Background: Neutral lipid storage disease with myopathy (NLSD-M) is an autosomal recessive disease that manifests itself around the 3rd to 4th decade with chronic myopathy of proximal predominance in the shoulder girdle. Clinical myotonia is uncommon. We will report a rare case associated with pathogenic mutations on PNPLA2 and CLCN1 genes with a mixed phenotype of NLSD-M and a subclinical form of Thomsen’s congenital myotonia. Case presentation: We describe a patient with chronic proximal myopathy, very subtle clinical myotonia and electrical myotonia on electromyography (EMG). Serum laboratory analysis disclosure hyperCKemia (CK 1280 mg/dL). A blood smear analysis showed Jordan’s anomaly, a hallmark of NLSD-M. A genetic panel was collected using the NGS technique, which identified two pathogenic variants on genes supporting two different diagnosis: NLSD-M and Thomsen congenital myotonia, whose association has not been previously described. Conclusions: Although uncommon, it is important to remember the possibility of association of pathogenic mutations to explain a specific neuromuscular disease phenotype. The use of a range complementary methods, including myopathy genetic panels, may be essential to diagnostic definition in such cases.
Background Neutral lipid storage disease with myopathy (NLSD-M) is an autosomal recessive disease that manifests itself around the 3rd to 4th decade with chronic myopathy predominantly proximal in the shoulder girdle. Clinical myotonia is uncommon. We will report a rare case of association of pathogenic variants on PNPLA2 and CLCN1 genes with a mixed phenotype of NLSD-M and a subclinical form of Thomsen’s congenital myotonia. Case presentation We describe a patient with chronic proximal myopathy, subtle clinical myotonia and electrical myotonia on electromyography (EMG). Serum laboratory analysis disclosure hyperCKemia (CK 1280 mg/dL). A blood smear analysis showed Jordan’s anomaly, a hallmark of NLSD-M. A genetic panel was collected using next-generation sequencing (NGS) technique, which identified two pathogenic variants on genes supporting two different diagnosis: NLSD-M and Thomsen congenital myotonia, whose association has not been previously described. Conclusions Although uncommon, it is important to remember the possibility of association of pathogenic variants to explain a specific neuromuscular disease phenotype. The use of a range of complementary methods, including myopathy genetic panels, may be essential to diagnostic definition in such cases.
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