Late-onset riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency (MADD): case reports and epidemiology of ETFDH gene mutations

Abstract

Background: Multiple acyl-CoA dehydrogenase deficiency (MADD) is a riboflavin-responsive lipid-storage myopathy caused by mutations in the EFTA, EFTB or ETFDH genes. We report a Chinese family of Southern Min origin with two affected siblings with late-onset riboflavin-responsive MADD due to a homozygous c.250G > A EFTDH mutation and review the genetic epidemiology of the c.250G > A mutation.

Case presentation: Both siblings presented with exercise-induced myalgia, progressive proximal muscle weakness and high levels of serum muscle enzymes and were initially diagnosed as polymyositis after a muscle biopsy. A repeat biopsy in one sibling subsequently showed features of lipid storage myopathy and genetic analysis identified a homozygous mutation (c.250G > A) in the ETFDH gene in both siblings and carriage of the same mutation by both parents. Glucocorticoid therapy led to improvement in muscle enzyme levels, but little change in muscle symptoms, and only after treatment with riboflavin was there marked improvement in exercise tolerance and muscle strength. The frequency and geographic distribution of the c.250G > A mutation were determined from a literature search for all previously reported cases of MADD with documented mutations. Our study found the c.250G > A mutation is the most common EFTDH mutation in riboflavin-responsive MADD (RR-MADD) and is most prevalent in China and South-East Asia where its epidemiology correlates with the distribution and migration patterns of the southern Min population in Southern China and neighbouring countries.

Conclusions: Mutations in ETFDH should be screened for in individuals with lipid-storage myopathy to identify patients who are responsive to riboflavin. The c.250G > A mutation should be suspected particularly in individuals of southern Min Chinese background.

Keywords: C.250G > A mutation; ETFDH gene; Epidemiology; Late-onset multiple acyl-CoA dehydrogenase deficiency; Lipid storage myopathy; Southern min population.

Fig. 1

Sequencing of the electron transfer flavoprotein dehydrogenase gene of the two patients (a) and their parents (b), showed the same missense mutation of c.250G > A (p.A84T) in exon 3, chr4–159,603,421. In patient 1 and patient 2, the mutation was homozygous while in their parents it was heterozygous

Fig. 2

Genetic epidemiology of the c.250G > A ETFDH mutation. Geographic distribution of the Southern Min population (highlighted in red); reported number of MADD case with confirmed ETFDH mutation; and the allele frequency of the c.250G > A ETFDH mutation among all reported ETFDH mutations in different regions of China and neighboring countries. The Southern Min people is believed to have migrated from middle China around Henan Province (origin) to the Southern Min region (first migration) over a thousand years ago, and further travelled to Southeast Asia and overseas in a second migration in the past centuries. Map downloaded and modified from Glottolog 4.1 edited by HMS, H&F, R& HPM, M/ CC BY https://glottolog.org/resource/languoid/id/minn1248.bigmap.html#3/23.63/115.88