Phospholipase C-Gamma 2 Activity in Familial Steroid-Sensitive Nephrotic Syndrome.

BACKGROUND: Familial Steroid-sensitive Nephrotic Syndrome (SSNS) is rare, complicating the identification of candidate genes. A recent population-based approach study of SSNS identified HLA-DQA1 and Phospholipase C-Gamma 2 (PLCG2) missense coding variants as candidate loci. PLCG2 is a signaling molecule regulated by phosphorylation and is critical for Ca2+ flux in cells of the immune system. METHODS: In order to detect a candidate gene for familial SSNS, we conducted an whole-exome sequencing in a pedigree consisting of two healthy parents, two non-identical twin brothers with SSNS, and a healthy young sibling. Flow cytometric assays were conducted to investigate the effects of the identified PLCG2 rare variants on B cell receptor-mediated PLCG2 tyrosine 759 phosphorylation, as well as on Ca2+ flux. RESULTS: Two missense rare variants in the PLCG2 gene were detected in the affected twins. An increase in tyrosine phosphorylation of PLCG2 as well as more rapid Ca2+ flux were noted in response to stimulation in the affected twins compared to their parents. CONCLUSIONS: Rare variants in PLCG2 segregated with disease in familial SSNS. Functional studies suggest the combined rare variants result in a gain of function in PLCG2 activity. Taken together, these results support PLCG2 as a possible candidate locus for familial SSNS.

Acute hemorrhagic edema of infancy: the experience of a large tertiary pediatric center in Israel.

BACKGROUND: Acute hemorrhagic edema of infancy (AHEI) is a rare leukocytoclastic vasculitis of the small vessels occurring at a young age and considered as a benign self-limited disease. Due to its low prevalence, there are limited data on the presentation and complications of this disease. METHODS: All computerized files of children who were hospitalized at a tertiary pediatric center due to AHEI over a 10 year period were reviewed. Clinical, laboratory and histopathological data were collected. RESULTS: Twenty-six patients were included in our study, accounting for 0.7 cases per 1000 admissions of children aged 2 years or less. Mean age was 12.9 months. More than two thirds of the children had preceding symptoms compatible with a viral infection. Upon admission, all patients presented with typical findings of a rash and edema. Edema was most profound over the lower extremities (73%). Concomitant viral or bacterial infections were found in six children. Skin biopsy was performed in six patients revealing leukocytoclastic vasculitis. Thirteen children (50%) had systemic involvement including joint involvement (n=9), gastrointestinal hemorrhage (n=4), microscopic hematuria (n=1) and compartment syndrome of the limb (n=1). The latter was diagnosed in a patient with familial Mediterranean fever. CONCLUSIONS: Our largest data series highlighted what is known regarding clinical and histological findings in children with AHEI. However, contrary to what was previously reported, we found a higher rate of systemic involvement. Although AHEI is a rare entity, pediatricians should be familiar with its presentation, management and our reported complications.