Multidisciplinary detective work

1. Multidisciplinary detective work S Jarvis, (Pharmacy), A Bowron, V Powers (Clinical Biochemistry) and G Pierre (Paediatric Metabolic Medicine) Bristol Royal Hospital for Children

2. Case History • AB is a girl born in February 2009 • NICU for 2 weeks, hypotonia, and difficult feeding • 8 episodes of becoming floppy, eyes rolling, breathing difficulties • July 2009 needed increasing respiratory support • 27th July 2009 admitted to PICU for ventilation

3. Metabolic InvestigationsApril - September 2009 • Persistent lactic acidosis • Plasma amino acids normal • Urine organic acids showed • lactic acid • 3-methylglutaconic acid in 2 out of 6 samples • Muscle biopsy could not exclude mitochondrial DNA depletion syndrome

4. Treatment - September 2009 • Dichloroacetate (DCA) started • DCA interacts with the pyruvate dehydrogenase enzyme complex located in the mitochondria • Used for the treatment of lactic acidosis in patients with pyruvate dehydrogenase defects • Side effect profile includes polyneuropathy on prolonged use

5. November 2009 - a 2nd opinion • Repeat organic acid analysis showed markedly increased maleic acid and succinylacetone both toxic metabolites of the tyrosine metabolic pathway • Recommended starting nitisinone to remove the maleic acid and succinylacetone • ? Initial diagnosis of tyrosinaemia

6. Back in Bristol • Review of previous results • No succinylacetone in previous samples • Trace of derivatives in 2 samples • Liver Function and clotting normal • Tyrosine not increased • Clinical presentation not typical of tyrosinaemia • Nitisinone and low tyrosine diet started in November 2009 - initially for a short trial

7. Nitisinone • Nitisinone inhibits enzymatic activity blocking the formation of fumarylacetoacetate and succinylacetone • Nitisinone started based on a previously reported case in which “the morning after starting treatment ……. instead of just being able to walk with a wide-based unsteady gait, she could walk quite rapidly and steadily and could walk downstairs; a few days later she was able to run”

8. Further discussions • ? Did dichloroacetate exacerbate an underlying enzyme defect • Was the maleic acid also present in previous samples? • ? diagnosis of inherited deficiency of maleylacetoacetate isomerase (MAAI) • No abnormality was found on sequencing MAAI gene

9. Nitisinone Tyrosine degradation pathway Tyrosine 4-OH-phenylpyruvate Homogentisate Dichloroacetate Maleic acid Maleylacetoacetate Succinylacetoacetate X MAAI Fumarylacetoacetate Succinylacetone Fumarate Acetoacetate Porpho- bilinogen 5-ALA

10. Meanwhile - Another case? • A second patient underwent tests for metabolic disease and was also shown to have maleic acid in her urine. • On re-testing 2 months later this had disappeared without treatment • This patient was not on DCA and had a different presentation from AB • The clinical biochemist asked for information about her drug history as her notes were difficult to follow • After some investigation she was shown to have been previously prescribed domperidone for a short period

11. Following up on patient AB • A review of treatment was also undertaken for AB • Relevant findings • Age 4-6 months domperidone • Age 6-7 months amlodipine

12. Maleate salts • Used in several common drugs including • Domperidone • Amlodipine • Enalapril So were these the cause of AB’s metabolic findings?

13. Hypothesis • Could these patients have a polymorphism in a drug metabolising enzyme causing slow metabolism of maleic acid. • This would cause small increases in maleic acid • The addition of dichloroacetate in patient AB impaired MAAI activity resulting in a more marked increase in maleic acid

14. If so………….. Can we stop the low tyrosine diet and Nitisinone? • Decision made to stop both and to monitor clinical and biochemical changes

15. However, looking further • Both patients were given domperidone liquid which is base not maleate • Only some brands of amlodipine are maleate salts and we don’t have a record of which one was given to AB So we don’t have the evidence but……

16. Situation now • AB has stopped Nitisinone since November 2010 • No deterioration in clinical state • No return of maleic acid or succinylacetone • Markers of mitochondrial dysfunction still persist

17. AB • Clinically AB remains ventilator dependent and has just been discharged home with a “home ventilation” package • She continues on a metabolic cocktail of vitamins with no definitive diagnosis

18. Costs • £43,500 was spent on Nitisinone in the 12 months that AB was taking it • Biochemical monitoring cost approximately £4000 • Additional genetic testing

19. Lessons learnt for pharmacists • Organic acid abnormalities secondary to drugs, including salts, are common • A full drug history is needed when interpreting complex metabolic investigations • Liaising with clinical biochemists when test are being done will help to arrive at more accurate diagnoses

20. Benefits in this case were that • Patient has been able to stop a “lifelong” treatment • The trust and PCT have saved £43,500 a year for Nitisinone

21. Thank you To the team of clinical biochemists To the Metabolic service To the parents of “AB” for all their support