Deborah Marsden, MD, Global Medical Expert, Medical Affairs, Ultragenyx, gives an overview of mucopolysaccharidosis type VII (MPS VII).
MPS VII is a rare progressive metabolic condition that affects most tissues and organs. The disease is also known as Sly syndrome and named after William Sly, MD, who first recognized the disease in 1973. The disease is due to mutations in the GUSB gene that lead to reduced activity of beta-glucuronidase, an enzyme involved in the breakdown of glycosaminoglycans (GAGs).
The severity of MPS VII varies widely among affected individuals. The most severe form of MPS VII, or infant-onset MPS VII, is often characterized by hydrops fetalis, a condition in which excess fluid builds up in the body before birth. Most infants with hydrops fetalis are stillborn or die soon after birth. Individuals with later-onset MPS VII often begin to display symptoms of the condition during early childhood and may include: macrocephaly, hydrocephalus, macroglossia, hepatosplenomegaly, heart valve abnormalities, and umbilical or inguinal hernias. Furthermore, the airway may become narrow in some people with MPS VII, leading to sleep apnea. Often, for MPS VII patients, their cornea becomes cloudy, which can cause significant vision loss, and they may also experience recurrent ear infections and hearing loss. Affected individuals may also have developmental delay and progressive intellectual disability, although intelligence is unaffected in some people with this condition.
Skeletal abnormalities that become more pronounced with age, including short stature and joint deformities that affect mobility, are also fairly common. Individuals with this condition may also have dysostosis multiplex. Carpal tunnel syndrome develops in many children with MPS VII. MPS VII patients may also develop spinal stenosis in the neck, which can compress and damage the spinal cord.
MPS VII is an extremely rare condition, with only about 200 cases worldwide. Despite its rarity, an enzyme replacement therapy has been developed and approved to treat this condition.
To learn more about MPS VII and other rare metabolic disorders, visit checkrare.com/diseases/metabolic-disorders/