Spectrum of mitochondrial diseases in a tertiary referral centre in Hong Kong

Abstract

OBJECTIVE: This study set out to examine the spectrum of mitochondrial diseases in a tertiary centre in Hong Kong. DESIGN: Retrospective cohort study. METHOD: A retrospective medical record review was undertaken for all patients with mitochondrial diseases seen in a tertiary referral centre in Hong Kong from 1995 to 2011. Results: Thirty-three patients were included, 21/33 (64%) suffered from a well-defined mitochondrial syndrome. The commonest clinical syndrome was Leigh disease (n=9, 27%). Three had complex IV deficiency. Mutation in the SURF1 gene was found in one patient, one had complex I deficiency and one had combined complex I and IV deficiency. The second commonest syndrome was mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS, n=7, 21%). Only 2/7 carried the typical A3243G mutation. Of the non-syndromic patients, three had complex I deficiency and two had complex IV deficiency. One had a POLG gene mutation. Biochemically, 91% (n=30) did not have a consistently raised lactate, 2 (6%) did not have hyperlactataemia at all. One patient with Leigh’s syndrome only had hyperlactataemia after glucose loading. Further genetic analysis of most patients is in progress. Significant mortality was found among the cohort (n=8, 24%). All of those who were A3243G negative have survived (n=4) but all of those with an A3243G mutation died (n=2). CONCLUSION: Most patients with mitochondrial disease in this tertiary centre did not have a consistently high blood lactate. A high index of suspicion is necessary in order for clinicians to diagnose mitochondrial diseases.