Abstract: Objective To explore the clinical features of spinal muscular atrophy with congenital bone fractures- 2 (SMABF 2 ). Methods The clinical data of 2 newborns with SMABF 2 caused by ASCC 1 gene variation were retrospectively analyzed and the relevant literatures were reviewed. Results Two children were siblings with a 4 -year age difference, and the younger brother was the proband. They were admitted to the hospital due to postnatal respiratory distress, hypotonia and arthrogryposis multiplex congenital. Because of respiratory failure, two newborns were given mechanical ventilation support after birth. Two children had finger flexion deformity, hyperextension and contracture of bilateral wrist joint and knee joint and bilateral club-foot. Whole body X-ray images showed poor skeletal development, rarefaction of bone, thin and gracile ribs. The proband suffered a fracture of the left tibiofibula, and his older brother suffered a fracture of the middle part of the right humerus. The whole exon sequencing analysis of the proband showed a novel homozygous missense variation of c. 913 C>T (p. 305 His>Tyr) in the ASCC 1 gene (NM_ 0011988002 . 2 , OMIM: 616867 ), which was located at 10 Q 22 . 1 . Both parents are carriers of heterozygous variation. ASCC 1 gene variation has not been reported in China. Conclusion SMABF 2 is an autosomal recessive inheritance disease, and ASCC 1 gene variation is the pathogenic factor.

Key words: spinal muscular atrophy; congenital bone fracture; ASCC 1 gene variation