Signs and symptoms
Mild or early cases of Pagets are asymptomatic, and so most people are diagnosed with Pagets disease incidentally during medical evaluation for another problem. Approximately 35% of patients with Pagets have symptoms related to the disease when they are first diagnosed. Overall, the most common symptom is bone pain. When symptoms do occur, they may be confused with those of arthritis or other disorders, and so diagnosis may be delayed. Pagets may first be noticed as an increasing deformity of a persons bones.Pagets disease affecting the skull may cause frontal bossing, increased hat size, and headaches. Often patients may develop loss of hearing in one or both ears due to auditory foramen narrowing and resultant compression of the nerves in the inner ear. Rarely, skull involvement may lead to compression of the nerves that supply the eye, leading to vision loss. Associated conditions
Pagets disease is a frequent component of multisystem proteinopathy. Advanced Pagets disease may lead to other medical conditions, including:

Osteoarthritis may result from changes in bone shape that alter normal skeletal mechanics. For example, bowing of a femur affected by Pagets may distort overall leg alignment, subjecting the knee to abnormal mechanical forces and accelerating degenerative wear. Heart failure is a rare, reported consequence of severe Pagets disease (i.e. more than 40% skeletal involvement). The abnormal bone formation is associated with recruitment of abnormal blood vessels, forcing the cardiovascular system to work harder (pump more blood) to ensure adequate circulation. Kidney stones are somewhat more common in patients with Pagets disease.
Salla disease (SD) is an autosomal recessive lysosomal storage disease characterized by early physical impairment and intellectual disability. It was first described in 1979, after Salla, a municipality in Finnish Lapland. Salla disease is one of 40 Finnish heritage diseases and affects approximately 130 individuals, mainly from Finland and Sweden. Presentation
Individuals with Salla disease may present with nystagmus in the first months of life as well as hypotonia, reduced muscle tone and strength, and cognitive impairment. The most severely impaired children do not walk or acquire language, but the typical patient learns to walk and speak and has normal life expectancy. The MRI shows arrested or delayed myelination. Genetics
SD is caused by a mutation in the SLC17A5 gene, located at human chromosome 6q14-15. This gene codes for sialin, a lysosomal membrane protein that transports the charged sugar, N-acetylneuraminic acid (sialic acid), out of lysosomes. The mutation causes sialic acid to build up in the cells.The disease is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome (chromosome 6 is an autosome), and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder. Diagnosis
A diagnosis of this disorder can be made by measuring urine to look for elevated levels of free sialic acid.