Differential Diagnoses for a 6-Year-Old with Signs of Autism and Food Obsession

Single Most Likely Diagnosis

• Prader-Willi Syndrome (PWS): Although the absence of macroglossia and serum glucose problems might seem to argue against PWS, it's crucial to consider that not all individuals with PWS exhibit all characteristic features. The food obsession and morbid obesity, especially at a young age, are highly suggestive of PWS. The syndrome is known for its association with autism spectrum disorder (ASD) symptoms, hyperphagia (an insatiable hunger), and significant obesity if food intake is not strictly controlled.

Other Likely Diagnoses

• Autism Spectrum Disorder (ASD) with Food Selectivity: Children with ASD often have restricted eating patterns or food selectivity, which can be mistaken for a food obsession. While this doesn't directly explain the morbid obesity, it could contribute to eating patterns that lead to weight gain if the selected foods are high in calories.
• Avoidant/Restrictive Food Intake Disorder (ARFID): This condition involves a lack of interest in eating or a fear of eating due to concerns over the taste, texture, or nutritional content of food. However, in some cases, it can manifest as an intense focus on specific foods, potentially leading to an imbalance in nutrient intake and obesity if those foods are high in calories.
• Food Addiction: Some research suggests that certain foods, especially those high in sugar and fat, can be addictive. A child who is morbidly obese and acts out when not given food might be experiencing withdrawal symptoms similar to those seen in substance addiction.

Do Not Miss Diagnoses

• Hypothyroidism: Although less common in children, hypothyroidism can cause increased appetite and weight gain. It's essential to rule out this condition due to its potential impact on growth and development.
• Cushing's Syndrome: This rare endocrine disorder can cause significant weight gain, among other symptoms. While it's unlikely, missing this diagnosis could have severe consequences due to its impact on multiple bodily systems.

Rare Diagnoses

• Leptin Deficiency: A very rare condition that affects the regulation of energy balance, leading to extreme obesity from an early age. It's characterized by an intense hunger and hyperphagia.
• McLeod Syndrome: A rare X-linked disorder that can lead to obesity, among other symptoms, due to its impact on the brain and other organs. However, its association with food obsession and autism symptoms is less clear.
• Bardet-Biedl Syndrome: A rare genetic disorder that can cause obesity, intellectual disability, and sometimes features of autism spectrum disorder. It's also associated with hyperphagia, which could explain the food obsession.

Each of these diagnoses requires careful consideration of the child's overall clinical presentation, including physical examination, laboratory tests, and behavioral assessments. A multidisciplinary approach involving pediatricians, psychologists, dietitians, and possibly geneticists will be essential in determining the underlying cause of the child's symptoms.