3.3.1 Diagnostic Considerations
KLA is a rare yet very aggressive disease in which early diagnosis and
timely treatment are critical. KLA has only been recognized as a
distinct clinical entity since 2013 and unfortunately, is often
misdiagnosed [7]. Like GLA and GSD, KLA is inaccurately referred as
“lymphangiomatosis” but coagulopathy is the hallmark of KLA. In
patients with unexplainable hypofibrinogenemia, thrombocytopenia, and
bleeding, particularly if hemorrhagic ascites, pleural effusion, and/or
pericardial effusion are present, KLA must be considered. KLA commonly
involves bones and viscera and infiltrates into the thoracic and
abdominal cavities. When located in superficial soft tissues, KLA
appears as non-discrete red-purple purpuric lesions. The most common
presenting clinical features of KLA are bleeding and respiratory
symptoms such as cough and dyspnea [7].
Imaging is important for diagnosis of KLA, particularly since biopsy is
often unable to be performed safely. MRI imaging of the chest, abdomen,
pelvis, and total spine. High resolution chest CT may provide additional
information for lung or mediastinal involvement. Pleural and pericardial
effusions, along with LM involvement of the thoracic cavity, spleen and
bones are common. Similar to GLA, the osteolytic bone lesions are
cortex-sparing and involve multiple non-contiguous bones, most commonly
the vertebrae [7]. On imaging, KLA of the soft tissue appears as an
infiltrative abnormality on fluid-weighted MRI sequences, frequently
with stranding of the adjacent subcutaneous fat [24]. On
contrast-enhanced CT, KLA appears as infiltrative low-density
soft-tissue thickening or mass, and effusions are of low attenuation.
KLA is heterogeneously hyperintense on fluid-weighted MRI sequences,
with moderate to intense post-contrast enhancement and follows the
lymphatic distribution along bronchovascular bundles (Figure
4A) . Soft tissue thickening around the blood vessels and airways in the
anterior mediastinum and interlobular septal thickening are also
frequent findings (Figure 4B) . In viscera, KLA appears as
hyperintense round lesions on fluid-weighted MRI sequences and hypodense
lesions on CT. Enhancing infiltrative soft tissue is also frequently
seen in the retroperitoneum and abdomen [24]. Echocardiogram is also
indicated to evaluate for pericardial effusion.
If a soft tissue component is present, biopsy may be possible, depending
on severity of coagulopathy. If KLA is confirmed by pathology,NRAS testing of the tissue specimen should be considered to guide
therapy [10]. In our patient, a somatic NRAS Q61R mutation
with an allele frequency of approximately 5% was found in her splenic
tissue.