Dermatomyositis as a presentation of inflammatory lung pseudotumor

Introduction: Inflammatory pseudotumor (IPT) is a rare pulmonary neoplasm of uncertain etiology usually presenting as an asymptomatic radiographic finding. We describe a case of pulmonary IPT presenting as dermatomyositis (DM) with complete resolution following surgical resection. Case Presentation: A 48-year-old man was hospitalized with chest pain and elevated serum creatine kinase (CK). Two weeks prior he had been given prednisone 20 mg daily to treat a rash of recent onset. In the interim he had developed fever, generalized myalgia, arthralgia, and cough productive of yellow sputum. The chest radiograph and electrocardiogram were interpreted as unremarkable by the admitting physician (figure 1). The patient had a 25 pack-year smoking history and had mined coal for 20 years. Symptom review elicited chronic dyspnea on exertion, cough, and a recent 12 pound weight loss. The family history was significant for a sister with systemic lupus erythematosis. Examination revealed an ill appearing man with oral temperature of 100.2°F, pulse 104 per minute, and normal blood pressure. The skin revealed a generalized erythematous, macular rash involving the face, neck, chest, and the extensor surfaces of both hands. The heart was normal. The chest revealed fine bibasilar crackles without consolidation or rub. The muscles revealed mild generalized tenderness and mild weakness. The remainder of the exam was unremarkable. Laboratory evaluation revealed a leukocyte count of 13,900 per cubic mm, normal renal function, and elevated muscle enzymes: CK was 741 units per liter (range 55-200) with 100% MM fraction; lactate dehydrogenase was 305 units per liter (range 100-190); aldolase was 34.7 unit per liter (range 1.5-8.0). The Westergren sedimentation rate was 61 mm per hour. Cultures of sputum and blood and skin testing with PPD were all negative. A rheumatology consultant favored a diagnosis of DM and recommended a complete autoimmunity panel which subsequently returned negative. Intravenous antibiotics were given without improvement and upon re-review of the chest x-ray, a suspicious area of the left lung was noted. Computed tomography revealed a 3.5 cm left upper-lobe mass (fig 2 and 3). Pulmonary function revealed an FEV1 of 2.57 liters (79% predicted) but was otherwise normal. Bronchoscopy was unrevealing, and subsequent transthoracic needle aspiration was non-diagnostic. Concern regarding malignancy prompted surgical exploration. Infra-operative frozen section was inconclusive, and left upper lobectomy was performed. Immediate symptomatic improvement was noted in the post-anesthesia recovery room and complete resolution by day two; laboratory tests normalized by day 4. After outside referral, a final diagnosis of inflammatory pseudotumor was made. Discussion: This case describes a patient with clinical DM which promptly resolved after resection of a lung mass subsequently found to be IPT. Inflammatory pseudotumor is a rare entity commonly involving the lung that consists of a benign proliferation of cells that may mimic a primary tumor both radiologically and pathologically. The incidence of IPT is unknown; however, in one paper found it accounted for 0.7% of lung masses in a series of 1,075.¹ Pulmonary IPT usually presents as an asymptomatic chest x-ray finding; only 30% had complaints referable to the respiratory tract in one report.¹ Three series comprising 99 patients note the following symptoms: cough (11%), chest pain (10%), hemoptysis (9%), fever (7%), dyspnea (6%), recurrent respiratory infections (6%), and weight loss (6%).^2,3,4 Laboratory findings are non-specific and suggest an inflammatory process. Thoracic imaging typically reveals a mass lesion suspicious for malignancy. Because invasive procedures short of open biopsy do not reliably exclude malignancy, almost all cases are diagnosed by surgical excision. The diagnosis of DM rests upon the recognition of a specific pattern of skin involvement in the setting of myositis. Clinical suspicion may be supported by serologic testing: anti-nuclear and anti-Jo antibodies are positive in 60% and 25% of cases, respectively.⁵ Dermatomyositis may represent a paraneoplastic manifestion in 20% of cases, and occurs secondary to antibodies that react with skin and muscle. The causal relationship between DM and IPT in this case is strongly supported by the rapid resolution of the patient's signs and symptoms following resection. As the histology of the mass revealed mature plasma cells, it is provocative to speculate that these cells elaborated factors producing the dermatomyositis manifestations, much like the pathogenesis of a paraneoplastic syndrome. Conclusion: In summary, inflammatory pseudotumor is a rare cause of parenchymal lung lesions and herein is reported in association with DM. In addition to malignancy, benign inflammatory tumors should be considered when confronted with a DM-like syndrome in the presence of mass-like chest radiographic abnormalities.