Atypical anorexia nervosa is an eating disorder in which individuals meet all the qualifications for anorexia nervosa, including a body image disturbance and a history of restrictive eating and weight loss, except that they are not currently underweight. Atypical anorexia qualifies as a mental health disorder in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), under the category Other Specified Feeding and Eating Disorders (OSFED). The characteristics of people with atypical anorexia generally do not differ significantly from anorexia nervosa patients except for their current weight.Atypical anorexia was not described in earlier editions of the DSM, which included a requirement that person to have a body weight no higher than 85% of normal. Patients with atypical anorexia were diagnosed with the DSM-4 qualification "eating disorder not otherwise specified" (EDNOS) until the DSM-5 was released in 2013. Prior to DSM-5, EDNOS made up the majority of eating disorders diagnoses, making it difficult to estimate the prevalence of atypical anorexia during this period.The term atypical anorexia was historically used to describe the restrictive eating habits of some people with autism. The DSM-5 superseded this term with the avoidant restrictive food intake disorder (ARFID) diagnosis.
The loss of function mutation results in a phenotype that is different from that of a gain of function mutation, and these phenotypes are associated with two different forms of type 4 hemochromatosis. Loss-of-function mutations are more frequent and are associated with type 4A hemochromatosis. These mutations lead to a defect in the localization of ferroportin. Gain-of-function mutations are associated with type 4B and lead to production of ferroportin that resists negative regulation by hepcidin.Unlike other forms of hemochromatosis, which have a recessive pattern of inheritance, type 4 is an autosomal dominant disorder. The dominant inheritance pattern occurs in hemochromatosis type 4 because ferroportin is multimeric. Consequently, mutant ferroportin can associate with wild-type ferroportin in multimers and interfere with the function of normal ferroportin proteins. Pathophysiology
In normal iron regulation, iron is absorbed in the intestine, and ferroportin transports iron from the cells of the intestinal lining into the bloodstream. Iron in the bloodstream is then bound by transferrin, which carries the iron to target cells. Iron is stored in cells and blood serum in a protein called ferritin. Reticuloendothelial macrophages, which can phagocytose red blood cells, are important in the iron recycling process. Ferroportin is upregulated in the reticuloendothelial macrophages after phagocytosis occurs so that iron from the degraded red blood cells can be released into the bloodstream and transported to other types of cells as needed. Hepcidin, a protein synthesized in the liver in response to iron or inflammation, is a regulator of ferroportin expression.