Erythema infectiosum (fifth disease) is a childhood exanthem caused byBI9 parvovirus [1]. Fifth disease was named because it was the fifth pink-red rash of infectious aetiology to be described. The first recognized outbreak of this disease occurred in Germany and was described in 1889 by Tschammer, who considered it a form of Rubella [2]. Erythema infectiosum clinical features were noted well before the actual discovery of BI9 parvovirus. This virus was originally discovered in 1975 by Cossart et al and was subsequently linked to the rash of erythema infectiosum in 1983 [3].  BI9 parvovirus is asingle-stranded DNA virus that selectively infects human erythroid progenitor cells, with the globoside or P blood group antigen as the cellular receptor for the virus [4]. This disease is self limiting but various complications with B19 infection like arthritis, pure red cell aplasia, pure amegakaryocytic thrombocytopenia,transfusion transmitted infection, hydros details make the diagnosis important. This article presents a case report of erythema infectiosum and discussion of its clinical findings.

A 7 year old female child presented with fever mild to moderate fever for 3 days, erythematous maculopapular rash and myalgias. Erythematous maculopapular rash was sudden in onset and appeared after 2 days of fever initially on cheeks giving an appearance of slapped cheeks (Figure1), followed by trunk and extremities. On general physical examination, she was afebrile and her vitals were within normal limits. Systemic examination was normal. On local examination, there was severe tenderness in bilateral thighs and calves. On follow up examination, rash disappeared after 10 to 14 days.

Her hemogram showed hemoglobin of 9.6 g/dL, total leukocyte count of 9.7 × 103/μL with 67% polymorphs, 31% lymphocytes, 1% monocytes, 1% eosinophils, ESR was 50 mm/h and platelet count was 160 × 103/μL. Her serum LDH was 1155 IU/L, serum CPK 1366 IU/L, SGOT 41 IU/L and SGPT 38 IU/L. Her liver and kidney function tests and urine analysis were within normal limits. Her blood smear was negative for malarial parasite and blood culture was sterile. WIDAL and ASO titers were insignificant. CRP was within normal range (10.5 mg/dL). Serology for Rickettsia, dengue and HIV were normal. In autoimmune workup, antinuclear antibodies were negative. The results of microbiological tests showed B19V acute infection (positivity of B19V DNA by polymerase chain reaction amplification on blood and throat swab.

Erythema infectiosum is a unique exanthematous illness, facilitating clinical diagnosis. Sporadic cases of erythema infectiosum can be confused with illnesses of other etiologies such as scarlet fever and rubella. Less typical cases may require distinction from other viral exanthems such as those caused by enteroviruses, drug reactions, sunburn, collagen vascular diseases, and allergic responses to environmental substances [5]. Measles, rubeola, roseola infantum, and erysipelas should be considered [6].

Classic “slapped cheek” appearance of a child with erythema infectiosum

Parvovirus B19 (B19V) infection is wide- spread and associated with a heterogeneous clinical spectrum, ranging from asymptomatic to potentially life-threatening events, such as aplastic crisis in chronic haemolytic anaemia, hydrops fetalis, neurological diseases and arthropathy [7]. This infection usually causes erythema infectiosum (EI), a benign self-limiting disease characterized by typical cutaneous manifestations (slapped cheek appearance with perioral sparing followed by a diffuse maculopapular rash evolving to a reticular pattern) [8]. B19 infection should be considered in the differential diagnosis of patients with any kind of rash fever illness in children, E.I. is one of them. EI has a worldwide distribution, with school outbreaks in late winter and early spring. It affects primarily the 4-10-year age group. E.I. is characterized by confluent erythematous, edematous patches or plaques on the cheeks, with sparing of the nasal bridge and periorbital regions. The rash spreads to the trunk and extensor extremities, which undergo patchy clearing resulting in a lacy reticular pattern. Occasionally, mild prodromal symptoms precede the rash; these include low-grade fever, headache, pharyngitis, malaise, myalgias, nausea, diarrhoea, and joint pain.

Infected persons experience three overlapping stages: a "slapped-cheek" facial rash (Fig. 1), a lacy or reticular body rash, and an evanescence/recrudescence stage [5].

The first stage occurs 3-7 days after the prodrome and is characterized by the appearance of a bright  erythematous facial exanthem. Red papules on the cheeks rapidly coalesce in hours to form red, slightly edematous, warm, erysipelas-like plaques symmetrically on both cheeks [1]. This exanthem tends to spare perioral areas and the nasal bridge, resulting in the classic "slapped cheek" appearance. It is exacerbated by sunlight exposure, tends to be manifested more commonly in children than in adults, and typically fades in 2-4 days [9].

The second stage of the disease occurs 1-4 days after the facial exanthem and consists of an erythematous maculopapular rash on the trunk extending to thebuttocks and extremities [1]. At this time a central clearing of the rash results in a characteristic reticular pattern [10]. This reticular rash has proximal extremity emphasis and dorsal ventral spread. Although the disease is known as slapped-cheek disease, the reticular pattern is distinctly characteristic and may be its only manifestation [6]. This pattern typically fades in 1-2 weeks [1].

In the third stage, which may last 1-3 weeks, the exanthem fades and reappears in previously affected sites [1]. This may vary in relation to factors such as emotional upset, heat, and sunlight exposure [11]. The rash eventually fades without scarring.

During hospital stay, the patient was started on empirical antibiotics, but the symptoms did not resolve, moreover the blood culture was sterile, WIDAL and ASO titers were insignificant and, autoimmune workup was negative, clinical possibility of viral exanthem was considered. Further investigations revealed the causative agent of the disease. IgM ELISA was found to be positive for B19 specific IgM antibodies. Severe myalgia, edema and tenderness over calf muscles were suggestive of myositis. Serum LDH and CPK level were elevated. On the basis of these clinical features and investigations, the diagnosis of erythema infectiosum with myositis was made. Thus, we document a case of erythema infectiosum in a 7 year girl child who presented with classical slapped cheek appearance and lower limb myositis.

Rashes are common in urgent care and taking a careful patient history is important for proper diagnosis of the underlying cause.

The authors declare that they have no conflict of interest

No funding sources

The study was approved by the Civil Hospital Amb.

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