A patient with mitochondrial trifunctional protein deficiency due to the mutations in the HADHB gene showed recurrent myalgia since early childhood and was diagnosed in adolescence

► MTP deficiency should be suspected in patients with recurrent muscular symptoms. ► It is important to repeatedly perform acylcarnitine analysis when attacks occur. ► The biochemical findings in MTP and VLCAD deficiency can overlap. ► Western blot and genetic analysis are useful to confirm the diagnosis.