Homocystinuria, cblE Type (MTRR)
Homocystinuria, cblE type is a pan-ethnic autosomal recessive disorder caused by pathogenic variants in the MTRR gene. Individuals affected by this disorder will manifest symptoms early in childhood with failure to thrive, hypotonia, megaloblastic anemia, developmental delay, and cerebral atrophy with white matter abnormalities. Other symptoms also include homocystinuria and hypomethioninemia, and when untreated, the individual can also have abnormal eye movements, abnormal gait, and seizures. All symptoms are responsive to cobalamin treatment, making the prognosis favorable. Several specific variants have been associated with milder disease severity.
For information about carrier frequency and residual risk, please see the residual risk table.