Overview: Diagnosis and Management of MLT
MLT is a clincopathologic diagnosis. The diagnosis correlates histopathologic findings in the reticular dermis with a clinical syndrome of refractory thrombocytopenia.[1,2,3] Classically, the reticular dermis demonstrates multiple vessels expanded by complex, papillary structures lined by endothelial cells. These cells have moderate eosinophilic cytoplasm, round nuclei, and inconspicuous nucleoli. Cytologic atypia is minimal, and dysplasia is very rarely observed, which helps distinguish this entity from malignant neoplasms, such as angiosarcoma.
Immunochemistry can be useful in the diagnosis of MLT, particularly to confirm that they are endothelial cells. The cells strongly stain for endothelial markers, such as CD31, CD34, and lymphatic vessel endothelial receptor 1. However, these stains are not specific for MLT, and the differential diagnosis is quite vast. Therefore, the diagnosis relies mostly on correlation of histologic features with clinical information.
The differential diagnosis includes many other clincopathologic syndromes and vascular neoplasms, including MIH, kaposiform hemangioendothelioma, blue rubber bleb nevus syndrome, glomangiomas, benign lymphangioendothelioma, and angiosarcoma. Glomangiomas and benign lymphangioendotheliomas tend to be singular and are not strongly associated with thrombocytopenia. Kaposiform hemangioendothelioma can lead to a consumptive coagulopathy (Kasabach-Merritt syndrome), but these lesions tend to be singular and large, and have a nodular microscopic appearance. Blue rubber bleb nevus syndrome and MIH can also present similarly clinically, but blue rubber bleb nevus syndrome has a distinct microscopic appearance, and MIH eventually regresses. Angiosarcoma is frankly malignant and often has notable cytologic atypia, a feature not seen in MLT.
The cause of MLT is still elusive. MLT is characterized by complex papillary endothelial cell projections within blood vessel lumens, which cause the characteristic skin and visceral lesions.[4,5] These projections lead to extensive platelet destruction from shearing and subsequently lead to refractory thrombocytopenia. The mechanism behind the development of the papillary endothelial projections is currently unknown, and it is uncertain whether the process is neoplastic or reactive.
In our case, pharmacologic intervention included prednisolone, aminocaproic acid, sirolimus, and intravenous immune globulin. During his first year of life, the infant was transfused with a total of 25 units of platelets and 33 units of packed red blood cells. Studies report that transfusions are unavoidable, yet are only minimally helpful. We saw the best response to sirolimus, but other reports have documented fair responses to long-term steroids; bevacizumab[7,9]; thalidomide; propranolol, prednisone, and aminocaproic acid; vincristine; and corticosteroid.
MLT has been diagnosed and described in only a few case reports or very small numbers of patients. The complexity of the disease and its wide, variable symptoms have led to misdiagnosis and decreased awareness among medical professionals. This rarity, along with the condition's unique pathologic features and an ongoing effort to find treatment, makes every diagnosed case a unique learning opportunity and addition to medical knowledge. Our case is unique owing to the early diagnosis, close follow-up, and response to treatment during the child's first year of life. Despite treatment, this child eventually developed blindness and still requires regular transfusions.
Acknowledgment: The authors would like to thank the pediatric gastroenterology, pediatric hematology-oncology, and pathology departments at Madigan Army Medical Center, Fort Lewis, Tacoma, Washington.
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Cite this: A Newborn With Cutaneous Lesions and Hematochezia - Medscape - Jun 12, 2017.