Abstract
Introduction Voltage-gated calcium channel (VGCC) antibodies are considered specific for Lambert-Eaton myasthenic syndrome (LEMS). However, VGCC antibodies have been reported in other groups of patients without LEMS.
Multiple acyl-CoA dehydrogenase deficiency (MADD) is a type of mitochondrial myopathy which can present with a late onset form.
We report a case of a patient with positive VGCC antibodies concurrently with a diagnosis of possible late onset MADD.
Methods Clinical information and results of investigations were obtained.
Results A 75 year old woman presented with a gradual onset of proximal weakness associated with dyspnoea.
There was no relevant past medical history and family history was unremarkable.
Apart from mild proximal weakness, rest of the neurological examination was unremarkable. Deep tendon reflexes were normal.
Acylcarnitine profile on multiple occasions showed a pattern consistent with MADD. Muscle biopsy showed mild mitochondrial changes.
VGCC antibodies were detected on 2 separate occasions (86 and 100 pM; Ref Range <30pM). CMAP amplitudes and repetitive stimulation was normal with no facilitation nor decrement found. Position emission tomography was unremarkable.
The patient’s symptoms were thought to be secondary to MADD, therefore was treated with riboflavin, Q10 and carnitine and described significantly improved proximal strength and function.
Conclusion It has been generally considered that the VGCC Ab has a high sensitivity and specificity for LEMS. However, in a study of 100 neuromuscular patients with elevated VGCC antibodies, only 6 patients were diagnosed with LEMS. This case illustrates the importance of applying appropriate clinical judgement with results of investigations.
