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A 52-year-old woman presented to hospital for dyspnea that had been progressively worsening for the past 8 months. She had been referred by a rheumatology outpatient clinic. She told clinicians that her breathlessness tended to come on gradually, and became worse with physical activity and with exposure to cold weather.

On further questioning, clinicians learned that her dyspnea was accompanied by occasional episodes of dry cough and wheezing, and was partially relieved by the short-acting beta agonist salbutamol. The patient denied having chest pain, rhinorrhea, nose bleeds, fever, or sweating. She was troubled by joint pain, swelling, and morning stiffness. She had been diagnosed with rheumatoid arthritis in 2010, and with arthritis and lichen planus 5 years later.

Frequent exacerbations of her rheumatoid arthritis resulted in pain, swelling, heat, and tenderness affecting the small joints in her hand, as well as the elbow and knee joints.

Physical examination noted normal vital signs; the patient's blood pressure was 120/70 mm Hg, resting pulse rate was 80 beats per minute, respiration rate was 18 breaths per minute, and oxygen saturation was 96% on room air. Moreover, a chest examination revealed normal auscultatory findings.

Laboratory tests were notable for significantly elevated antinuclear antibody levels, indicating the presence of active disease. C-reactive protein and erythrocytes sedimentation rate levels were also elevated. Clinicians noted that results of an ECG were normal, while a complete blood count identified the presence of leukocytes. The rheumatologist had a clinical suspicion of a relapse in rheumatoid arthritis with lung involvement.

A high-resolution CT scan showed numerous, mainly pulmonary nodules in the lung parenchyma. An incidental finding of the scan was a well-circumscribed mass lesion (1.26 × 1.47 × 1.16 cm) that involved the crus of the right hemidiaphragm (Figure).

The mass had a density of –127 Hounsfield units, indicating fat density. Based on the clinical and radiological findings, clinicians diagnosed the patient with diaphragmatic lipoma.

The patient was currently taking corticosteroids, methotrexate, folic acid, and chloroquine to manage her rheumatoid arthritis. At a follow-up examination 3 months later, she reported that both her breathing difficulties and joint attacks had improved.

Discussion

Clinicians presenting this of an incidental discovery of a diaphragmatic lipoma in a woman with rheumatoid arthritis presenting to hospital with shortness of breath stressed the importance of avoiding misdiagnosis of these benign soft-tissue tumors.

Comprised of mature adipose tissue, lipomas are often located on the upper back, shoulder, and abdomen. Although age at diagnosis varies, 80% of patients are diagnosed between the ages of 26 and 65 years.

Lipomas are categorized based on their anatomical location. Superficial lipomas are less than 5 cm in size and are usually asymptomatic, but they may cause local pain and be tender on palpation.

Deep lipomas, which account for 1% of cases, tend to be comparatively larger and develop in unusual anatomical locations, such as the female vulva and the transverse colon. "Additionally, giant epicardial lipomas have been found compressing the right atrium and eyelid," the authors noted.

They cited a that suggested that MRI should be obtained for all soft-tissue masses that are deep to fascia or those >5 cm in subcutaneous tissue, since atypical lipomatous tumors -- which present as large deep fatty masses and carry a small risk of becoming malignant -- are histologically identical to well-differentiated liposarcomas; however, the latter are associated with "a markedly worse prognosis secondary to their anatomic location." The review also noted that masses without an isointense signal to subcutaneous may represent a sarcoma and should be biopsied before definitive treatment, while large deep lipomatous masses and liposarcomas should be referred to a sarcoma center.

The authors reviewed 34 other diaphragmatic lipoma case reports, with this case being the first to report on a patient with rheumatoid arthritis.

Among these case reports, women were more likely to be affected than men, at approximate rates of 57% and 43%, which may reflect a greater presence of body fat in women. Mean age at diagnosis was 58 years, and 88.6% of patients were older than 45.

Most diaphragmatic lipomas have a posterolateral location; 54% were reported to occur on the left side and 43% on the right side, and one case had a bilateral location. The authors noted that location of lipomas can often be attributed to the fact that the liver is located on the right side.

In addition, "it is essential to differentiate between a diaphragmatic lipoma and Bochdalek hernia by the presence of discontinuity of the diaphragmatic musculature in a Bochdalek hernia," they wrote.

Almost 70% of the lipoma cases -- 24 of the cases reviewed -- were asymptomatic and detected either through postmortem autopsy or radiological studies.

The remaining 11 cases reviewed (31.4%) presented with symptoms such as , hemoptysis, and back pain; symptom severity ranged from mild to severe, and a few had fatal complications, such as one patient "who died after an episode of severe vomiting due to a ruptured diaphragm in an area that harbored a lipoma," the authors noted.

"In our present case, we believe that there was no association between the diaphragmatic lipoma and the rheumatoid arthritis," they wrote. While diagnosis is important, unless the mass is causing symptoms, increasing in size, or of an undetermined nature, "most cases of diaphragmatic lipoma require observation," as opposed to surgical treatment, they added.

They pointed out that of the 35 cases, 19 were under observation with one fatal outcome, and 16 were mostly symptomatic patients whose lipomas were surgically excised.

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