Scapuloperoneal spinal muscular atrophy (SPSMA) is a rare autosomal dominant disorder caused by heterozygous mutations in the transient receptor potential vanilloid 4 (TRPV4) gene. It is characterized by scapuloperoneal weakness and congenital contractures. Herein, we present two Polish SPSMA families harboring the same p.Arg269His mutation in TRPV4. In the first, the mutation was identified by direct Sanger sequencing of TRPV4 in the proband and then confirmed in other affected family members. For the second proband, clinical exome sequencing (TruSight One, Illumina) revealed the presence of the same de novo mutation. The mutation is known (HGMD, Clinvar) and was found not only in SPSMA individuals, but also in patients with Charcot-Marie-Tooth 2C. It is localized in a conserved protein region and predicted in silico to be pathogenic. The clinical spectrum observed in the first family was variable, although all members showed symptoms of skeletal dysplasia and mildly or non-progressive lower motoneuron disorder. The clinical presentation varied from mild (shortness of the clavicles with no sign of muscle weakness) to severe (hypotonia, severe congenital contractures, delayed motor milestones, short stature, global weakness and respiratory insufficiency). The proband from the second family, the first child of healthy young parents, presented with bilateral congenital talipes equinovarus, hypotonia and delayed motor milestones. At the age of five years, she was able to walk with calipers. In both families, EMG analysis revealed a neurogenic pattern, while her sensitive and motor nerve conduction velocities were normal. The SPSMA is characterized by an extremely variable clinical picture. We have observed an intrafamilial heterogeneity with a more severe phenotype in the following generations that is suggestive of anticipation.