It is late in the summer when a 29-year-old Caucasian female, employed as a medical assistant in your foot and ankle clinic, presents with a two-day history of red spots on her feet. The red spots became small fluid-filled vesicles, which are present mostly on the soles. She says she has broken one of the small vesicles and it expressed a clear fluid.
The lesions are causing mild discomfort but are not very pruritic. Otherwise, she feels a little fatigued and reports a slightly elevated oral temperature today. Additionally, she reports a mild headache and a slight sore throat. She has experienced these symptoms for a few days but has not missed any work this week. She has not experienced any chills, nausea, vomiting, diarrhea, abdominal pain, joint pains or difficulty breathing.
She denies any out of state or foreign travel. However, she was visited last week by her sister and niece, who live in another state. The patient has had no known exposures to any new makeup, chemicals, paints, toxins, irritants or other potential allergens. She is taking birth control pills but denied taking any other medications, vitamins or supplements. No one else in her household or within her family had any similar conditions. She has never had similar signs or symptoms in the past that she can recall.
What The Exam Revealed
During the physical examination, we note several small tense vesicular lesions and a few small macules with an erythematous or mauve border on the plantar aspects of both feet. Careful examination also shows similar lesions on the hands. There are no targetoid lesions or any other distinctive skin lesions on the face, torso, arms or legs. There are also no color changes or inflammation involving the eyes or ears. The patient’s vital signs are normal except for a slight elevation of the oral temperature. The remaining portion of the physical examination is within normal limits and the patient has no other clinically significant skin conditions.
A Closer Look At Hand-Foot-Mouth Disease
The most likely diagnosis is hand-foot-mouth disease (HFMD). The disease is an acute, mild but moderately contagious viral infection, which is common in preschool children. Those with the disease are most contagious during the first week of the illness. This illness is usually caused by Coxsackie A16 but it can be caused by other Coxsackie viruses (A5, A7, A9, A10, B2, and B5 strains) as well as Enterovirus 71. Coxsackievirus is a subgroup of the enteroviruses and is a member of the family Picornaviridae. This family consists of small, nonenveloped, single-stranded RNA viruses. Most reported cases occur in summer and early autumn in temperate climates. However, cases can occur sporadically all year long.
Hand-foot-mouth disease is a self-limiting disease with resulting acquired immunity but a second episode can occur following infection with a different member of the Enterovirus group. This disease is most common in children under 10 years of age but one may see this with some frequency up until puberty. Adults can get it but this is much less common. When adolescents and adults are infected, their symptoms are generally mild because they have most often developed prior immunity. However, I have seen adults with HFMD who have presented with significant symptoms, probably due to a lack of exposure at an earlier age.
The usual period from initial infection to the onset of signs and symptoms (incubation period) is three to seven days. Fever is usually the first sign of HFMD. This is followed by a sore throat, malaise, abdominal pain and headache. In one or two days after the fever begins, the first macular lesions typically appear on the buccal mucosa, tongue or hard palate. These mucosal lesions rapidly progress to vesicles that erode and become surrounded by an erythematous halo. It is rare to see the original mouth lesions because they rapidly become ulcerated and resolve in about five days.
The early skin lesions on the hands and feet are usually round to elliptical, pink macules with a distinct mauve or purple border that follow within one or two days of the presenting mucosal lesions, and may persist for 10 days. When the lesions are elliptical, their long axis is parallel to the skin lines. The characteristic skin lesions proceed to vesicles that may be tender or painful if pressed. Approximately 75 percent of all patients with HFMD develop skin lesions of the palms and soles. Generally, the prognosis is excellent and complete recovery occurs in one week from the first presentation of symptoms.
Young children and workers in child care centers are especially susceptible to outbreaks of HFMD because the infection spreads by person-to-person contact with nose and throat discharges, saliva, fluid from blisters or the stool of an infected child. The virus can also spread through a mist of fluid sprayed into the air when someone coughs or sneezes.
A Guide To The Differential Diagnosis
Vesicular tinea pedis. This is a common misdiagnosis, especially in adolescents and adult patients presenting with HFMD. Vesicular tinea lesions are usually pruritic and do not usually ulcerate. The lesions of HFMD do not typically itch but may be tender or painful, and may ulcerate.
Palmoplantar pustular psoriasis. This chronic condition affects palms and soles, and may have periods of remissions and exacerbations. It is characterized by sterile pustules. New pustules are usually yellow and the older pustules are brown. This is in contrast to HFMD, in which tense vesicles are filled with clear fluid and they progress to painful ulcerations. Palmoplantar pustular psoriasis is strongly associated with cigarette smoking and is more common among females. This condition is difficult to treat effectively and one can diagnose it with a punch biopsy.
Classic erythema multiforme. This condition consists of targetoid eruptions affecting distal acral skin. It represents an immunologic reaction that most commonly occurs in cases of infection with herpes simplex. Central vesiculation may occur with erythema multiforme with formation of targetoid lesions which are lacking in this case of HFMD as is clinical evidence of an eruption of herpes simplex.
Dyshidrotic dermatitis (pompholyx). This is characterized by symmetric vesicular eruptions on the soles, palms or lateral aspects of the digits, which eventually become dry and crusted. Both surfaces of the palms and the soles may be involved simultaneously. Sharp demarcation at the wrists or ankles is common. Associated pruritus is intense in most reported cases. A clinical course of fluctuating exacerbation and remission is common. This is sometimes associated with weather changes and, in other cases, may be associated with emotional stress.
Varicella (chickenpox). This condition rarely involves the palms and soles. The lesions usually start on the face and scalp, and move toward the trunk areas of the body. Such a diagnosis would be unlikely in an otherwise healthy young woman.
Irritant contact dermatitis. This is much more prevalent on the hands and is less common on the feet, especially in the non-weightbearing areas. Primary irritant dermatitis results from direct contact to the skin. It affects individuals exposed to specific irritants and generally produces discomfort immediately following exposure. Healthcare workers may react to latex in examination gloves that provokes a contact dermatitis. Although irritant contact dermatitis is caused mostly by chemicals (such as acids, alkalis, solvents and oxidants), plants (such as hot peppers, garlic and tobacco) have also been implicated.
Lichen planus. The individual lesions of lichen planus may range from very discrete, individual lesions of 1 to 2 mm in diameter to larger, coalesced lesions of 4 to 5 mm in diameter. Typically, the lesions are described as polygonal, purple, pruritic, papules with a fine-mesh lacey pattern in the central lesion. Cutaneous lichen planus may involve the wrist and forearms, lumbar area, penis, anterior aspect of the lower legs, ankles and dorsum of the hands and feet. Lesions on the palms and soles are less common but do occur. In this region, they tend to be non-pruritic yellowish papules that usually lack the distinct morphology and characteristics of typical lichen planus lesions.
Scabies. The lesions of a scabies infestation may involve the hands and feet. They are usually very pruritic in nature, especially at night. Scabies may bite and burrow into the skin of the fingers, toes, palms and soles, and typical burrows of the female mite may be found by careful examination. Due to the intense pruritus, patient scratching excoriates many of the lesions.
Insect bites and stings. These may involve both the feet or hands, and cause significant pruritus. Most bites are on the dorsum of the hand and foot rather than the palmoplantar surfaces. In most cases, the reactions from bites are much more erythematous and inflamed with fewer vesicles than one would find with dyshidrotic dermatitis.
Key Insights On Prevention And Treatment
Preventive measures include good hand washing in children and adults, especially after using the toilet and changing a diaper, and before preparing food and eating. Routine disinfection of common areas with wipes or solutions with germ-killing alcohol is beneficial.
One may use other disinfectants, such as a diluted solution of chlorine-containing bleach (10% concentration), for cleaning shared toys. Doing so prevents the spread of infection to siblings or children within the same home or child care center. Blisters should not be ruptured as this allows for rapid viral spreading. Patients with HFMD should limit their exposure to others and children should be kept out of daycare or school until their fever is resolved.
There is no specific treatment for HFMD but general treatment is supportive and symptomatic for relief of fever, aches or painful mouth ulcers. Patients are advised to get sufficient rest, drink plenty of fluids and take over-the-counter pain relievers, such as acetaminophen or ibuprofen, if needed. Prevention of dehydration in babies and young children is essential, and one should not use aspirin in children under age 13.
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