Muir-Torre syndrome caused by exonic deletion of MLH1 due to homologous recombination.

BACKGROUND: Muir-Torre syndrome (MTS) is characterized by sebaceous neoplasms with internal malignancies and regarded as a variant of hereditary nonpolyposis colorectal cancer (HNPCC). Pathogenic variations of MTS have been identified in the MSH2, MLH1, and MSH6 genes, with the majority of variations located in MSH2. OBJECTIVES: To present an MTS patient who was the only individual with skin malignancies within a cancer-prone pedigree and to show the usefulness of RNA-based genetic analysis in the investigation of MTS. MATERIALS & METHODS: A 77-year-old man who had operated X-ray equipment at his workplace in his twenties was clinically diagnosed with MTS and investigated by RNA-based analysis, multiplex ligation-dependent probe amplification, and genomic DNA sequencing. RESULTS: The patient had suffered from sebaceous tumours, squamous cell carcinomas of the skin, and colon cancer. The patient's family history was remarkable for visceral malignant diseases. Genetic analysis revealed homologous recombination between two Alu elements within intron 4 and 5 of the MLH1 gene. The rearrangement caused a 1,222-bp deletion, including the entire exon 5. Deletion of exon 5 has previously been reported only in two patients with HNPCC, and not in patients with MTS. CONCLUSION: For the genetic analysis of MTS, the possibility of rare copy number variations of MLH1, as well as MSH2 variations, should be considered. RNA-based screening using puromycin is recommended in order to identify such variations. It remains unclear why only the proband among the pedigree had skin malignancies, however, the skin carcinogenesis might have been related to occupational radiation exposure.

Histological Classification and Differential Diagnosis of Nonepisodic Angioedema With Eosinophilia: A Clinicopathologic Study of 12 Cases With Literature Review.

Nonepisodic angioedema with eosinophilia (NEAE) is a rare condition characterized with monoepisodic angioedema, a nonfebrile state, eosinophilia, normal serum IgM levels, and lack of internal organ involvement. The histology of this disease is not yet well known. The purpose of this study was to characterize the histopathologic features of NEAE. Twelve cases of clinically confirmed NEAE were retrieved from 6 institutions, and these cases were reviewed regarding the clinical data and histopathology, particularly regarding granulomatous lesions. The authors demonstrated that the histology of NEAE can be classified into 3 patterns that of eosinophilic granulomatous panniculitis (7/12 cases), eosinophilic dermatitis without granuloma formation (3/12 cases), and invisible dermatosis (2/12 cases). Six of the 7 granulomatous cases showed the characteristic eosinophilic granulomatous lesions containing individual necrotic adipocytes with membranous fat changes, which could be a differential clue to the diagnosis of NEAE. Review of the previously reported cases (n = 37) revealed that the histological classification could be adaptable to these reported cases. The authors should recognize the histological variation of NEAE and distinguish it from the histological mimickers, including eosinophilic granulomatosis with polyangiitis, erythema nodosum, hypereosinophilic syndrome, and episodic angioedema with eosinophilia.