A malnourished person is usually very thin (although there are certainly cases of people who aren't thin, but still have nutritional deficiencies) and such a person may have any number of nutritional deficiency diseases. A person with a vitamin D deficiency can have a disease called rickets, which results in malformed bones. A vitamin C deficiency causes scurvy, which has many symptoms including bleeding gums. Vitamin B deficiencies cause beri-beri. Iron deficiencies cause anemia. Iodine deficiencies cause goiter (enlarged thyroid gland) etc.