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Definition and Diagnosis of Chronic Fatigue Syndrome (CFS) in Children and Adolescents

Several case definitions can be used to diagnose CFS in adults. Examples include the 1994 International CFS Case Definition, the 2003 Clinical Canadian ME/CFS case definition, and the 2011 International Consensus Criteria for Myalgic Encephalomyelitis (ME). These three case definitions include a criterion that the individual must have had severe chronic fatigue for 6 or more months. While the 1994 International CFS Case Definition has been primarily used to diagnose CFS in adults, it is also used to diagnose children and adolescents. In 2006, the International Association of Chronic Fatigue Syndrome Pediatric Case Definition Working group developed a case definition specifically for children and adolescents with ME/CFS. This definition requires a 3-month duration of fatigue. However, many doctors treating children and adolescents may not feel comfortable making a final CFS diagnosis after only 3 months.

The 6-month criterion in CFS case definitions does not mean that evaluation and symptom management should wait. Evaluation to rule out other conditions should start as soon as possible, because there could be other illnesses or reasons that explain the fatigue and symptoms. There are multiple conditions under each bodily system. Here are some examples: endocrine (e.g., hypothyroidism), cardiac (e.g., myocarditis), allergic (e.g., allergic rhinitis/sinusitis), infections (bacterial, viral or fungal), and autoimmune conditions (e.g., rheumatoid arthritis, celiac disease).  It can often take months or years for an underlying disease to become evident. For this reason, patients may benefit from receiving intervention during the CFS-like stage where the duration of fatigue and the number of symptoms have not yet met CFS diagnostic criteria.

Doctors may consider the possibility of CFS when a child or adolescent experiences fatigue, and 4 or more of accompanying symptoms. These symptoms may include muscle or joint aches, sore throat, tender cervical or axillary lymph nodes, post-exertional malaise and fatigue, pain, and memory or concentration problems.

School absence and difficulties in completion of school assignments could be an indication of cognitive problems, which are commonly reported by CFS patients.

Further exams and tests are needed before a CFS diagnosis can be made. These include:

  • A detailed medical history, including a review of medications
  • A thorough physical and mental status examination to exclude medical conditions that can present with similar symptoms
  • Laboratory screening tests to help identify or rule out other possible causes of the symptoms that could be treated
  • Additional tests and/or consultations to follow up on results of the initial screening tests

For doctors, a number of factors can complicate diagnosing CFS in children and adolescents. For example:

  1. Children and adolescents cannot always accurately describe their symptoms or how they feel.
  2. There is no lab test or biomarker for CFS.
  3. Fatigue and other symptoms of CFS are common to many illnesses.
  4. The illness has an unpredictable pattern of remission and relapse.
  5. The type, number, and severity of CFS symptoms vary from person to person.
  6. Parents may describe their child’s symptoms differently from how the child describes his/her symptoms.

Doctors should be aware that CFS in children may result in school absence which may be mistaken for school phobia. However, unlike school phobia, inactivity due to CFS persists on the weekends and during holidays as it does during the school week. It is important to document children’s activity levels and worsening symptoms after physical or mental activities. Changes in participation in hobbies and social activities can help identify illness effects on daily activities.


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