Acaeruloplasminaemia is an autosomal recessive type of neurodegeneration with brain iron accumulation and disorder of iron metabolism caused by a mutation in the caeruloplasmin (CP) gene resulting in the production of dysfunctional caeruloplasmin.
Acaeruloplasminaemia is a very rare disorder, with one Japanese study estimating a prevalence of approximately 1 in 2 million 1. The disease affects a wide variety of age groups but tends to become symptomatic in adulthood 1.
Patients present with a classic triad of clinical features caused by iron accumulation in various organs:
- neurologic disease: movement disorders, ataxia, eventual cognitive impairment 2-4
- diabetes mellitus 2-4
- retinal degeneration: usually visual acuity is not affected but changes can be appreciated on fundoscopy 2-4
In addition to this classic triad, most patients also have iron deficiency anaemia which may or may not be symptomatic depending on its severity 2-4.
Acaeruloplasminaemia is an autosomal recessive disorder caused by a mutation in the CP gene on the long arm of chromosome 3 resulting in the production of dysfunctional caeruloplasmin 5,6. Caeruloplasmin normally has a role in oxidising ferrous iron into its ferric form, allowing it to be loaded onto transferrin after being released by ferroportin 5,6. In patients with acaeruloplasminaemia, dysfunctional caeruloplasmin results in dysfunctional transport of iron out of cells around the body, causing iron accumulation and subsequent damage within those cells and tissues 5,6.
This iron accumulation typically occurs in three locations 5,6:
- brain: typically in the basal ganglia, but can also occur in the thalamus, cerebral cortex, and cerebellum 5,6
- pancreas: typically affecting beta islet cells 5,6
- retina 5,6
In addition to these three locations, the liver is also commonly involved asymptomatically, as well as other organs such as the heart or kidneys which are less commonly affected 5,6.
In general, radiographic changes are appreciated in the brain and the liver 6-9.
CT may reveal abnormal hyperdensities in the liver and brain, typically in the basal ganglia 6.
MRI is the modality of choice for evaluating patients with acaeruloplasminaemia 7-9. Signal changes are most commonly described in the brain and liver, and include 7-9:
Being a more sensitive imaging modality compared to CT for this condition, an often more extensive disease is noted, particularly in brain imaging where not only are the basal ganglia involved, but signal changes are also appreciated in the thalamus, cerebral cortex, and cerebellum (especially the dentate nucleus) 7-9.
Treatment and prognosis
Treatment is with iron chelation therapy, using agents such as desferrioxamine 10. These agents have been shown to prevent progression of neurologic clinical features 10.
- other types of neurodegeneration with brain iron accumulation, such as:
- pantothenate kinase-associated neurodegeneration (PKAN): classically has the eye of the tiger sign on T2-weighted imaging 6
- infantile neuroaxonal dystrophy (INAD) / atypical neuroaxonal dystrophy (NAD): generally T2 hypointensities are accompanied with diffuse high signal intensity and atrophy of the cerebellar cortex 7
- neuroferritinopathy: classically has cystic components that appear as hyperintense on T2-weighted images 7
- multiple system atrophy with prominent Parkinsonian signs (MSA-P): T2-weighted hypointensities tend to be limited to the putamen 6
- hereditary or secondary haemochromatosis: T2-weighted hypointensities are rarely in the basal ganglia 6
- Wilson disease: also has decreased serum ceruloplasmin, but T2-weighted hypointensities are rarely seen, and usually, T2-weighted hyperintensities of the basal ganglia are seen instead 6,7
- superficial siderosis: T2-weighted hypointensities tend to be more marked with a predilection for specific infratentorial areas instead of the basal ganglia 6
- Huntington disease: T2-weighted hypointensities of the caudate may be seen, but there is also caudate head atrophy 7
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- 10. Miyajima H, Takahashi Y, Kamata T, Shimizu H, Sakai N, Gitlin JD. Use of desferrioxamine in the treatment of aceruloplasminemia. Annals of neurology. 41 (3): 404-7. doi:10.1002/ana.410410318 - Pubmed