Footnotes

• Contributors MF, HS and NK designed the study. FN and SHT, performed biochemical analysis. FN and MF drafted the manuscript. ABC, IK and NT identified the cases presented, supplied the relevant clinical information and reviewed the article for accuracy. All authors revised critically the manuscript for important intellectual content, approved the final version as submitted and agree to be accountable for all aspects of the work.

• 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.

• Competing interests None declared.

• Patient consent for publication Not required.

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