History
    A 39-year-old male smoker presented with productive cough for 3 days.  He complained of severe headache and fever of abrupt onset 7 days ago, followed by erythematous papules on the face and body.

Findings
     Initial chest radiograph shows diffuse reticulonodular or prominent nodular opacities predominantly in the both lower lung zone. Follow-up chest radiograph 10 days later shows marked resolution of the opacities. High-resolution CT scans of the same day with follow-up chest radiograph reveals 2 - 5 mm sized peripheral nodules, which are random in distribution through the both lower lung zones.

Discussion
     Chikenpox [primary Varicella Zoster virus infection] is a highly contagious, predominantly mucocutaneous disease. The incubation preiod averages 14 days (range 3 to 21 days). The overall incidence of pneumonia in patients with chickenpox appears to be about 14 %, but in adults admitted to the hospital it may be as high as 50%. About 90% of affected patients are aged 19 years or over, and over 75% of cases occur in the third to fifth decades of life. This high incidence of pneumonia in adults with chickenpox is in contrast to the lower incidence of varicella itself in this age group - 50% of cases occur in children under 6 years of age and only 19% occur in adults.
     In both adults and children, pre-existing neoplastic disease, particularly leukemia and lymphoma, and corticosteroid and broad-spectrum antibiotic therapy predispose patients to primary varicella pneumonia. Smoking history is another risk factor. The clinical manifestations of chikenpox pneumonia exhibit a wide spectrum from asymptomatic, through mild illness to death, with a recorded mortality of between 11 and 20%. The incidence of pneumonia is much higher in pregnant women and chickenpox pneumonia appeared to be a more serious illness in pregnancy, but mortality is similar to that in non-pregnant patients.
     In chickenpox, viremia develops promptly following deposition of the virus in the upper respiratory tract. Replication of disseminated virus then occurs within the reticuloendothelial system and, when host defenses are overwhelmed, a second viremia occurs with dissemination to mucocutaneous sites and the appearance of the characteristic rash. Vesicles similar to those on the skin and mucous membranes may also be seen in the trachea and larger bronchi and on the pleural and peritoneal surfaces.
     Acute chickenpox pneumonia is most common in adults with severe cutaneous manifestations of the disease. Symptoms, signs, and roentgenographic changes develop 2 to 3 days after the appearance of the vesicular eruption, and in most cases there is a history of contact with an affected child 3 to 21 days before onset of the acute illness. The onset often is marked by high fever, which may precede the rash by 2 to 3 days, in which was noted in this patient. In approximately one third of cases the white cell count exceeds 10,000 per cu mm and is associated with polymorphonuclear leukocytosis. Complement-fixating, neutralizing, and fluorescent antibodies are found in both varicella and herpes zoster infections, from about the fifth day of illness.
     The roentgenographic pattern is patchy, diffuse, airspace consolidation or nodular / miliary-like densities. The acinar shadows usually are fairly discrete in the lung periphery but tend to coalesce near the hilar and in the lung bases. In a minority of cases the changes have been described as transitory, some areas of air space consolidation clearing while new areas appear. Hilar lymph node enlargement may be present. Roentgenographically demonstrable pleural effusion is very uncommon and never large. Roentgenographic clearing may take from 9 days to several months. Remote chickenpox infection is characterized roentgenographically by wide spread micronodular calcifications with an average diameter of 2 mm scattered randomly and without confluence throughout the lung parenchyma. Histologically, they are composed of an outer, often lamellated fibrous capsule frequently enclosing areas of hyalinized collagen or necrotic tissue. Calcification is variable in intensity. In a case report done by Picken, CT revealed multiple small peripheral nodules of soft tissue density containing no calcification, mimicking metastatic lung disease.
     In this patient, laboratory findings were WBC count of 10360/ml and 1:64 cold agglutinin test. Skin Tzanck test revealed positive for multinucleated giant cells. Varicella Zoster IgG and IgM were positive. This patient and his son contracted chickenpox from his nephew whose chikenpox rash had developed several days before his illness.
     Given this patient's clinical manifestation, history of contact with chickenpox patient, radiographic findings and spontaneous resolution of the disease, the diagnosis would not be difficult.

References
1. Triebwasser JH, Harris RE, Bryant RE, Rhoades ER.  Varicella pneumonia in adults. A report of seven cases and a review of the literature. Medicine 1967;46:409-423
2. Esmonde TF, Herdman G, Anderson G.  Chickenpox pneumonia:  an association with pregnancy.  Thorax 1989;44:812-815
3. Rogerson SJ, Nye FJ, Beeching NJ. Chickenpox pneumonia:  an association with pregnancy [letter;comment on Esmondes TF]. Thorax 1990; 45:239
4. Picken G, Booth AJ, Williams MV.  The pulmonary lesions of chickenpox pneumonia-revisited.  Br J Radiol 1994;67:659-660
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6. Gatnash AA, Connolly CK.  Fatal chickenpox pneumonia in an asthmatic patient on oral steroids and methotrexate.  Thorax 1995;50:422-423