PROS1 and hyperinsulinemic hypoglycemia, familial, 4: The findings indicated a PROS1 gene mutation (NM000313.3: C200A>C, C1493-17T>C) (Fig. 1D), a well-documented hotspot mutation associated with protein S deficiency [4], this discovery supported the diagnosis of protein S deficiency (PSD), attributing the patient’s thrombophilia to the identified genetic mutation.