Introduction: Spinal muscular atrophy (SMA) is the commonest cause of peripheral hypotonia in infancy. Clinically the diagnosis is made by the presence of weakness, areflexia, and tongue fasciculations in a floppy infant. We describe 4 children who presented with the clinical features of SMA but were diagnosed to have other disorders. Methods: We describe 4 young children (3 mo/male, 2 mo/male, 4 mo/male and 6 yr/female) who were clinically suspected to have SMA with peripheral hypotonia and areflexia. Two of these children had tongue fasciculations as well. Results: All the affected children had negative genetic studies for SMA. Whole exome sequencing revealed pathogenic variant in RRM2B gene in case 1, confirming the diagnosis of Mitochondrial DNA depletion Syndrome (MNGIE), D-bifunctional protein deficiency with HSD17B4 gene likely pathogenic at exon 20 in case 2, pathogenic variant in the gene MORC2 suggesting the diagnosis of Charcot-Marie-Tooth disease, axonal type 2Z in case 3, and pathogenic variant in CD59 gene, suggesting the diagnosis of hemolytic anemia, CD59 mediated, with immune mediated polyneuropathy in case 4. Immunotherapy with steroids was given in case 4. Conclusion: Negative genetic testing for SMA should prompt whole exome sequencing to diagnose such SMA mimics. This has important therapeutic, prognostic and genetic counseling implications.

Rohitha Jaikumar
Lady Hardinge Medical College
India

Leena Bharali
Lady Hardinge Medical College
India

Richa Gupta
Lady Hardinge Medical College
India

Suvasini Sharma
Lady Hardinge Medical College
India