Search

Malignant melanoma is rare in childhood and has never been reported to cause pancytopenia due to bone marrow metastases in a child. We report a 3-year-old boy with a large congenital melanocytic nevus who presented with bone pain and pancytopenia due to diffuse bone and bone marrow infiltration with metastatic melanoma without an identifiable primary site. Despite treatment with imatinib mesylate there was no response and the patient died with progressive disease. This case illustrates an unusual presentation of bone marrow failure secondary to malignant melanoma in a young child with symptomatic metastatic marrow infiltration, a rarely reported site of melanoma involvement in adults or children.

Cowden's syndrome (CS) is an autosomal dominant disorder associated with an increased risk of developing benign and malignant tumors in a variety of tissues, including the skin, thyroid, breast and brain. Women with CS are felt to have an increased risk of developing breast cancer, and virtually all women with CS develop bilateral fibrocystic disease of the breast. Recently, a series of germline mutations have been identified from CS families in a gene known as PTEN/MMAC1/TEP1. In this study, we used heteroduplex analysis and direct sequencing analysis and identified three novel germline mutations in the PTEN/MMAC1/TEP1 coding sequence from unrelated individuals with CS. We report a de novo transition (T-->C) at nucleotide 335 in exon 5. This missense mutation resulted in a leucine to proline (CTA to CCA) change at codon 112. We also describe a novel splice site mutation (801+2T-->G) in intron 7 that caused exon skipping in PTEN/MMAC1/TEP1 mRNA. The third mutation we report is a missense mutation, consisting of a transition (T-->C) at nucleotide 202 in exon 3, resulting in a tyrosine to histidine (TAC to CAC) change at codon 68. Finally, we also detected a rare polymorphism in exon 7 of the PTEN/MMAC1/TEP1 coding sequence. These data confirm the observation that mutations of the PTEN/MMAC1/TEP1 coding sequence are responsible for at least some cases of CS, and further define the spectrum of mutations in this autosomal dominant disorder.

A crucial issue in genetic counseling is the recognition of nonallelic genetic heterogeneity. Hypohidrotic (anhidrotic) ectodermal dysplasia (HED), a genetic disorder characterized by defective development of hair, teeth, and eccrine sweat glands, is usually inherited as an X-linked recessive trait mapped to the X-linked ectodermal dysplasia locus, EDA, at Xq12-q13.1. The existence of an autosomal recessive form of the disorder had been proposed but subsequently had been challenged by the hypothesis that the phenotype of severely affected daughters born to unaffected mothers in these rare families may be due to marked skewing of X inactivation. Five families with possible autosomal recessive HED have been identified, on the basis of the presence of severely affected females and unaffected parents in single sibships and in highly consanguineous families with multiple affected family members. The disorder was excluded from the EDA locus by the lack of its cosegregation with polymorphic markers flanking the EDA locus in three of five families. No mutations of the EDA gene were detected by SSCP analysis in the two families not excluded by haplotype analysis. The appearance of affected males and females in autosomal recessive HED was clinically indistinguishable from that seen in males with X-linked HED. The findings of equally affected males and females in single sibships, as well as the presence of consanguinity, support an autosomal recessive mode of inheritance. The fact that phenotypically identical types of HED can be caused by mutations at both X-linked and autosomal loci is analogous to the situation in the mouse, where indistinguishable phenotypes are produced by mutations at both X-linked (Tabby) and autosomal loci (crinkled and downless).

Structural anomalies of the sex chromosomes provide a means to study the location of genes responsible for sex determination. Recently, a type of sex reversal in humans, the 46,XX male, was shown to result in some cases from translocation of Y chromosome material to the X chromosome. In the present report, another type of sex reversal, the 46,XY female, is shown to result, in two cases, from small deletions of the short arm of the Y chromosome. Prometaphase chromosome analysis showed a 46,X,Yp- karyotype. Several Y chromosome-specific DNA probes were found to be deleted in the two female patients. DNA analysis showed that the two deletions were different but included a common overlapping region likely to be essential for male determination.

Sex-chromosome mosaicism was quantitatively analyzed in two patients using DNA probes specific for human X and Y chromosomes. Both patients were female with stigmata of the Turner syndrome, and both had a 45,X cell line and a 46,XY cell line. One of the patients had a morphologically abnormal, nonfluorescent Y chromosome, dic(Y)(q11). Hybridization of DNA from this patient with two repetitive DNA sequences specific for the heterochromatic region of the Y chromosome indicated that most of the Y-heterochromatic sequences were deleted. DNA from both patients was hybridized with a probe for the DXYS1 locus and found to have the X- and Y-linked loci. Densitometric measurements of the relative intensities of the X- and Y-linked bands were used to calculate the degree of mosaicism in each case. The percentages of 45,X cells obtained by DNA analysis agreed with those obtained by chromosome analysis. DNA analysis provides a way to quantitate mosaicism at the DNA level and in nondividing tissue.