According to your description, I think it should be "Polish syndrome". The following is the information I searched online. Polish syndrome, also known as pectoralis major defect and short finger syndactyly, occurs in the third week of upper limb embryo development. Typical syndrome groups include chest wall, spine and upper limbs malformation, and its incidence rate is 17000 ~ 165438. The ratio of male to female is 3: 1. The lesions of Pol syndrome mostly occur on the right side, accounting for about 75%, and there are also bilateral lesions. Its chest manifestations mainly include: the absence of major and minor muscles; 2 ~ 4 costal cartilage and anterior costal deformity; The latissimus dorsi, deltoid, supraspinatus and infraspinatus are all stunted to varying degrees. Women also include underdeveloped or underdeveloped breasts. Male patients can also see subcutaneous adipose tissue dysplasia. Common upper limb deformities include syndactyly and short finger. Most children have limb hypoplasia, but the degree is different, some fingers and phalanges are hypoplastic, some fingers are completely missing, and even the whole upper limb is hypoplastic. If there are no rib defects and abnormal breathing, there is no need for treatment. If you want to achieve a symmetrical shape, you can try breast augmentation surgery. In addition, it is useless because there is no pectoralis major exercise.