Aplasia cutis congenita is a rare congenital condition, characterized by localized absence of epidermis, dermis, and in some cases, subcutaneous tissues. About 80% of the patients with aplasia cutis congenita have involvement of the scalp. Aplasia cutis congenita, not involving the scalp, appears to be linear lesions with a symmetrical pattern of distribution on the trunk and limbs. Most reported cases are sporadic, but a few cases have been reported to have familial occurrence. There is no unifying theory for the pathogenesis and etiology. Herein, we report a 1-day-old female infant and her 4-year-old sister with unilateral aplasia cutis congenita on their legs. No similar conditions and other associated congenital anomalies were found in their family. There was no sign of teratogenic causes, such as intrauterine infections, drugs or chemical agents.