Autophagia is not classified as a mental disorder or a symptom

Symptom

A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...

 of a mental disorder in the Diagnostic and Statistical Manual of Mental Disorders

Diagnostic and Statistical Manual of Mental Disorders

The Diagnostic and Statistical Manual of Mental Disorders is published by the American Psychiatric Association and provides a common language and standard criteria for the classification of mental disorders...

(DSM), the diagnostic manual used in the United States.

Autophagia occurs when one is compelled to inflict pain upon oneself by biting and/or devouring portions of one's body. It is sometimes seen with schizophrenia

Schizophrenia

Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...

, psychosis

Psychosis

Psychosis means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...

 and Lesch–Nyhan syndrome.