Biotinidase deficiency is an autosomal recessive metabolic disease that causes biotin deficiency. The exact diagnosis of the lack of biotinidase is made by demonstrating the absence of enzyme activity in the serum. Biotinidase deficiency is treated with oral biotin taken for lifetime. Early diagnosis and treatment are very important and prevent a number of complications. In this case report, a newborn baby was referred for periodic healthcare assessments to a family medicine centre, where biotinidase deficiency was diagnosed. Screening performed as part of periodic health assessment in the primary care setting is important for the detection of certain diseases, as many disease-related disabilities can be prevented with early diagnosis. In family practice, “shared decision-making,” which represents one of the elements of the patient-centred clinical method, is very effective, provided that patients and their relatives adapt to preventive healthcare.