Differentials
Bulimia nervosa
SIGNS / SYMPTOMS
Not significantly low in weight. (If significant low weight is present together with intermittent binge-eating and compensatory behaviours that aim to prevent weight gain, AN is the identified diagnosis.)
INVESTIGATIONS
Clinical interview or standardised assessment such as Eating Disorder Assessment for DSM-5 (EDA-5). Eating disorder assessment for DSM-5 (EDA-5) Opens in new window
Avoidant-restrictive food intake disorder (ARFID)
SIGNS / SYMPTOMS
No preoccupation with body shape or weight, no fear of fat; avoidant or restrictive eating is motivated by concerns other than body shape or weight such as sensory issues relevant to eating process (e.g., avoidance of foods with particular feel, taste, or smell), or concern about aversive consequences of eating, including fear of choking or vomiting.
INVESTIGATIONS
Clinical interview or standardised assessment such as EDA-5. Eating disorder assessment for DSM-5 (EDA-5) Opens in new window
Depression
SIGNS / SYMPTOMS
If mood has been associated with decreased appetite, intake, or weight, these symptoms generally improve quickly with antidepressant treatment.
If depression is associated with poor concentration and/or poor self-esteem, these features are not associated with nutritional status or weight change.
INVESTIGATIONS
Clinical interview or standardised diagnostic assessment such as the Structured Clinical Interview for DSM-5 (SCID). Structured Clinical Interview for DSM-5 (SCID-5) Opens in new window
Obsessive-compulsive disorder (OCD)
SIGNS / SYMPTOMS
OCD often presents similarly, with ritualised eating habits. However, OCD is also characterised by obsessions unrelated to food, such as a fear of contamination or of doing harm. Medication may be effective at decreasing obsessive thoughts in OCD, by contrast with the lack of similar benefit associated with medication in AN.[80]
INVESTIGATIONS
Clinical interview or standardised diagnostic assessment such as SCID. Structured Clinical Interview for DSM-5 (SCID-5) Opens in new window
Body dysmorphic disorder (BDD)
SIGNS / SYMPTOMS
Unlike eating disorders, BDD usually focuses on perceived flaws of the face or head.[81] When body image preoccupations involve an inaccurate perception of being overweight or an inaccurate belief that non-facial parts of the body (such as stomach or legs) are too fat, and if the patient has an eating disorder, these body image concerns are considered symptoms of the eating disorder rather than BDD. But if the patient does not have an eating disorder, these concerns count towards a diagnosis of BDD.
However, there is an unclear area of overlap between BDD and 'other specified feeding and eating disorder' (i.e., weight concerns that do not qualify for a diagnosis of anorexia nervosa or bulimia nervosa).
INVESTIGATIONS
No differentiating test available. Use the DSM-5-TR diagnostic criteria to distinguish between BDD and other disorders.[1]
Hyperthyroidism
SIGNS / SYMPTOMS
Weight loss associated with thyroid disturbance is generally accompanied by additional symptoms of tachycardia, heat intolerance, diarrhoea, tremors, or tremulousness.
INVESTIGATIONS
Thyroid function tests are notable for high thyroxine and low thyroid-stimulating hormone in hyperthyroidism.
Type 1 diabetes mellitus
SIGNS / SYMPTOMS
History of weakness or weight loss in diabetes mellitus is associated with high serum glucose levels.
INVESTIGATIONS
Plasma glucose is elevated.
Crohn's disease
SIGNS / SYMPTOMS
May have abdominal pain, bloody stools, and possibly arthritic pain in addition to weight loss. Patients do not avoid food for fear of gaining weight.
INVESTIGATIONS
Endoscopy with biopsy will show inflammatory tissue changes.
Ulcerative colitis
SIGNS / SYMPTOMS
May have abdominal pain, bloody stools, and possibly arthritic pain in addition to weight loss. Patients do not avoid food for fear of gaining weight.
INVESTIGATIONS
Colonoscopy with biopsy will show inflammatory tissue changes.
Systemic illness with weight loss (neoplasm, infection, autoimmune)
SIGNS / SYMPTOMS
Weight loss is generally unintentional and is not accompanied by fear of weight regain or body image disturbance.
INVESTIGATIONS
Assessments to help specify aetiology of systemic weight loss may identify its cause. Consequently, comprehensive medical evaluation is recommended when patient presents initially.
Pediatric acute-onset neuropsychiatric syndrome (PANS)
SIGNS / SYMPTOMS
Abrupt and dramatic onset (<72 hours) of new obsessive-compulsive symptoms or severely restricted food intake, with similarly severe and acute onset of at least two concurrent cognitive, behavioural, or neurological symptoms.
Presentation typically from age 3 years to the beginning of puberty.
Relapsing-remitting and episodic symptom course.
INVESTIGATIONS
Clinical diagnosis. Other diagnoses such as Syndenham chorea, systemic lupus erythematosus, or autoimmune encephalitis should be ruled out first.
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