Marasmus is a form of severe malnutrition disorder of protein energy deficiency characterized by loss of weight to less than 60% of the expected body weight for the age, muscle wasting, variable low temperature and so on. Commoner in children less than a year old but may also occur in malnourished adults. Kwashiokor on the other side is malnutrition disorder caused by protein deficiency which presents with most of the symptoms of Marasmus and additional edema. It's more common after 18months of age..
The sever wasting is marasmus and the oedematous one is kwashiorkor...both of them are classified under PEM (protein-energy malnutrition).