Strange power comsuption into sleep mode
SOLUTION [by OP]

My problem was that the SD card module was consuming when it was controlled by a transistor and my Arduino board was into the sleep mode. So I wrote into the void setup() the digitalWrite(PIN, HIGH) statements where PIN represents all pins connected to the board that belong to the SD card module (DI, DO, CS, and CK pins), to enable the internal resistor of that pins. Then, I checked the power consumption and I reached less than 100 uA.