Background: Inosine triphosphate pyrophosphohydrolase (ITPase) deficiency associated with mutations in the ITPA gene is a recently characterized purine pathway defect that presents with early infantile epileptic encephalopathy and lethal course. This disorder is rare, and only 12 cases are reported worldwide.
Methods: We report two additional cases of ITPA-associated neurodegeneration and two pathogenic compound heterozygous variants. We also reviewed the previously published cases of ITPA-associated encephalopathy.
Results: Both cases presented with progressive infantile-onset encephalopathy, severe developmental delay, microcephaly, facial dysmorphism, and epilepsy. Together with the presented two cases, 14 cases were available for analysis. The mean age of presentation was 16.7 ± 12.4 months (range 3-48 m). The most common clinical features at presentation were developmental delay, seizures, microcephaly, and hypotonia, seen in all 14 (100%) patients. The mean age of seizure onset was 4.75 months (range 2-14 m). Cardiomyopathy was noted in 42% of patients where it was explicitly evaluated (n = 5/12). Consanguinity was reported in 77% of the cases. The cardinal neuroradiological features are T2-signal abnormalities and diffusion restriction in the long tracts, especially the posterior limb of the internal capsule and the optic radiation. The majority of the patients died before 4 years of age (85.7%).
Conclusion: ITPA-related encephalopathy presents with infantile-onset neurodegeneration, progressive microcephaly, and epilepsy. Progressive brain atrophy and diffusion restriction in the white matter tracts are important radiological clues.
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