Fig. 10
From: Essential neuromuscular advice for pathologists (first of two parts)
Spinal muscular atrophy diagnostic diagram (Oskoui and Servais 2023; Arnold 2018). 5q-Spinal Muscular Atrophy is caused in 96% of the patients by a homozygous deletion of the SMN1 (Survival Motor Neuron) gene that causes a loss of function of the SMN protein. It is a common hereditary cause of muscle weakness and arreflexia with neurogenic electroneuromyography. The diagnosis is confirmed by molecular studies and muscle biopsy is not required for diagnosis. mRNA: messenger ribonucleic acid