS also have high blood pressure (hypertension), which can cause further damage to the blood vessels in the kidneys.
Duane retraction syndrome 3 is characterized by abnormal eye movement, which is usually present at birth. Affected individuals have strabismus (improper eye alignment) due to limited ability to move the eyes horizontally. If this condition is undiagnosed in children, it can lead to permanent loss of vision. Some individuals with this condition will also have sensorineural hearing loss (hearing loss related to inner ear abnormality). Individuals with Duane retraction syndrome 3 are not expected to have kidney disease.
It is sometimes but not always possible to determine if a variant in the MAFB gene will cause MCOS with or without nephropathy or Duane retraction syndrome 3.