Primary cutaneous aspergillosis has been a rarely reported and suggested pathophysiology that requires a destruction of both mechanical and immunologic barriers (5). As part of the immunologic defense mechanism, macrophages destroy Aspergillus conidia, and polymophonuclear leukocytes and monocytes ruin Aspergillus hyphae through oxidate and nonoxidative process (5). Additionally, keratin and epidermal layer play the mechanical defense barrier role (5). Accordingly, the organism enters the injured skin by burns, surgical wounds, or sites of intravenous injection or catheter insertion (6). In this case, she denied any history of skin injury in the right hand. However, there could have been unnoticeable microtrauma. In addition, the patient had no any other symptom corresponding to pulmonary involvement or systemic pathology, and her chest CT exhibited no evidence of aspergillosis. These indirectly reflect primary cutaneous infection.
The cases of primary invasive aspergillosis of the hand have been documented in a few literatures and all reported patients were young children with malignant hematologic disease (3, 7-9). Primary aspergillosis in the hand of a rheumatoid arthritis patient with long-term use of immunosuppressive agents has never been reported yet. This patient has been taking steroid and methotrexate for a long time since diagnosed with rheumatoid arthritis 14 years ago and following immunodeficiency might attribute to aspergillosis.
Cutaneous lesions associated with Aspergillus typically present as erythema and induration such as in our patient, and it often resembles a hemorrhagic blister (3, 6). Hyphal invasion in an immunocompromised patient may lead to angioinvasion that induces ulcer and necrosis, further extension to adjacent osseous structure and soft tissue, and even hematogeneous systemic dissemination that could involve any organ (5, 6). Therefore, rapid diagnosis and treatment is important because poorly controlled infection may require amputation of the hand or aggressive systemic therapy, although early definitive diagnosis of apsergillosis remains difficult due to its nonspecific manifestations.
Although imaging findings of primary cutaneous aspergillosis of the hand has never been described, a multilobulated cystic lesion with diffuse enhancement of cystic walls and surrounding soft tissue on MR imaging gave the impression of infected multiple ganglion cysts in our case (10). In addition, rheumatoid nodule occurring in 20% - 30% of cases diagnosed with rheumatoid arthritis could be typically seen over the bony prominence or extensor surface of the upper extremity with possible combined infection (11). However, this patient presented no communication between the lesion and the joint capsule which could be often observed in cases of ganglion cysts or rheumatoid nodules (10, 11). Besides, rheumatoid nodule could be seen as low signal intensity on both T1 and T2 weighted images. Thus, it needs to be differentiated from the nodule showing central necrosis. Clinically, tuberculous infection was also suspected due to soft tissue mass containing cold abscess in the background of high endemicity of tuberculosis. Differential diagnosis between Aspergillus infection and tuberculous infection is hard, but the shape of the abscesses could be helpful. Aspergillus abscesses tend to have an irregular and thick wall, while, tuberculous abscesses usually have smooth and thin walls (12, 13). The wall of this lesion was thin and smooth, which was not correlated with previous report. However, central T2 hyperintensity of the lesion might be helpful in ruling out tuberculous infection because central caseous necrosis of tuberculous infection is mostly seen as isointensity or hypointensity on T1 and T2 weighted images (14, 15). The wall of the cystic lesion showed low signal intensity on T2 weighted images and intermediate to high signal intensity on T1 weighted images. Manganese, iron and magnesium in the fungal concretions may contribute to the low signal intensity on T2 weighted images, a finding similar to Aspergillus sinusitis and spondylitis (12, 16). Areas of high signal intensity on T1 weighted images may be found in Aspergillus abscesses as in our case because of the presence of iron, manganese, or methemoglobin in the lesion (16). Also, hemorrhage occurs frequently in the lesion approximately up to 25%, which could shorten the T1 relaxation times (16). Besides, multiloculated cystic lesion with enhancement of its wall and the adjacent soft tissue could be considered as infected hydatid cyst caused by Echinococcus. However, its soft tissue involvement is extremely rare as presented as 2.3% of patients living in endemic areas, and it also shows affinity for muscles at the root of the limbs due to its increased vascularity and decreased activity (17). This patient showed no evidence of daughter cell, floating membrane, or calcified wall that could be presented in case of echinococcosis.
This case is a rare case of primary invasive aspergillosis of the hand in a patient with long term use of an immunosuppressive agent. Invasive aspergillosis has a potential to induce catastrophic progress. Therefore, when a superficial multicystic mass in the hand of especially immunocompromised patients is encountered, invasive aspergillosis should be included in the differential diagnosis, although it is rare.
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