[ZKKL] Academic Sharing | Common Viral Skin Diseases in Children — Measles, Hand-Foot-and-Mouth Disease, and Exanthem Subitum

Measles is a highly contagious acute infectious disease caused by the measles virus, characterized by fever, conjunctivitis, upper respiratory tract inflammation, and oral mucosal spots (Koplik’s spots). s Spot )  It is also characterized primarily by a generalized erythematous maculopapular rash. Before the introduction of the measles vaccine, with the exception of newborns who benefit from maternal antibodies for a brief period, everyone was susceptible, and the mortality rate was very high. Even with the use of the measles vaccine, more than 100,000 people worldwide still die each year, and in some developing countries, the mortality rate is even higher than… 5% Since the introduction of the vaccine, the epidemiological profile among susceptible individuals has become more complex, with an increase in cases among adolescents and adults. Furthermore, due to differences between vaccine‑induced immunity and naturally acquired measles immunity, 8 The proportion of cases among infants below a certain age has increased. Clinically, most measles cases present with very typical symptoms and signs, rash onset timing, sequence, and morphology; however, some patients exhibit atypical clinical features, giving rise to “atypical” forms of measles, such as hemorrhagic measles and herpetic measles. Meanwhile, severe complications—including bronchopneumonia, acute heart failure, encephalitis, and laryngitis—have markedly declined.

1. 1  Typical measles

Vaccination failures and unvaccinated infected individuals almost invariably present with classic measles, while approximately one-sixth of those who experience secondary vaccine failure also exhibit typical measles. The disease course can be divided into three phases.

1. 1 . 1  Prodromal period Generally 3 to 4d It primarily manifests as inflammation of the upper respiratory tract and conjunctivitis, with symptoms including fever, cough, sneezing, rhinorrhea, lacrimation, photophobia, conjunctival injection, and pharyngeal congestion; abdominal pain and diarrhea may also occur. After onset, 2  ~ 3d , approximately 90% The patient presents with measles enanthem on the buccal mucosa, opposite the first molars on both sides of the oral cavity, namely: Kop-lik's Macules—this serves as an important basis for early diagnosis.

1. 1 . 2  Rash phase The rash phase lasts 3 to … 5d . Typically, it occurs on the day of fever onset… 3  ~ 4  On the third day, a rash begins to appear when respiratory symptoms and body temperature reach their peak. The rash erupts in the following sequence: :  Behind the ears, along the hairline, on the forehead, face, and neck, the rash gradually spreads to the trunk and limbs, eventually reaching the palms of the hands and soles of the feet. 2  ~ 5d Reaches its peak. The rash initially presents as pale red maculopapules, with a diameter of… 2  ~ 4mm They are scattered, gradually increasing in number, and initially bright red; later, they coalesce into dark red, irregularly shaped or small patchy papules, with normal skin between the lesions. The rash is erythematous and blanches upon pressure. At the onset of the rash, systemic symptoms worsen, and body temperature may rise as high as… 40 Around ℃, there is conjunctival injection, photophobia, somnolence, and occasionally delirium. At the same time, respiratory symptoms worsen, with frequent coughing, redness, swelling, and pain in the pharynx, hoarseness, and cervical lymphadenopathy.

The gums are swollen, and the lingual papillae are erythematous, edematous, and enlarged, sometimes resembling the strawberry tongue seen in scarlet fever; the spleen may be mildly enlarged. During this phase, dry and moist rales are often auscultated in the lungs.

1. 1 . 3  Recovery period Approximately 10 to 14d , rash development 3  ~ 5d After reaching its peak, body temperature begins to decline, at… 12  ~ 24h The temperature returned to normal, the general condition improved rapidly, and the rash began to fade, with the order of resolution mirroring the sequence of onset. Following the resolution of the rash, mild brownish pigmentation remained, predominantly on the trunk, lasting approximately… 1  ~ 2  The disappearance of the rash is diagnostically valuable in the convalescent phase of measles. The rash lasts approximately… 2  The rash has completely resolved, with fine, bran-like scales visible locally.

1. 2  Special type of measles

1. 2 . 1  Mild measles Most cases result from partial immunity to the measles virus, such as in infants under six months of age, individuals who have recently received immunoglobulin, those previously vaccinated against measles, or persons experiencing a second episode of measles. Following infection, clinical manifestations are milder: fever and upper respiratory symptoms are less pronounced, measles enanthem is atypical or absent, the rash is sparse, the illness course is short, and complications are rare; however, the resulting immunity is comparable to that acquired after typical measles.

1. 2 . 2  Measles without rash In immunocompromised patients—such as those with leukemia, malignant tumors, congenital immunodeficiency, or who are receiving immunosuppressive agents—it may also occur in individuals who received passive immunization during the incubation period; some have been vaccinated against measles. 6  Within one to six months, the disease may also occur upon subsequent exposure to a measles patient or following another measles vaccination. Patients may present with fever, catarrhal respiratory symptoms, and atypical mucosal spots, but without a rash. If the patient develops severe complications such as acute encephalitis, diagnosis becomes considerably more challenging; therefore, confirmation must rely on epidemiological data and laboratory testing.

1. 2 . 3  Severe measles This type is commonly seen in young children who are malnourished, have weakened or deficient immune systems, or are suffering from other illnesses; it also occurs in patients with secondary bacterial infections or those who have frequent exposure to measles, making them prone to severe disease. The onset is abrupt, with high or extremely high fever, convulsions, a prolonged febrile course, recurrent seizures, rapid breathing, cyanosis of the lips and fingers, a weak and rapid pulse, marked signs of toxicity, and a severe rash that is dense, confluent, dark red, and coalesces into large patches (toxic measles). )  . Hemorrhagic rash may occasionally be observed, accompanied by visceral bleeding. (  Hemorrhagic measles );  Sometimes measles presents with a vesicular rash that may coalesce into bullae. (  Herpetic measles );  Sometimes the rash suddenly fades or fails to erupt fully, leaving behind a few bluish‑purple lesions; the complexion is pale or grayish‑blue, with severe systemic and respiratory symptoms, tachycardia, and cyanosis and coolness of the extremities—conditions often attributable to cardiac dysfunction or circulatory failure. (  Shock-type measles )  Such patients are often critically ill, with a high mortality rate.

1. 2 . 4  Atypical Measles Syndrome (atypical measles syndrome) Also known as atypical measles, this condition occurs when individuals who previously received an inactivated measles vaccine experience a marked decline in measles antibody levels after several months or years, followed by infection with the measles virus or a subsequent booster dose of the inactivated measles vaccine. It most commonly affects children aged 10 to… 24  In young adults, it is non‑contagious. Its pathogenesis remains incompletely understood; most researchers attribute it to a delayed hypersensitivity reaction to the measles virus. Clinically, its symptoms, the sequence of rash onset, and pulmonary manifestations differ from those of typical measles. The hallmark features of this form of measles are… :  The prodromal phase is atypical, with few symptoms such as fever and upper respiratory catarrhal signs, and often absent. Koplik's Spot ;  The rash typically begins on the distal extremities and gradually spreads proximally to the limbs, trunk, and face. ;  The rash differs from the typical form and may present as petechiae, maculopapules, vesicles, purpura, or urticaria, exhibiting polymorphism. ;  It is often complicated by pneumonia and pleural effusion, and pulmonary opacities may persist for several months to… 1  ~ 2  In this year, other complications are rare, and the prognosis is favorable. Diagnosis is based on a rise in measles antibodies during the convalescent phase, but isolation of the measles virus is not possible.

1. 2 . 5  Measles in newborns If a newborn’s mother lacks measles antibodies or has declining antibody levels, the infant may not receive sufficient protective antibodies from the mother. Moreover, if the infant has not yet reached the age for routine measles vaccination, active immunization remains unavailable. Should the mother become infected with measles during pregnancy or within a few days after delivery, or if the infant is in close contact with a measles case, neonatal measles can easily develop. Affected infants typically present with classic measles symptoms, including fever, upper respiratory tract inflammation, conjunctivitis, and a dense rash, often complicated by pneumonia. Treatment should include antiviral and antibacterial agents, with immune globulin therapy administered when indicated.

1. 2 . 6  Congenital measles If a pregnant woman develops measles before labor, the measles virus can cross the placental barrier, leading to intrauterine infection and resulting in congenital measles in the newborn. At birth, the infant exhibits diffuse measles‑like erythematous rash over the entire body and is prone to complications such as pneumonia and skin infections; intravenous immunoglobulin may be administered for treatment. During the course of measles, high fever and poor appetite can worsen the child’s nutritional status, potentially causing vitamin A deficiency, which may lead to corneal opacity and softening that progresses very rapidly, ultimately resulting in blindness. Supplementing with vitamin A is recommended. A It can prevent the occurrence of complications in infants with severe congenital measles.

1. 2 . 7  Measles during pregnancy In the early stages of pregnancy, measles infection can affect the nervous system, increasing the rates of both early and late miscarriage. Infections during the second and third trimesters are more likely to result in stillbirth and preterm delivery. Pregnant women who contract measles near term may transmit the virus to the fetus via the placenta, leading to neonatal measles.

1. 3  Complications

1. 3 . 1  Pneumonia Pneumonia secondary to bacterial or other viral infections is the most common complication of measles and may even lead to severe respiratory complications such as pneumothorax, emphysema, respiratory failure, or acute respiratory distress syndrome. It is also the leading cause of measles-related mortality, with most cases occurring during the rash phase.

1. 3 . 2  Laryngitis Mild laryngitis during the course of measles is one of its intrinsic manifestations and generally has a favorable prognosis. Secondary laryngitis, often caused by Staphylococcus aureus or β-hemolytic streptococcus, may, in severe cases, lead to asphyxia and death due to laryngeal spasm and airway obstruction.

1. 3 . 3  Cardiac dysfunction It is commonly seen in children under 2 years of age, with cardiac dysfunction resulting from measles viremia or complications such as pneumonia, high fever, hypoxia, and dehydration. A small number of patients may develop myocarditis or pericarditis.

1. 3 . 4  Liver damage In recent years, among measles complications, cases of liver injury have increased markedly compared with the past, predominantly affecting adult patients, with an incidence rate of 31% to… 86% . Hepatic injury is commonly observed during the acute phase of measles, that is, in the course of the disease’s 5  ~ 10  Heavens, liver function is mostly at… 2  ~ 4  Recovery typically occurs within the week, though in some patients it may persist for about six months.

1. 3 . 5  Encephalitis Encephalitis refers to inflammation of the brain parenchyma, with typical symptoms including fever, headache, and altered consciousness. Other manifestations may include disorientation, behavioral abnormalities, speech disturbances, hemiparesis, and seizures. It is the most common neurological complication of measles; however, because the clinical presentation of measles encephalitis is often nonspecific, it is frequently misdiagnosed. Vaccination can substantially reduce its incidence, and treatment is primarily symptomatic and supportive. Measles encephalitis encompasses the following four types.

1. 3 . 5 . 1  Primary Measles Encephalitis The incidence is approximately 1‰ to 2 ‰. Primary measles encephalitis typically occurs during the rash phase; its pathogenesis remains unclear. Current consensus attributes it to primary viral invasion of neuronal cells, followed by chemokine‑mediated recruitment and infiltration of lymphocytes. Measles virus RNA can be detected in the cerebrospinal fluid. NA It also tends to support this theory. Treatment is primarily supportive, with a mortality rate of approximately… 10% ~ 15% ， 25% This results in permanent neurological damage.

1. 3 . 5 . 2  Acute disseminated encephalomyelitis This encephalitis is mediated by immune mechanisms, with an incidence of approximately 1 per thousand among children with measles; it may also occur following measles vaccination, at a rate of approximately… 1  ~ 2 /ppm Acute disseminated encephalomyelitis is the most common central nervous system complication of measles virus infection, typically occurring on the … day after infection. 2  ~ 30  In clinical practice, it is often difficult to distinguish this condition from primary measles encephalitis. Its pathogenesis is primarily mediated by molecular mimicry, in which circulating antibodies target myelin proteins, leading to central nervous system dysfunction. Clinical manifestations include visual disturbances, urinary difficulties, and diminished reflexes. 1 /3 Patients may experience disease relapse, and their risk of progressing to multiple sclerosis is increased. Treatment primarily involves the use of glucocorticoids and intravenous immunoglobulin; the mortality rate in children is approximately 5% , the adult mortality rate is approximately 25%。

1. 3 . 5 . 3  Measles inclusion body encephalitis This encephalitis primarily occurs in immunocompromised children, typically within one year following measles infection or vaccination, and is characterized by psychiatric disturbances, motor dysfunction, and seizures. Due to the患儿… T Lymphocyte function is impaired, and the measles virus persists, but by… T Lymphocyte-mediated measles‑like rashes are either absent or very mild. At onset, cerebrospinal fluid (CSF) analysis is typically normal, or may show a slight increase in cells and protein; as the disease progresses, measles‑specific antibodies in the CSF gradually rise. Autopsy reveals that measles virus RNA can be detected in brain cells. NA Treatment is primarily supportive, and ribavirin may be effective. The mortality rate is approximately… 75%。

1. 3 . 5 . 4  Subacute Sclerosing Panencephalitis (subacute sclerosing panencephalitis ， SSPE) It is a chronic, fatal, neurodegenerative disorder caused by persistent infection of the central nervous system with a defective measles virus; mutations in the measles virus M gene are a major factor underlying this persistent infection. The incidence is approximately… 1 /25,000 However, the incidence may be higher in young children. The pathogenesis stems from the body’s failure to completely clear the virus during acute infection; over the first two years, viral mutations occur, leading to persistent infection and progressive deterioration. Neurological symptoms typically emerge following measles virus infection. 6  ~ 15  In this year, its pathogenic mechanism remains unclear. The characteristic pathological feature is intranuclear inclusion bodies. Clinically, the early manifestations include cognitive decline and mood changes, followed shortly by a distinctive rhythmic myoclonus; the electroencephalogram reveals periodic sharp‑wave complexes, and the cerebrospinal fluid… IgG There is an increase, with elevated levels of anti-measles antibodies in both serum and cerebrospinal fluid; by the late stage, cortical function is almost entirely lost. The disease progresses steadily, and patients typically, following onset, … 1  ~ 3  Deaths due to circulatory failure or secondary infection occurred annually, with a case-fatality rate approaching 100% Currently, there is no treatment for this disease that has been proven both effective and long-lasting; the mainstay of therapy is antiviral agents.

Along with symptomatic treatment, intraventricular injection of interferon-α combined with oral administration of inosine pranobex can lead to clinical improvement.

1. 3 . 6  Other Improper nursing care, inadequate nutrition, and poor sanitary conditions often lead to complications in patients, such as keratitis, corneal ulceration, stomatitis, otitis media, lymphadenitis, purulent conjunctivitis, enteritis, appendicitis, and meningitis. In children with immune deficiencies, severe or life‑threatening cytomegalovirus pneumonia may occur.