Baló disease (concentric sclerosis)

Balo disease (also written as Baló disease, Balo concentric sclerosis, or Baló concentric sclerosis) is a rare inflammatory demyelinating disease of the central nervous system that is generally considered a rare variant within the spectrum of multiple sclerosis (MS). It is characterized by distinctive concentric rings of alternating preserved and damaged myelin (the protective covering surrounding nerve fibers) within the brain, producing a characteristic “bull’s-eye” or layered appearance on magnetic resonance imaging (MRI).

Although Baló disease was once thought to be almost uniformly fatal and rapidly progressive, current evidence shows that its clinical course is more variable. Some people experience a single (monophasic) episode and recover with treatment, while others develop relapsing disease or later meet criteria for multiple sclerosis. Lesions most commonly occur in the brain but may also involve the brainstem or, less commonly, the spinal cord. MRI plays a central role in diagnosis and often allows recognition of the disease without the need for brain biopsy.

Headache, seizures, weakness or paralysis affecting one side of the body, muscle spasms, numbness or other sensory changes, speech difficulties (aphasia or dysarthria), cognitive impairment, behavioral changes, fever, and other neurological symptoms depending on the location of the lesions.

Baló disease is considered part of the spectrum of inflammatory demyelinating disorders of the central nervous system and may occur alongside or later evolve into multiple sclerosis. Because several neurological disorders can produce similar symptoms or MRI findings, healthcare providers may also evaluate for conditions such as myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), neuromyelitis optica spectrum disorder (NMOSD), acute disseminated encephalomyelitis (ADEM), tumefactive multiple sclerosis, brain tumors, abscesses, and lymphoma.

Baló disease is extremely rare. Although it occurs worldwide, it has been reported more frequently in Asian populations than in people of European ancestry. Most cases develop in adulthood, although pediatric cases have been reported. Current evidence does not clearly demonstrate a consistent difference in prevalence between males and females.