HFMD is caused by intestinal viruses, transmitted from person to person primarily via the digestive tract, and has the potential to cause epidemics. The disease occurs year-round across all age groups, but it is most commonly found in children under 5 years of age. Common causative agents include Coxsackie virus A6, A10, A16, and notably Enterovirus 71 (EV71). Significantly, severe complications are often associated with EV71, causing serious conditions such as encephalitis-meningitis, myocarditis, and acute pulmonary edema, which can lead to death.

Clinical Progression Stages

Disease recognition should be based on clinical progression through four stages. After an incubation period of 3 to 7 days, the child enters the onset stage, lasting 1-2 days, with symptoms such as mild fever, fatigue, sore throat, anorexia, and diarrhea.

The full-blown stage lasts from 3 to 10 days and is when typical symptoms are most evident. The primary manifestation includes mucosal lesions in the form of red ulcers or blisters with a diameter of 2-3 mm on the gums and tongue, causing mouth pain and refusal to eat. Simultaneously, diverse lesions such as erythema or blisters appear on the palms, soles, knees, and buttocks, typically persisting for less than 7 days.

Medical staff must pay special attention to warning signs of neurological, cardiovascular, and respiratory complications, which usually appear early, from day 2 to day 5 of the illness. Among these, the startle reflex is the most important sign indicating neurological complications. Besides the typical acute form, the disease can present as a fulminant form leading to death within 24-48 hours, or an atypical form with unclear rash signs.

Paraclinical Tests and Confirmed Diagnosis

Regarding basic tests, white blood cell (WBC) counts are usually within normal limits. However, if WBC increases > 16 G/L, blood glucose increases > 160 mg% (8.9 mmol/L), or platelets increase > 400 G/L, these are often related to complications. To confirm the specific cause, RT-PCR or virus isolation is performed using specimens from the throat, blisters, or rectum.

During diagnosis, HFMD must be differentiated from other pathologies with similar manifestations. For mouth ulcers, distinguish from aphthous ulcers, which are deep and recurrent. For skin rashes, differential diagnosis includes viral rash, allergies, impetigo, chickenpox, or meningococcemia.

Clinical Classification: The Key to Treatment

Decision No. 292/QD-BYT classifies the disease into four grades, which serve as the most critical basis for treatment decisions.

Grade 1 is the mildest form, where the child only presents with HFMD rash and/or mouth ulcers. The disease progresses to Grade 2 when neurological complications begin. Specifically, Grade 2a is defined when there is a history of startle reflex less than 2 times in 30 minutes, fever lasting over 2 days, or high fever > 39°C accompanied by vomiting or lethargy. Grade 2b is more severe, with signs of startle reflex observed during examination, or a history of startle reflex accompanied by lethargy or tachycardia > 130 beats/minute. This group also includes symptoms of ataxia, limb tremors, nystagmus, limb weakness, or cranial nerve palsy.

Grade 3 manifests as severe autonomic nervous system dysregulation, with a pulse > 170 beats/minute, increased systolic blood pressure relative to age, sweating, or abnormal breathing. Finally, Grade 4 is a state of severe respiratory and circulatory failure with manifestations of apnea, cyanosis, acute pulmonary edema, or shock. Accurate grading enables physicians to timely transfer patients or implement appropriate intensive care protocols, thereby minimizing the risk of mortality.