Epileptic encephalopathy caused by biallelic mutation in PPM1D: a case report

Background: PPM1D gene encodes for metal-dependent protein phosphatase. Its function includes the inhibition of some tumor suppressor genes, DNA damage response, and cell cycle control. Germline heterozygous de novo mutations in this gene were reported to cause intellectual disability and hypotonia. Case Presentation: We report a 40-month-old girl with an intractable seizure disorder, microcephaly, and global developmental delay. She had frequent epileptiform discharges on electroencephalography. Molecular investigations showed a homozygous truncating mutation in the PPM1D gene. Both parents were healthy heterozygous carriers. Conclusion: This is the first time in the literature to describe a homozygous biallelic mutation in the PPM1D gene, which resulted in epileptic encephalopathy, microcephaly, and global developmental delay. PPM1D mutations could be inherited as autosomal recessive with asymptomatic heterozygote carriers.