When An Adult Patient Presents With Red Spots On The Feet
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.