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Prolidase deficiency in an infant with an incidental finding of methaemoglobinaemia
  1. Chern Yan Tan,
  2. Easwari Kothandaraman and
  3. Arunabha Ghosh
  1. Metabolic Medicine, Royal Manchester Children's Hospital, Manchester, UK
  1. Correspondence to Dr Chern Yan Tan; chernyantan{at}


A 4-week-old boy presented to the hospital with symptoms of diarrhoea and vomiting initially thought to be due to cow’s milk allergy. He was discharged with extensively hydrolysed formula. The patient represented with worsening of symptoms with metabolic acidosis and was screened and treated for sepsis. However, his condition deteriorated further and he developed methaemoglobinaemia. He was transferred to the high dependency unit and was given two doses of methylene blue. Further investigations were carried out, including rapid trio exome sequencing, which identified a homozygous pathogenic Peptidase D (PEPD) variant (c.978G>A, p.(Trp326*)). This was consistent with a diagnosis of prolidase deficiency.

  • congenital disorders
  • metabolic disorders
  • genetics

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  • Contributors CYT, EK and AG have all reviewed the examined the patient and came up with this idea of writing a case report to highlight this condition and the learning points as outlined in the report. CYT has contributed to this report by gathering the necessary information, carrying out the literature search, writing up the report and referencing. EK has contributed to this report by giving suggestion on how to draft the report, reviewing previous papers, editing and making changes to the report. AG has contributed to the report by reviewing previous literature papers, editing the report and helped to provide the laboratory data.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.