Germline deletions of EXO1 do not cause colorectal tumors and lesions which are null for EXO1 do not have microsatellite instability.

Exonuclease 1 (EXO1) is a candidate gene for colorectal tumor susceptibility because it is believed to play a role in mismatch repair. There have been several studies investigating the role of EXO1 in mismatch repair but few investigating its role in causing clinical disease. In one recent study, germline variants of EXO1 were reported to be associated with predisposition to colorectal cancer in families with phenotypes similar to hereditary nonpolyposis colon cancer (HNPCC). We recently identified nine individuals from two British families with multiple cutaneous and uterine leiomyomatosis with independently arising heterozygous germline deletions of 1q42.3 approximately q43 encompassing not only FH, the multiple leiomyomatosis-associated gene, but also several flanking genes, including EXO1. We investigated these families for any indication of predisposition to colorectal cancer or other HNPCC spectrum cancers by means of detailed questionnaires, interviews, and examination of EXO1-null skin leiomyomata for microsatellite instability (MSI). No individual in these families had developed colorectal cancer or known colorectal adenomas, and none had any symptoms warranting gastrointestinal or other investigation. EXO1-null tumors showed no evidence of MSI. This study questions the functional significance of previously reported variants of EXO1 reported in HNPCC-like families and suggests that in humans there may be other as yet undiscovered proteins that have exonuclease function overlapping with that of EXO1 in DNA mismatch repair. Also of interest is the absence of phenotypic abnormality apart from multiple leiomyomatosis in any deletion carrier even though the adjacent genes RGS7, KMO, CHML, and OPN3 were also deleted.

Genetic and functional analyses of FH mutations in multiple cutaneous and uterine leiomyomatosis, hereditary leiomyomatosis and renal cancer, and fumarate hydratase deficiency.

Germline mutations of the fumarate hydratase (FH, fumarase) gene are found in the recessive FH deficiency syndrome and in dominantly inherited susceptibility to multiple cutaneous and uterine leiomyomatosis (MCUL). We have previously reported a number of germline FH mutations from MCUL patients. In this study, we report additional FH mutations in MCUL and FH deficiency patients. Mutations can readily be found in about 75% of MCUL cases and most cases of FH deficiency. Some of the more common FH mutations are probably derived from founding individuals. Protein-truncating FH mutations are functionally null alleles. Disease-associated missense FH changes map to highly conserved residues, mostly in or around the enzyme's active site or activation site; we predict that these mutations severely compromise enzyme function. The mutation spectra in FH deficiency and MCUL are similar, although in the latter mutations tend to occur earlier in the gene and, perhaps, are more likely to result in a truncated or absent protein. We have found that not all mutation-carrier parents of FH deficiency children have a strong predisposition to leiomyomata. We have confirmed that renal carcinoma is sometimes part of MCUL, as part of the variant hereditary leiomyomatosis and renal cancer (HLRCC) syndrome, and have shown that these cancers may have either type II papillary or collecting duct morphology. We have found no association between the type or site of FH mutation and any aspect of the MCUL phenotype. Biochemical assay for reduced FH functional activity in the germline of MCUL patients can indicate carriers of FH mutations with high sensitivity and specificity, and can detect reduced FH activity in some patients without detectable FH mutations. We conclude that MCUL is probably a genetically homogeneous tumour predisposition syndrome, primarily resulting from absent or severely reduced fumarase activity, with currently unknown functional consequences for the smooth muscle or kidney cell.

Extracorporeal photopheresis (ECP) in the treatment of chronic graft-versus-host disease (GVHD)

The aim of our study was to assess the efficacy of extracorporeal photopheresis (ECP) in chronic graft-versus-host disease (GVHD). Eleven patients with chronic cutaneous GVHD were studied. Four had mucosal involvement and five had pulmonary involvement. All had failed to improve on first- and second-line therapy. Three patients received ECP alone; the remainder continued to receive steroids and/or immunosuppressive therapy. Patients received ECP twice monthly for 4 months and then once monthly for 3 months. They were evaluated by serial skin scores, mucosal and skin photography, pulmonary function tests, biochemical and haematological parameters. Nine patients showed objective evidence of cutaneous improvement with a mean reduction in skin score of 48% overall. In the 10th patient, skin scores and oral involvement improved on twice monthly ECP but deteriorated when reduced to once monthly. The final patient died from renal failure secondary to cyclosporin toxicity. Two out of five patients with lung involvement showed a mild improvement in pulmonary function tests. Liver function tests were abnormal in five patients; they improved in one and deteriorated in three. All patients receiving concomitant immunosuppressive/steroid therapy were able to reduce drug dosages by trial completion. Our results indicate that ECP can benefit patients with cutaneous and mucosal chronic GVHD who have failed on first- and second-line therapies. The effect on the systemic manifestations of GVHD is less consistent.

B-cell lymphoma associated with chronic lymphatic leukaemia: two cases with contrasting aggressive and indolent behaviour.

The term Richter's syndrome is used to describe the transformation of chronic lymphatic leukaemia (CLL) into a high-grade systemic lymphoma and is associated with a poor prognosis. We have undertaken detailed molecular studies in two patients with cutaneous B-cell lymphoma (CBCL) and CLL. Patient 1 exhibited a low-grade CBCL with different immunoglobulin gene rearrangements in blood and skin. By contrast, patient 2 showed identical gene rearrangements, confirmed by gene sequencing, and died within 4 months of presentation. The latter patient fulfilled the criteria for a diagnosis of cutaneous Richter's syndrome, whereas the former patient demonstrated the coincidence of CLL with a primary CBCL. Our results highlight the importance of gene rearrangement studies with sequencing for the accurate diagnosis of cutaneous Richter's syndrome.

The inherited palmoplantar keratodermas.

The inherited palmoplantar keratodermas (PPK) constitute a complex heterogeneous group of genodermatoses, which are difficult to classify clinically. The application of modern molecular biology techniques are leading to an increased understanding of the genetic bases of these disorders and are paving the way towards a classification based upon molecular pathology. We review the recent research advances in this field and the implications for development of novel approaches to disease management.

Missense mutations in keratin 17 cause either pachyonychia congenita type 2 or a phenotype resembling steatocystoma multiplex.

Pachyonychia congenita (PC) is a group of autosomal dominant ectodermal dysplasias in which the main phenotypic characteristic is hypertrophic nail dystrophy. In the Jackson-Lawler form (PC-2), pachyonychia is accompanied by multiple pilosebaceous cysts, natal teeth, and hair abnormalities. By direct sequencing of genomic PCR products, we report heterozygous K17 missense mutations in the same conserved protein motif in a further five PC-2 families (K17 N92S in one familial and three sporadic cases; K17 Y98D in one familial case) confirming that mutations in this gene are a common cause of PC-2. We also show heterozygous missense mutations in K17 (N92H and R94H) in two families diagnosed as steatocystoma multiplex. Mild nail defects were observed in some but not all of these patients on clinical re-evaluation of these families. All the K17 mutations reported here were shown to co-segregate with the disease in the pedigrees analyzed and were excluded from 100 unaffected, unrelated chromosomes by restriction enzyme analysis of K17 genomic PCR products. We conclude that phenotypic variation is observed with K17 mutations, as is the case with other keratin disorders.

Novel mutations in keratin 16 gene underly focal non-epidermolytic palmoplantar keratoderma (NEPPK) in two families.

Keratins K6 and K16 are expressed in suprabasal interfollicular epidermis in wound healing and other pathological conditions associated with hyperproliferation, such as psoriasis and are induced when keratinocytes are cultured in vitro. However, these keratins are also constitutively expressed in normal suprabasal mucosal and palmoplantar keratinocytes. Mutations in keratins have been reported in the basal keratin pair K5 and K14 in epidermolysis bullosa simplex and in suprabasal epidermal keratins K1, K2 and K10 in epidermolytic ichthyoses. Two families with autosomal dominant disorder of focal non epidermolytic palmoplantar keratoderma, have oral mucosal and follicular lesions in addition to the palmoplantar hyperkeratosis. Previous studies have shown linkage in these families to the type I keratin gene cluster at 17q12-q21 and this report shows that the cDNA of affected members of both families have novel heterozygous mutations in the expressed keratin 16 gene. These mutations (R10C and N8S) lie in the helix initiation motif of the 1A domain. These mutations do not appear to cause epidermolysis on light or electron microscopy, which may reflect differences in function, assembly or interaction of the 'hyperproliferative' or 'mucoregenerative' keratins from other major types of keratins. The mutations reported here are the first to describe the molecular pathology of focal non epidermolytic palmoplantar keratoderma.

O'Brien's actinic granuloma: response to isotretinoin.

We describe a 75-year-old man demonstrating the florid clinical features of actinic granuloma of O'Brien. This rare disfiguring condition is believed to result from a granulomatous reaction of the dermis to solar-induced elastosis and is poorly responsive to topical steroids. Twelve weeks' treatment with isotretinoin prevented the development of new granulomata and produced almost complete resolution of established lesions.

Genetic linkage studies in non-epidermolytic palmoplantar keratoderma: evidence for heterogeneity.

The palmoplantar keratodermas (PPK) are a group of skin diseases characterized by thickening of the skin of the palms and soles due to abnormal keratinization. We have performed linkage analysis on families affected with three distinct forms of non-epidermolytic PPK (NEPPK): focal, diffuse and punctate. Genetic heterogeneity was demonstrated, with focal NEPPK linked to the region on chromosome 17 harbouring the type I keratin cluster, diffuse NEPPK linked to the region on chromosome 12 containing the type II keratin cluster, and in the punctate NEPPK pedigrees, linkage was excluded to both of these keratin clusters. This study provides evidence for genetic differences between these forms of NEPPK and also between NEPPK and epidermolytic PPK (EPPK) in which mutations in keratin 9 have been demonstrated.

Ultrastructural changes resulting from keratin-9 gene mutations in two families with epidermolytic palmoplantar keratoderma.

Palmoplantar keratoderma of Voerner type (or epidermolytic palmoplantar keratoderma) is an autosomal dominant inherited disorder of keratinization with histologic features of epidermolytic hyperkeratosis. We studied members of two large unrelated kindreds with epidermolytic palmoplantar keratoderma, and biopsy specimens of lesional palmar skin from both families confirmed the histologic changes of epidermolytic hyperkeratosis. Whorls of abnormally aggregated keratin filaments were seen ultrastructurally to be associated with signs of cellular disintegration in spinous and granular cells. Direct sequencing of genomic DNA samples obtained from several members of each family established the substitution of a highly conserved arginine by tryptophan (R162W) in the 1A region of the alpha-helical rod domain of keratin 9. This arginine residue in a highly conserved region of keratins 1 and 10 is affected by disruptive missense point mutations in many patients with bullous ichthyosiform erythroderma. An equivalent position in the sole and palm restricted keratin 9 appears to be the mutation hot spot in epidermolytic palmoplantar keratoderma. To date, R162W is the most prevalent genetic defect reported in this genodermatosis.

Auricular embryonal rhabdomyosarcoma.

Rhabdomyosarcoma is an uncommon tumour that may present at a wide variety of different sites. We report a 4-year-old girl who developed an embryonal rhabdomyosarcoma arising in the left pinna which was clinically indistinguishable from a lymphangioma. The case illustrates that this neoplasm can be easily misdiagnosed because of its variable morphology. Early recognition is important as successful treatment is now possible with a combination of chemotherapy, surgery and/or radiotherapy.