Robert Fritsche-Polanz

Mutation analysis of C-KIT in patients with myelodysplastic syndromes without mastocytosis and cases of systemic mastocytosis

The proto‐oncogene C‐KIT encodes a tyrosine kinase receptor that is expressed on mast cells and haematopoietic stem cells and can show somatic mutations in patients with mastocytosis. Only scattered information is available about mutations in C‐KIT in patients with other myeloid neoplasms. Moreover, the prevalence of mutations in C‐KIT in bone marrow specimens of individuals with systemic mastocytosis is largely unknown. Using sequence analysis, we have screened cDNAs of the C‐KIT domain encompassing codon 510–626 and codon 763–858 in bone marrow (BM) mononuclear cells (MNCs) of patients with myelodysplastic syndromes (n = 28) and patients with systemic mastocytosis (n = 12) for the presence of mutations. Furthermore, restriction fragment length polymorphism analysis was applied for identification of the C‐KIT 2468A→T and the C‐KIT 1700T→G mutation, as well as the C‐KIT 1642A→C polymorphism. All 11 patients with systemic indolent mastocytosis tested positive for C‐KIT 2468A→T. In contrast, no mutation was identified in the case of aggressive mastocytosis. Among patients with myelodysplastic syndromes, no patient showed a somatic mutation in C‐KIT. The allele frequency for C‐KIT 1642A→C among the entire patient population was 0·038 and was 0·125 among age‐ and sex‐matched healthy controls. Our data demonstrate that myelodysplastic syndromes without histological or cytological evidence of mastocytosis do not exhibit somatic mutations in exons 10, 11, 12, 16, 17 and 18 of C‐KIT. In contrast, BM MNCs of patients with systemic indolent mastocytosis were all positive for C‐KIT 2468A→T and negative for additional mutations in these exons. The C‐KIT 1642A→C polymorphism is not associated with myelodysplastic syndrome or systemic mastocytosis.

A case of smouldering mastocytosis with peripheral blood eosinophilia and lymphadenopathy

Systemic mastocytosis (SM) is a clonal hematologic disease showing abnormal growth and accumulation of mast cells (MC) in visceral organs with or without skin involvement. The clinical course in SM is variable. In fact, indolent and aggressive variants have been described. In addition, SM patients may acquire an associated hematologic clonal non-MC lineage disease (AHNMD). In some cases, hematologic parameters are indicative of slowly progressing SM although the clinical course remains indolent over years. These cases have been referred to as smouldering SM. We report on a smouldering patient presenting with typical skin lesions, hypercellular marrow with focal MC aggregates, persistent leukocytosis (20,000-30,000/microl) with eosinophilia (5-10%), marked lymphadenopathy, and splenomegaly. The C-KIT mutation Asp-816-Val confirmed the diagnosis of SM. The clinical picture remained stable during an observation period of 10 years without signs of progression to an AHNMD or a high grade MC disease. These data show that some patients with SM can remain in a clinically indolent smouldering state over years even when presenting with marked eosinophilia and lymphadenopathy.

Stem Cell Factor-induced Bone Marrow Mast Cell Hyperplasia Mimicking Systemic Mastocytosis (SM): Histopathologic and Morphologic Evaluation with Special Reference to Recently Established SM-criteria

Although systemic mastocytosis (SM) is a well-defined hematologic neoplasm, it is sometimes difficult to discriminate between SM and a reactive mast cell (MC) hyperplasia. We describe a patient with aplastic anemia who was treated with recombinant stem cell factor (SCF). In response to SCF, the patient showed transient hematologic improvement and developed a marked increase in MC as well as a transient increase in serum tryptase. Histologic and immunohistochemical examination revealed a huge increase in MC in the bone marrow with focal infiltrates similar to SM. However, most of the SM-criteria were not met: First, MC showed normal cytomorphological characteristics without significant atypias (no cytoplasmic extensions, no oval nuclei, no hypogranulated cytoplasm). Furthermore, bone marrow MC were CD2- and CD25-negative and did not exhibit the C-KIT 2468 A → T mutation (Asp-816-Val). After discontinuation of SCF the MC hyperplasia resolved confirming its reactive nature. Based on our case and similar cases mimicking mastocytosis, it seems of importance to apply recently established SM criteria in order to discriminate between reactive MC hyperplasia and true mastocytosis with certainty.

Molecular Analysis of the Carboxy Terminus of the Beta and Gamma Subunits of the Epithelial Sodium Channel in Patients with End-Stage Renal Disease

Background: Mutations in the carboxy termini of the beta subunit (hβENaC) and the gamma subunit (hγENaC) of the human epithelial sodium channel have been identified in patients with Liddle syndrome. Moreover polymorphisms have been described in these genes, the clinical relevance of which for progression to end-stage renal disease (ESRD) is unknown. We, therefore, have screened ESRD patients for putative variants of these genes. Methods: We investigated 256 chronic hemodialysis patients, including 123 patients with a history of hypertension as a cause of ESRD. Screening for mutations in the carboxy termini of hβENaC and hγENaC was accomplished by polymerase chain reaction amplification followed by single-strand conformation polymorphism analysis. Results: In 231 patients single-strand conformation polymorphism analysis of the polymerase chain reaction fragments of the hβENaC and hγENaC genes showed a similar migration pattern as compared with negative control subjects. In 25 patients a band shift was observed. However, sequence analysis in all these patients revealed wild-type sequence. Conclusions: The present study demonstrates the absence of genetic variants in the carboxy terminus of the hβENaC and hγENaC genes in Austrian patients with ESRD maintained on chronic hemodialysis treatment. Thus, mutations in these genes are unlikely to be associated with ESRD.

Numbers of colony-forming progenitors in patients with systemic mastocytosis: potential diagnostic implications and comparison with myeloproliferative disorders.

Background An increase in colony‐forming progenitor cells (CFU) is typically seen in myeloproliferative disorders (MPD). Systemic mastocytosis (SM) is a haemopoietic neoplasm involving myeloid progenitors similar to MPD. In the present study, we measured the levels of peripheral blood (pb) and bone marrow (bm) CFU in patients with different categories of SM, and compared them with those obtained in MPD patients and healthy controls.

Granulocyte function in patients with L-ferritin iron-responsive element (IRE) 39C-->T-positive hereditary hyperferritinaemia-cataract syndrome.

Background  Hereditary hyperferritinaemia–cataract syndrome (HHCS) is an autosomal dominant trait associated with mutations in the iron responsive element (IRE) of the ferritin light‐chain (L‐ferritin) gene. Patients typically show elevated serum ferritin concentrations without iron overload and a bilateral cataract. Hyperferritinaemia can be associated with granulocyte dysfunction in patients with thalassemia beta and in haemodialysis patients. The effect of increased L‐ferritin levels on granulocyte function in patients with HHCS is unknown.