Sirolimus was efficacious and well tolerated in these study patients with complicated vascular anomalies. Clinical activity was reported in the majority of the disorders.

Objectives To test the hypothesis that somatic PIK3CA mutations would be found in patients with more common disorders including isolated lymphatic malformation (LM) and Klippel-Trenaunay syndrome (KTS). Study design We used next generation sequencing, droplet digital PCR (ddPCR), and single molecule molecular inversion probes (smMIPs) to search for somatic PIK3CA mutations in affected tissue from patients seen at Boston Children’s Hospital who had an isolated LM (n=17), KTS (n=21), fibro-adipose vascular anomaly (FAVA; n=8), or congenital lipomatous overgrowth with vascular, epidermal, and skeletal anomalies syndrome (CLOVES; n = 33), the disorder for which we first identified somatic PIK3CA mutations. We also screened 5 of the more common PIK3CA mutations in a second cohort of patients with LM (n=31) from Seattle Children’s Hospital. Results Most individuals from Boston Children’s Hospital who had isolated LM (16/17) or LM as part of a syndrome, such as KTS (19/21), FAVA (4/8), and CLOVES (30/32) were somatic mosaic for PIK3CA mutations, with 5 specific PIK3CA mutations accounting for ~ 80% of cases. Seventy-four percent of patients with LM from Seattle Children’s Hospital also were somatic mosaic for 1 of 5 specific PIK3CA mutations. Many affected tissue specimens from both cohorts contained fewer than 10% mutant cells. Conclusions Somatic PIK3CA mutations are the most common cause of isolated lymphatic malformations and disorders in which lymphatic malformation is a component feature. Five PIK3CA mutations account for most cases. The search for causal mutations requires sampling of affected tissues and techniques that are capable of detecting low-level somatic mosaicism, because the abundance of mutant cells in a malformed tissue can be low.

Objective To examine the presentation characteristics of patients with kaposiform hemangioendothelioma (KHE) to describe the spectrum of disease and risk factors for Kasabach-Merritt phenomenon (KMP). Study design Retrospective review of 163 patients referred to the Vascular Anomalies Center at Children’s Hospital Boston for KHE between 1991 and 2009 identified 107 patients with sufficient data for inclusion. Results The prevalence of KHE in Massachusetts is approximately 0.91/100,000 children. KHE manifested in infancy in 93% of cases; 60% as neonates. Common presenting features included enlarging cutaneous lesion (75%), thrombocytopenia (56%), and musculoskeletal pain or decreased function (23%). Cutaneous KHE favored the extremities, especially overlying joints. In our cohort 71% developed KMP (11% after initial presentation), and 11% of patients lacked cutaneous findings. Retroperitoneal and intrathoracic lesions, though less common, were complicated by KMP in 85% and 100% of cases, respectively. Compared with superficial lesions, KHE infiltrating into muscle or deeper was 6.3 fold more likely to manifest KMP, and 18-fold higher if retroperitoneal or intrathoracic. KHE limited to bone or presenting after infancy did not manifest KMP. Conclusion An enlarging lesion is the most common presenting feature of KHE in infancy. Older patients with KHE or those lacking cutaneous manifestations present with musculoskeletal complaints or atypical symptoms. The risk of KMP increases dramatically when tumor infiltrates muscle or when KHE arises in the retroperitoneum or mediastinum.

Hemochromatosis is a progressive iron overload disorder that is prevalent among individuals of European descent. It is usually inherited in an autosomal-recessive pattern and associated with missense mutations in HFE, an atypical major histocompatibility class I gene. Recently, we described a large family with autosomal-dominant hemochromatosis not linked to HFE and distinguished by early iron accumulation in reticuloendothelial cells. Through analysis of a large pedigree, we have determined that this disease maps to 2q32. The gene encoding ferroportin (SLC11A3), a transmembrane iron export protein, lies within a candidate interval defined by highly significant lod scores. We show that the iron-loading phenotype in autosomal-dominant hemochromatosis is associated with a nonconservative missense mutation in the ferroportin gene. This missense mutation, converting alanine to aspartic acid at residue 77 (A77D), was not seen in samples from 100 unaffected control individuals. We propose that partial loss of ferroportin function leads to an imbalance in iron distribution and a consequent increase in tissue iron accumulation.

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Objective To describe the clinical and imaging characteristics of a new lymphatic disorder with a unique histological pattern and poor prognosis. Study design An observational, retrospective study identified and characterized 20 patients with distinct lymphatic histopathology referred to the Vascular Anomalies Center at Boston Children’s Hospital between 1995 and 2011. Results The median age at onset was 6.5 years (range, birth-44 years). Clinical and radiologic findings suggested a generalized process. The most common presentations were respiratory symptoms (50%), hemostatic abnormalities (50%), and an enlarging, palpable mass (35%). All patients had mediastinal involvement; 19 patients developed pericardial (70%) and/or pleural effusions (85%). Extrathoracic disease manifested in bone and spleen and less frequently in abdominal viscera, peritoneum, integument, and extremities. Despite aggressive procedural and medical therapies, the 5-year survival was 51%, and the overall survival was 34%. Mean interval between diagnosis and death was 2.75 years (range, 1 to 6.5 years). Conclusions We describe a clinicopathologically distinct lymphatic anomaly. We propose the term kaposiform lymphangiomatosis (KLA) because of characteristic clusters or sheets of spindled lymphatic endothelial cells accompanying malformed lymphatic channels. The intrathoracic component is most commonly implicated in morbidity and mortality; however, extra-thoracic disease is frequent, indicating that KLA is not restricted to pulmonary lymphatics. The mortality rate of KLA is high despite aggressive multi-modal therapy.

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We have studied the flexed-tail (f) mouse to gain insight into mammalian mitochondrial iron metabolism. Flexed-tail animals have axial skeletal abnormalities and a transient embryonic and neonatal anemia characterized by pathologic intramitochondrial iron deposits in erythrocytes. Mitochondrial iron accumulation is the hallmark of sideroblastic anemias, which typically result from defects in heme biosynthesis or other pathways that lead to abnormal erythroid mitochondrial iron utilization. To clone the f gene, we used positional cloning techniques, and identified a frameshift mutation in a mitochondrial transmembrane protein. The mutated gene, Sfxn1, is the prototype of a novel family of evolutionarily conserved proteins present in eukaryotes.