Neutral lipid storage disease with myopathy (NLSDM) is a rare autosomal recessive disorder caused by mutations in the PNPLA2 gene, leading to defective triglyceride hydrolysis and lipid accumulation in tissues. We report a 28-year-old Indian female presented with a 4-year history of progressive, asymmetric limb weakness, elevated creatine kinase (1000 U/L), and vitiligo. Muscle magnetic resonance imaging (MRI) revealed asymmetric fatty infiltration. Muscle biopsy showed subtle vacuolar changes; notably, oil red O staining was negative, a known limitation in formalin-fixed tissue. Whole-exome sequencing identified a novel, likely pathogenic homozygous frameshift mutation, c. 212del, in exon 3 of PNPLA2, absent in population databases (gnomAD, ClinVar) and classified as likely pathogenic as per American College of Medical Genetics and Genomics (ACMG) criteria (PVS1, PM2). This case underscores the phenotypic variability of NLSDM and expands the genetic spectrum of the disease in the Indian population, highlighting the critical role of genetic testing for definitive diagnosis-particularly when histopathological lipid staining is unrevealing.

Defects in Adipose tissue TriGlyceride Lipase (ATGL)-mediated myocellular lipid droplet (LD) lipolysis results in mitochondrial dysfunction of unknown origin, which can be rescued by PPAR agonists. Here we examine if ATGL-mediated lipolysis is required to maintain mitochondrial network connectivity and function. Moreover, we explored if the functional implications of ATGL deficiency for mitochondrial network dynamics and function can be alleviated by promoting PPARα and/or PPARδ transcriptional activity. To this end, we cultured human primary myotubes from patients with neutral lipid storage disease with myopathy (NLSDM), a rare metabolic disorder caused by a mutation in the gene encoding for ATGL. These myotubes possess dysfunctional ATGL and compromised LD lipolysis. In addition, mitochondria-LD contact, mitochondrial network connectivity, and mitochondrial membrane potential were affected. Using a humanized ATGL inhibitor in myotubes (cultured form healthy donors) revealed similar results. Upon stimulating PPARδ transcriptional activity, mitochondrial respiration improved by more than 50 % in human primary myotubes from healthy lean individuals. This increase in respiration was dampened in myotubes with dysfunctional ATGL. Stimulation of PPARδ transcriptional activity had no effect on mitochondria-LD contacts, mitochondrial network connectivity, and mitochondrial membrane potential. Our results demonstrate that dysfunctional ATGL results in compromised mitochondrial-LD contacts and mitochondrial network connectivity, and that functional ATGL is required to improve mitochondrial respiratory capacity upon stimulation of PPARδ transcriptional activity.

Neutral lipid storage disease with myopathy (NLSDM) is a rare genetic myopathy caused by mutations in the patatin-like phospholipase domain-containing protein (PNPLA2) gene. To date, the number of reported cases remains limited and the correlation between disease phenotypes and genotypes remains unclear. Our study presents eight NLSDM patients from a Chinese neuromuscular center, identifying two PNPLA2 novel mutations through next-generation sequencing. Demographic and clinical data, as well as information from muscle electrophysiological, imaging, pathological, and genetic analyses, were collected. Several patients in the cohort were found to have right upper extremity weakness as the initial clinical manifestation. Notably, the first patient with facial muscle involvement was reported in this series. Muscle histopathology revealed a characteristic accumulation of lipid droplets predominantly in type 1 muscle fibers, featuring type 1 fiber atrophy concurrent with type 2 fiber hypertrophy, which was systematically described first in a summary manner. This study prompted us to summarize abnormal clinicopathological features and explore the relationship between gene mutations and disease phenotypes in NLSDM.

Neutral Lipid Storage Disease with Myopathy (NLSDM) is a rare lipid metabolism disorder caused by impaired Adipose Triglyceride Lipase (ATGL) activity, leading to neutral lipid accumulation in various tissues. It typically manifests with progressive skeletal myopathy, with an onset of around 35 years. In addition, some patients develop cardiomyopathy and liver dysfunction. Herein, we report the molecular characterization of a 27-year-old Hungarian patient and his family in whom two severe PNPLA2 mutations led to complete loss of ATGL production in the patient's tissues. DNA sequencing revealed a nonsense (c.24G>A) and a frameshift mutation (c.798dupC) in the PNPLA2 gene. RNA analysis showed nonsense-mediated decay of the c.798dupC transcript, while c.24G>A was normally expressed in the patient. However, Western blot analysis did not detect ATGL protein production. From a clinical perspective, our patient exhibited pes planus, proximal muscle weakness of the lower limbs and elevated CK levels from the age of six. MRI and biopsy revealed lipid accumulation, and leukocytes showed Jordans' anomaly. The muscle weakness progressed, and cardiomyopathy and hepatic steatosis were also observed recently. The case highlights two severe PNPLA2 mutations leading to complete ATGL deficiency and an unusual early-onset myopathy in childhood.