Distichiasis-lymphoedema: clinical features, venous function and lymphoscintigraphy.

Distichiasis-lymphoedema is a rare variant of the genetically determined lymphoedemas; distichiasis is the abnormal development of the meibomian glands causing aberrant growth of eyelashes. However, a better understanding of this clinically distinct subgroup may provide useful information on the genetic inheritance of all types of lymphoedema. This report provides phenotype data on a very large family with distichiasis-lymphoedema. Lymphoscintigraphy and light reflection rheography (venous function) were undertaken to identify the phenotype more clearly. As a result of lymphoscintigraphy several subjects were reclassified phenotypically (unaffected or affected) with implications for genetic linkage studies. Associated congenital abnormalities were found and venous abnormalities were almost always present in affected limbs. A dominant inheritance with incomplete penetrance was confirmed.

Characterization of the major susceptibility region for psoriasis at chromosome 6p21.3.

Psoriasis is a common inflammatory skin condition caused by genetic and environmental factors. Recent genome-wide linkage analyses have identified a locus encoding susceptibility to psoriasis and placed this gene in the 12 cM interval between markers D6S426 and D6S276 on chromosome 6p21.3. This is a broad region and encompasses the human major histocompatibility complex. We have sought to localize the susceptibility gene more precisely by exploiting the linkage, haplotype, and linkage disequilibrium information available through genotyping 118 affected sib pairs, their parents and other affected family members. A total of 14 highly polymorphic markers were genotyped, combining anonymous loci with the class I genes HLA-B and -C distributed across a genetic interval of approximately 14 cM including the entire major histocompatibility complex. Through the application of higher density mapping within the major histocompatibility complex, we identified those regions most commonly shared identical by descent in patients with psoriasis. Using the transmission-disequilibrium test, we found significant evidence of linkage and allelic association across an interval defined by the markers tn62 (p = 1.0 x 10(-7)), HLA-B (p = 4.0 x 10(-7)), and HLA-C (p = 2.7 x 10(-9)), a region encompassed within a 285 kb genomic DNA fragment. Hence these studies contribute to the refinement of the localization of a major psoriasis susceptibility gene and place the critical region near to HLA-C.

Lack of c-kit mutation in familial urticaria pigmentosa.

Somatic mutations within c-kit have been reported in individuals with mastocytoses, including urticaria pigmentosa (UP). We have identified three siblings with UP. We aimed to determine whether the c-kit proto-oncogene was playing a part in the aetiology of UP in these three siblings. Using seven microsatellite repeat markers spanning an 8-cM interval encompassing the c-kit gene we followed the transmission of the c-kit gene in this family. Furthermore, single-strand conformation polymorphism analysis was used to scan exon 17 of the c-kit gene for mutations in genomic DNA of all family members and somatic DNA extracted from skin of the eldest affected sibling, the proband. No mutations were found in exon 17 in either genomic DNA of all family members or somatic DNA of the proband. Patients with UP have been shown to possess somatic mutations of the c-kit gene. However, this locus has been excluded as playing a part in the three siblings examined here in whom a second gene locus must be determining their UP. Therefore, this study emphasizes genetic heterogeneity in UP. Future study to identify primary molecular determinants of UP should include affected sib-pair studies.

Painful subcutaneous fat necrosis of the newborn associated with intra-partum use of a calcium channel blocker.

Subcutaneous fat necrosis of the newborn (SCFN) is a relatively uncommon condition of the skin which is said to be benign and painless. We report an infant with extremely painful SCFN which was relieved only by opiate analgesia. SCFN normally resolves spontaneously within a few weeks. This case is, therefore, also unusual in that symptoms persisted beyond 6 months.

Identification of a major susceptibility locus on chromosome 6p and evidence for further disease loci revealed by a two stage genome-wide search in psoriasis.

Psoriasis is a common chronic inflammatory disorder of the skin. To further understand the pathogenesis of psoriasis we have chosen to investigate the molecular genetic basis of the disorder. We have used a two-stage approach to search the human genome for the location of genes conferring susceptibility to psoriasis, using a total of 106 affected sibling pairs identified from 68 independent families. As over a third of the extended kindreds included affected relatives besides siblings, in addition to an analysis of allele sharing between affected sibling pairs, a novel linkage strategy was applied that extracts full non-parametric information. Four principal regions of possible linkage were identified on chromosomes 2, 8, 20 (p <0.005) and markers from the MHC region at 6p21 (p <0.0000006) for which significant evidence of linkage disequilibrium was also observed (p <0.00002). Whilst data from limited case control associations exist to implicate the MHC, the results of this genome wide analysis demonstrate that, at least in the population studied, a gene or genes located within the MHC and close to the class 1 HLA loci, represent the major determinant of the genetic basis of psoriasis.

Urticaria pigmentosa coexisting with multiple myeloma.

We present the case of a 44-year-old white male who developed multiple myeloma complicated by acute renal failure 8 years after the onset of urticaria pigmentosa. Mast cell disease has been associated with a number of haematological malignancies, particularly those from the myeloid lineage. Lymphoproliferative disorders have also been linked with mast cell disease but an association with multiple myeloma has not previously been described. Patients with urticaria pigmentosa should undergo simple screening blood tests to exclude an underlying haematological malignancy.

Imported mucocutaneous leishmaniasis.

We report a case of mucocutaneous leishmaniasis in a otherwise fit Caucasian man who had traveled in an endemic area. Initial tissue microscopy failed to identify the causative organism, which was only determined by subsequent culture as Leishmania braziliensis. This case illustrates the variability in the presence of Leishman-Donovan (LD) bodies in histopathological studies and emphasizes the need for culture in suspected cases of leishmaniasis, particularly given the ability of certain Leishmania species such as L. braziliensis to cause recalcitrant and destructive infections of the nose and mouth.

An association between psoriasis and hereditary multiple exostoses. A clue for the mapping of a psoriasis susceptibility gene?

Chronic plaque psoriasis affects approximately 1.6% of the U.K. population. Population, family and twin studies all strongly suggest an important genetic component in the pathogenesis of the disease, although genetic linkage studies have, so far, failed to identify susceptibility genes. We describe a family in which psoriasis cosegregates through three generations with a known autosomal dominant disorder, hereditary multiple exostoses (HME). A major locus for HME has recently been mapped to chromosome 8q. Observations in this family may provide a mapping clue for a psoriasis susceptibility gene.