Radiological picture and HRCT findings
The basis of diagnostic imaging in lymphangioleiomyomatosis relies on identifying specific changes in the lung tissue. The classic and most reliable sign on high-resolution computed tomography (HRCT) is the presence of diffuse, thin-walled cysts. They are randomly scattered throughout all lung regions, with no marked predominance in any specific zone.
In addition to typical cysts, in rare cases, HRCT may reveal additional abnormalities:
- Interlobular septal thickening (interlobular septal thickening). This symptom occurs due to the expansion of lymphatic pathways. The cause is obstruction of pleuropulmonary lymphatic vessels or septal veins.
- Ground-glass attenuation (ground-glass attenuation). The appearance of such areas of decreased lung tissue transparency is presumably associated with episodes of pulmonary hemorrhage.
Differential diagnosis with Langerhans cell histiocytosis
When multiple pulmonary cysts are detected, one of the primary tasks for the radiologist is to differentiate LAM from Langerhans cell histiocytosis (LCH).
Main differences between lymphangioleiomyomatosis and LCH:
- Distribution of lesions: In LAM, cysts are distributed more diffusely, involving all regions. Unlike LCH, the basal lung regions do not remain spared (intact).
- Cyst morphology: LAM is characterized by a more regular, spherical shape of cystic lesions.
- Parenchymal status: The lung tissue between cysts in LAM appears unaltered, with no accompanying signs of fibrosis.
Pulmonary involvement in connective tissue diseases (CTDs)
Connective tissue diseases (Connective Tissue Diseases, CTDs) represent a broad group of chronic inflammatory and immune-mediated conditions. The lungs and pleura are highly vulnerable target organs in these states.
The detection rate of pulmonary lesions varies greatly depending on the criteria applied (histological, physiological, or radiological). It is important to understand that HRCT or radiographic findings are not strictly specific to a particular type of CTD. However, they play a crucial role as a factor supporting a complex clinical diagnosis. Furthermore, pulmonary pathology can occur either before or after the formal diagnosis of a specific CTD.
It is worth noting that interstitial lung diseases associated with CTD (CTD-ILD) have a more favorable prognosis than idiopathic pulmonary fibrosis (IPF).
IPAF syndrome (Interstitial pneumonia with autoimmune features) is a specific transitional category defined by international societies (ERS and ATS). The term is applied to patients with interstitial lung diseases who have serological or clinical signs of an autoimmune process, but insufficient to fulfill criteria for a definite CTD. IPAF criteria include morphologic, serologic, and clinical domains. Over time, the disease in such patients often evolves into a fully expressed connective tissue disease.
Rheumatoid disease and the lungs
Rheumatoid arthritis (RA) is closely associated with various pulmonary and pleural pathologies. Interestingly, the severity of respiratory tract damage does not correlate with the severity of the arthritis itself. In a significant number of patients, pulmonary manifestations present even before joint involvement.
Pleural involvement in RA is a frequent phenomenon, manifesting as pleural thickening or effusion. Effusions can be unilateral or bilateral (usually small to moderate in volume) and most often resolve spontaneously. Interstitial lung diseases in RA predominantly occur in smoking males with the seropositive variant of the disease.
Table: Intrathoracic manifestations of rheumatoid disease
| Abnormal | Features |
|---|---|
| Interstitial fibrosis | Most commonly follows the usual interstitial pneumonia pattern (usual interstitial pneumonia) |
| Pleural effusion / thickening | Usually small in volume, prone to spontaneous resolution |
| Bronchiolitis | Follicular or constrictive obliterative bronchiolitis may occur |
| Specific syndromes | Necrobiotic nodules (Caplan syndrome) |
| Other manifestations | Bronchiectasis, organizing pneumonia, as well as drug-induced lung injury due to methotrexate use |
Briefly: answers to topical questions
What interstitial pneumonia patterns, other than usual interstitial pneumonia, occur in systemic connective tissue diseases?
In systemic connective tissue diseases, besides usual interstitial pneumonia, non-specific, lymphoid, and organizing pneumonia patterns are observed.
- Non-specific interstitial pneumonia (NSIP) is one of the most frequent patterns in Sjogren's syndrome.
- Lymphoid interstitial pneumonia (LIP) is frequently seen in Sjogren's syndrome, and a lymphoproliferative disorder may develop on its background.
- Organizing pneumonia (Organising pneumonia) is identified as one of the intrathoracic manifestations of rheumatoid disease.
To easily distinguish LAM from LCH, remember: in LAM, the lungs are affected "globally and diffusely." That is, the cysts have a regular spherical shape, the basal regions are not spared (the entire lung is involved), and there is no fibrosis between the cysts.
Class and exam questions
What is the most frequent complication of lymphangioleiomyomatosis?
The most common complication is pneumothorax, which develops in about half of the cases due to the rupture of thin-walled pulmonary cysts.
What extrapulmonary pathology is most characteristic of LAM?
The most frequent abdominal finding in this disease is renal angiomyolipoma, a mass with a prominent fatty component.
What is IPAF syndrome?
This is interstitial pneumonia with autoimmune features. The diagnosis is made in patients who have signs of an autoimmune process that do not yet meet the full criteria for a systemic connective tissue disease.
Does the severity of pulmonary involvement in rheumatoid arthritis depend on the severity of joint involvement?
No, the severity of pleuropulmonary involvement in rheumatoid disease does not correlate at all with the severity of the arthritis itself.
What else to study on this topic
- Morphology and imaging features of renal angiomyolipoma
- Usual interstitial pneumonia (UIP) pattern on HRCT
- Radiographic appearance of Caplan syndrome (necrobiotic nodules)
- Differences between constrictive obliterative and follicular bronchiolitis
- Drug-induced lung injury (using methotrexate as an example)
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