Complex sentence: There are two types of NDM: permanent neonatal diabetes mellitus (PNDM) is a lifelong condition and transient neonatal diabetes mellitus (TNDM) is diabetes that disappears during infancy but may reappear later in life.
Split into simpler sentences: There are two types of NDM: permanent neonatal diabetes mellitus (PNDM) is a lifelong condition. Transient neonatal diabetes mellitus (TNDM) is diabetes that disappears during infancy but may reappear later in life.