Complex sentence: It is recognised as one of the rarer causes of sudden infant death syndrome (SIDS, "cot death" or "crib death"); although it is better described as a mimic, rather than a cause, of SIDS.
Split into simpler sentences: It is recognised as one of the causes of sudden infant death syndrome (SIDS, "cot death" or "crib death"). This condition is better described as a mimic, rather than a cause, of SIDS.