Homocystinuria is a rare congenital disorder of metabolism.
The disease may affect one or more of the systems below 1,2:
- eye: ectopia lentis
- CNS: seizures, dystonia, developmental delay
- skeletal: scoliosis, pectus excavatum, long limbs
- vascular: thromboembolism
A deficiency of the enzyme cystathionine-β-synthase causes classic homocystinuria whereby the metabolism of homocysteine to methionine is affected. It is inherited in a autosomal recessive fashion. Other forms of secondary homocystinuria can be seen in other rare inborn metabolism disorders (e.g. methylenetetrahydrofolate reductase deficiency) 1.
High levels of plasma total homocysteine and methionine are present 1. Neonatal screening heel-prick tests typically include testing for homocystinuria.
Genetic testing can be used to confirm homocysteinuria.
No radiographic features are specific for homocystinuria and the diagnosis is made through genetic and laboratory testing. Rarely, some associations of the disease may be visible on imaging (e.g. spontaneous pneumothorax or thromboembolism) 1-3.
Although not specific, MRI brain may show 4:
- multiple cortical-subcortical infarctions in the cerebellar and cerebral hemispheres of varying ages
- diffuse white matter signal intensity abnormalities may be present secondary to demyelination
- occlusive vessel or dural sinus disease on MR angiography or venography
- lens dislocation
Treatment and prognosis
Mortality in homocystinuria mostly occurs from premature cardiovascular disease 1.
- 1. Stephanie J Sacharow, Jonathan D Picker, Harvey L Levy. Homocystinuria Caused by Cystathionine Beta-Synthase Deficiency. (2017) Pubmed
- 2. Skovby F, Gaustadnes M, Mudd SH. A revisit to the natural history of homocystinuria due to cystathionine beta-synthase deficiency. (2010) Molecular genetics and metabolism. 99 (1): 1-3. doi:10.1016/j.ymgme.2009.09.009 - Pubmed
- 3. Yap S. Classical homocystinuria: vascular risk and its prevention. (2003) Journal of inherited metabolic disease. 26 (2-3): 259-65. Pubmed
- 4. Reddy N, Calloni SF, Vernon HJ, Boltshauser E, Huisman TAGM, Soares BP. Neuroimaging Findings of Organic Acidemias and Aminoacidopathies. (2018) Radiographics. 38 (3): 912-931. doi:10.1148/rg.2018170042 - Pubmed