Hereditary fibrosing poikiloderma (POIKTMP syndrome) report of a new mutation and review of the literature.

Hereditary fibrosing poikiloderma with tendon contractures, myopathy, and pulmonary fibrosis (POIKTMP) is a genodermatosis with autosomal dominant inheritance caused by mutations in FAM111B. We report another case with a new pathogenic variant and analyze all previously published 34 cases with a focus on sequence of clinical presentation and genotype-phenotype correlation. POIKTMP is characterized by marked age-dependent clinical expressivity. FAM111B encodes a catalytic nuclear protein, expressed in many tissues, which contributes to impaired DNA repair affecting multiple systems. Specific inhibition of catalytic activity might be a future strategy to halt progression of this otherwise untreatable disease. Given the relentless progression of the disease, it would make sense to start such treatment as early as possible. In order to achieve this objective, children with suspected POIKTMP should therefore undergo early imaging of all relevant organ systems.

A Novel Complete Autosomal-Recessive STAT1 LOF Variant Causes Immunodeficiency with Hemophagocytic Lymphohistiocytosis-Like Hyperinflammation.

BACKGROUND: Complete signal transducer and activator of transcription 1 (STAT1) deficiency causes a rare primary immunodeficiency that is characterized by defective IFN-dependent gene expression leading to life-threatening viral and mycobacterial infections early in life. OBJECTIVE: To characterize a novel STAT1 loss-of-function variant leading to pathological infection susceptibility and hyperinflammation. METHODS: Clinical, immunologic, and genetic characterization of a patient with severe infections and hemophagocytic lymphohistiocytosis-like hyperinflammation was investigated. RESULTS: We reported a child of consanguineous parents who presented with multiple severe viral infections that ultimately triggered hemophagocytic lymphohistiocytosis and liver failure. Despite intensified therapy with antivirals and cytomegalovirus-specific donor cells, the child died after hematopoietic stem cell transplantation because of cytomegalovirus reactivation with acute respiratory distress syndrome. Exome sequencing revealed a homozygous STAT1 variant (p.Val339ProfsTer18), leading to loss of STAT1 protein expression. Upon type I and type II IFN stimulation, immune and nonimmune cells showed defective upregulation of IFN-stimulated genes and increased susceptibility to viral infection in vitro. Increased viral infection rates were paralleled by hyperinflammatory ex vivo cytokine responses with increased production of TNF, IL-6, and IL-18. CONCLUSIONS: Complete STAT1 deficiency is a devastating disorder characterized by severe viral infections and ensuing hyperinflammatory responses. Early diagnosis can be made by exome sequencing and variant validation by functional testing of STAT1-dependent programmed cell death 1 ligand 1 surface expression on monocytes. Furthermore, high awareness for hyperinflammatory complications and potential targeted treatment strategies such as IL-18 binding protein could be considered. Hematopoietic stem cell transplantation is the only definitive treatment strategy but remains challenging.