Objective: Spinal muscular atrophy (SMA) are hereditary disorders characterized by weakness from degeneration of spinal motor neurons and caused muscle weakness and progressive loss of movement. SMA is an autosomal recessive disease caused by a genetic defect in the SMN1 gene. We aimed to analyze a family consisting of 4 members with an unclear situation regarding the inheritance – Autosomal dominant (?).  Methods: The family members have addressed in the Human Molecular Genetics Laboratory where underwent the clinical and molecular genetics evaluation. Clinically, electromyography; PCR and RFLP for molecular-genetic diagnosis.  Results: We have been etablished that mother (32 years) was presented symptoms of weak myopathy, molecular genetic analyzes showed deletion of 7 and 8 exon of the gene SMN1 in 5q chromosome, daughter (6 mounth) also with deletion 7 and 8 exon of the gene SMN1 in 5q chromosome but clinically with more serious symptoms, classical SMA. Quantity of copies of the pseudogene SMN has not been verified. Following the analyzes was revealed that the father and the other daughter are unaffected, and they are not heterozygous.  Conclusions: We describe a family with an unclear way of inheritance of a SMA disease, wich is usually autosomal recissive. In this case the mother and one of the daughters have been identified with deletion of exon 7 and 8 of the gene SMN in the 5q chromosome, this situation seems like an way of inheritance autosomal dominant for SMA.