PC2097: When Recess Leads to a Rare Diagnosis: Mediastinal Vascular Malformation in the Setting of Systemic Disease

Introduction: Vascular anomalies range from nevus simplex to multisystemic malformations. While some can be classified as tumors or malformations, kaposiform lymphangiomatosis (KLA) has components of both. This is a complex case of a girl with an unusual presentation ultimately requiring the dedication of multiple subspecialists to reach a rare diagnosis.

Case Description: A 12-year-old female patient presented March 2018 with a large epidural hematoma after sustaining a low-velocity injury from a dodgeball requiring an emergent craniotomy. However, the degree of bleeding for the location and level of impact was unusual. She was found to be mildly thrombocytopenic and coagulopathic. Testing for an oncological origin of the thrombocytopenia was negative. Findings also included a Chiari type 1 malformation, subconjunctival capillary hemangioma, and retinal vessel tortuosity. Testing for COl4A1 gene mutations and Hereditary Hemorrhagic Telangiectasia were negative. She was discharged with outpatient follow ups.

In 2019, she was readmitted for suspected bacterial meningitis, and again found to have mild coagulopathy with thrombocytopenia and elevated d-dimer. MRI brain and spine showed concern for an underlying systemic process with bone marrow involvement, lymphadenopathy, and pulmonary fibrotic changes. Flattening of bilateral optic discs with increased conspicuity of bilateral optic nerves sheath fluid was noted, and she was started on acetazolamide, which improved her headaches. She underwent a bone marrow biopsy showing thrombocytopenia and eosinophilia, and a lymph node biopsy showing rare reactive giant cells with occasional histiocytes. BRAF mutation testing and evaluation by oncology for Langerhans cell histiocytosis were both negative. A new CT scan was obtained and mediastinal mass was seen. Biopsy of the mass showed widely dilated and thin-walled vascular spaces with flat endothelium. Per pathology, these findings are observed with cavernous hemangiomas.

Discussion: KLA is a newly described aggressive vascular anomaly with a high mortality rate. Patients typically present with respiratory symptoms, along with bleeding concerns such as hematomas, thrombocytopenia, or hemorrhagic effusions. Similar to our patient's initial presentation of an epidural hematoma via a low velocity injury. Malformations and tumors can be seen throughout the body including the mediastinum, bone, and viscera. KLA is frequently diagnosed based on pathological findings of spindled lymphatic endothelial cells clusters and malformed lymphatic channels. Regarding treatment, there has been some success with sirolimus and steroids. Our patient was started on both, and after a few months of treatment showed normalization of platelet levels, coagulation numbers, and improved pulmonary function tests. Her 2 year follow up imaging showed complete resolution.

Conclusion: Although KLA is rare, it is important to keep it in the differential due to the high mortality, especially when a patient presents with multisystem involvement and possible vascular anomaly. Advancements with targeted treatment and more awareness can lead to earlier diagnosis and hopefully more successful outcomes.