Persistent fatigue of unexplained origin

Specialty: General.

• chronic idiopathic asthenia
• prolonged fatigue of unknown origin
• unexplained chronic fatigue

Why it occurs

• Low virulence or intracellular infections (chronic infection by Mycoplasma pneumoniae, Coxiella burnetii, or brucellosis in the chronic phase that stimulate the immune system in a subtle but constant way)
• Pain and fatigue processing disorder of the central nervous system (chronic fatigue syndrome or fibromyalgia in the oligosymptomatic phase of pain but high fatigue)
• Marginal deficiency of cobalamin (vitamin B12) or folic acid in lower borderline ranges without evident anemia (which alter nervous myelination and mitochondrial function in a subclinical manner)
• Central type sleep apnea or upper airway resistance syndrome (where intermittent nocturnal hypoxia destroys the architecture of restorative sleep)
• Chronic toxicity from heavy metals at low levels or constant occupational exposure to volatile organic solvents.

Initial workup

Complete blood count with manual smear, erythrocyte sedimentation rate (ESR), ultrasensitive C-reactive protein (CRP), serum levels of vitamin B12, folates, ferritin, thyroid profile, antinuclear antibodies (ANA), rheumatoid factor, serology for Brucella and HIV, and chest x-ray in two projections.

Standard management

• Avoid the empirical and indiscriminate use of centrally acting stimulants such as methylphenidate without a precise diagnosis
• Methylcobalamin — vitamin B12, 1000 mcg orally daily if borderline lower serum levels are confirmed for neurological support
• Folic acid (5 mg orally daily if there is proven marginal deficiency or suspicion of mild intestinal malabsorption).