Epidermolysis bullosa nevus in a patient with recessive dystrophic epidermolysis bullosa: a case report.

We present a case of a 6-year-old girl with recessive dystrophic epidermolysis bullosa (EB) who presented with a large pigmented lesion clinically concerning for melanoma. After histological examination and fluorescent in situ hybridization analysis, diagnosis of EB nevus was performed. EB nevi are benign melanocytic neoplasms with histological findings similar to recurrent nevi occurring in all types of EB. They often mimic melanoma clinically, dermatoscopically, and histopathologically. The ability to recognize an EB nevus is essential for appropriate management of the patient. Unnecessary surgical excision in patients with already high-risk EB should be avoided. Close monitoring of these lesions is recommended because no cases of transformation to melanoma have been described.

Toxic erythema of chemotherapy following leukemia cutis.

A 56-year-old Caucasian male newly diagnosed with acute myelogenous leukemia (AML) M3 presented with a six-week history of multiple painful erythematous nodules scattered on his trunk and extremities, previously treated as abscesses with incision and drainage plus oral trimethoprim-sulfamethoxazole without improvement. A punch biopsy was performed, and the histopathology and immunostaining profile were compatible with leukemia cutis secondary to AML. Induction chemotherapy for AML with cytarabine, etoposide, and mitoxantrone was initiated. Dermatology was reconsulted two weeks later for evaluation and treatment of a new eruption on both dorsal hands and wrists that began three days after starting induction chemotherapy. On physical exam, there were well-demarcated erythematous patches and plaques with mild induration on the hands, extending onto the distal forearms and sparing the dorsal metacarpalphalangeal joints and ventral wrists. Biopsy findings were consistent with toxic erythema of chemotherapy, likely secondary to cytarabine.

DNA repair mediated by endonuclease-independent LINE-1 retrotransposition.

Long interspersed elements (LINE-1s) are abundant retrotransposons in mammalian genomes that probably retrotranspose by target site-primed reverse transcription (TPRT). During TPRT, the LINE-1 endonuclease cleaves genomic DNA, freeing a 3' hydroxyl that serves as a primer for reverse transcription of LINE-1 RNA by LINE-1 reverse transcriptase. The nascent LINE-1 cDNA joins to genomic DNA, generating LINE-1 structural hallmarks such as frequent 5' truncations, a 3' poly(A)+ tail and variable-length target site duplications (TSDs). Here we describe a pathway for LINE-1 retrotransposition in Chinese hamster ovary (CHO) cells that acts independently of endonuclease but is dependent upon reverse transcriptase. We show that endonuclease-independent LINE-1 retrotransposition occurs at near-wildtype levels in two mutant cell lines that are deficient in nonhomologous end-joining (NHEJ). Analysis of the pre- and post-integration sites revealed that endonuclease-independent retrotransposition results in unusual structures because the LINE-1s integrate at atypical target sequences, are truncated predominantly at their 3' ends and lack TSDs. Moreover, two of nine endonuclease-independent retrotranspositions contained cDNA fragments at their 3' ends that are probably derived from the reverse transcription of endogenous mRNA. Thus, our results suggest that LINE-1s can integrate into DNA lesions, resulting in retrotransposon-mediated DNA repair in mammalian cells.

Penile Livedoid Vasculopathy: First Reported Case.

Livedoid vasculopathy is a thromboocclusive cutaneous vasculopathy manifested by livedoid changes, atrophie blanche, and ulceration. The pathogenesis is speculated to involve increasing coagulation or impaired thrombolysis leading to the occlusion of dermal blood vessels with fibrin thrombi. Livedoid vasculopathy is known to primarily affect the lower extremities. We report the first case of livedoid vasculopathy affecting the penis. A 60-year-old male was evaluated for a split urine stream with associated irritation and peeling of the skin of the glans penis. His penile ulcer continued to enlarge despite steroids and antibiotics. Due to diagnostic uncertainty, a biopsy was performed which revealed hyaline thrombi within the lumens of small vessels within the upper to mid dermis, fibrinoid material in the walls of these blood vessels and within the perivascular stroma with overlying and adjacent epidermal spongiosis, and mild perivascular lymphocytic infiltrate with a few scattered neutrophils most consistent with livedoid vasculitis. He was started on aspirin and pentoxifylline with limited improvement and was later started on apixaban with near-complete resolution in 6 months. Penile livedoid vasculopathy has not been previously reported in the English literature. Early diagnosis and treatment are imperative to limit morbidity.

Nonmalignant cutaneous findings associated with vemurafenib use in patients with metastatic melanoma.

Nonmalignant cutaneous findings associated with the use of vemurafenib have only recently been described in the literature. Patients receiving vemurafenib have exhibited cutaneous reactions including prominent follicular plugging, hand-foot skin reaction, exuberant seborrheic dermatitis-like hyperkeratosis of the face, keratosis pilaris, and diffuse spiny follicular hyperkeratosis. Many of these nonmalignant cutaneous findings are associated with abnormal follicular keratinization thought to be secondary to abnormal signaling of the mitogen-activated protein kinase pathway that occurs with the use of BRAF inhibitors. Whether underlying Ras mutations affect this abnormal signaling as in malignant lesions is still unknown. Different therapeutic options exist for these patients that may result in significant improvement in some of these nonmalignant cutaneous findings. Conservative treatment should focus on topical therapies such as topical retinoids or topical steroids. However, systemic therapies such as concomitant oral retinoids or MEK inhibitors should be considered for more severe or refractory cutaneous findings.

Overexpression of Akt converts radial growth melanoma to vertical growth melanoma.

Melanoma is the cancer with the highest increase in incidence, and transformation of radial growth to vertical growth (i.e., noninvasive to invasive) melanoma is required for invasive disease and metastasis. We have previously shown that p42/p44 MAP kinase is activated in radial growth melanoma, suggesting that further signaling events are required for vertical growth melanoma. The molecular events that accompany this transformation are not well understood. Akt, a signaling molecule downstream of PI3K, was introduced into the radial growth WM35 melanoma in order to test whether Akt overexpression is sufficient to accomplish this transformation. Overexpression of Akt led to upregulation of VEGF, increased production of superoxide ROS, and the switch to a more pronounced glycolytic metabolism. Subcutaneous implantation of WM35 cells overexpressing Akt led to rapidly growing tumors in vivo, while vector control cells did not form tumors. We demonstrated that Akt was associated with malignant transformation of melanoma through at least 2 mechanisms. First, Akt may stabilize cells with extensive mitochondrial DNA mutation, which can generate ROS. Second, Akt can induce expression of the ROS-generating enzyme NOX4. Akt thus serves as a molecular switch that increases angiogenesis and the generation of superoxide, fostering more aggressive tumor behavior. Targeting Akt and ROS may be of therapeutic importance in treatment of advanced melanoma.

Allelic heterogeneity in LINE-1 retrotransposition activity.

De novo LINE-1 (long interspersed element-1, or L1) retrotransposition events are responsible for approximately 1/1,000 disease-causing mutations in humans. Previously, L1.2 was identified as the likely progenitor of a mutagenic insertion in the factor VIII gene in a patient with hemophilia A. It subsequently was shown to be one of a small number of active L1s in the human genome. Here, we demonstrate that L1.2 is present at an intermediate insertion allele frequency in worldwide human populations and that common alleles (L1.2A and L1.2B) exhibit an approximately 16-fold difference in their ability to retrotranspose in cultured human HeLa cells. Chimera analysis revealed that two amino acid substitutions (S1259L and I1220M) downstream of the conserved cysteine-rich motif in L1 open reading frame 2 are largely responsible for the observed reduction in L1.2A retrotransposition efficiency. Thus, common L1 alleles can vary widely in their retrotransposition potential. We propose that such allelic heterogeneity can influence the potential L1 mutational load present in an individual genome.

Following the LINEs: an analysis of primate genomic variation at human-specific LINE-1 insertion sites.

The L1 Ta subfamily of long interspersed elements (LINEs) consists exclusively of human-specific L1 elements. Polymerase chain reaction-based screening in nonhuman primate genomes of the orthologous sites for 249 human L1 Ta elements resulted in the recovery of various types of sequence variants for approximately 12% of these loci. Sequence analysis was employed to capture the nature of the observed variation and to determine the levels of gene conversion and insertion site homoplasy associated with LINE elements. Half of the orthologous loci differed from the predicted sizes due to localized sequence variants that occurred as a result of common mutational processes in ancestral sequences, often including regions containing simple sequence repeats. Additional sequence variation included genomic deletions that occurred upon L1 insertion, as well as successive mobile element insertions that accumulated within a single locus over evolutionary time. Parallel independent mobile element insertions at orthologous loci in distinct species may introduce homoplasy into retroelement-based phylogenetic and population genetic data. We estimate the overall frequency of parallel independent insertion events at L1 insertion sites in seven different primate species to be very low (0.52%). In addition, no cases of insertion site homoplasy involved the integration of a second L1 element at any of the loci, but rather largely involved secondary insertions of Alu elements. No independent mobile element insertion events were found at orthologous loci in the human and chimpanzee genomes. Therefore, L1 insertion polymorphisms appear to be essentially homoplasy free characters well suited for the study of population genetics and phylogenetic relationships within closely related species.

A comprehensive analysis of recently integrated human Ta L1 elements.

The Ta (transcribed, subset a) subfamily of L1 LINEs (long interspersed elements) is characterized by a 3-bp ACA sequence in the 3' untranslated region and contains approximately 520 members in the human genome. Here, we have extracted 468 Ta L1Hs (L1 human specific) elements from the draft human genomic sequence and screened individual elements using polymerase-chain-reaction (PCR) assays to determine their phylogenetic origin and levels of human genomic diversity. One hundred twenty-four of the elements amenable to complete sequence analysis were full length ( approximately 6 kb) and have apparently escaped any 5' truncation. Forty-four of these full-length elements have two intact open reading frames and may be capable of retrotransposition. Sequence analysis of the Ta L1 elements showed a low level of nucleotide divergence with an estimated age of 1.99 million years, suggesting that expansion of the L1 Ta subfamily occurred after the divergence of humans and African apes. A total of 262 Ta L1 elements were screened with PCR-based assays to determine their phylogenetic origin and the level of human genomic variation associated with each element. All of the Ta L1 elements analyzed by PCR were absent from the orthologous positions in nonhuman primate genomes, except for a single element (L1HS72) that was also present in the common (Pan troglodytes) and pygmy (P. paniscus) chimpanzee genomes. Sequence analysis revealed that this single exception is the product of a gene conversion event involving an older preexisting L1 element. One hundred fifteen (45%) of the Ta L1 elements were polymorphic with respect to insertion presence or absence and will serve as identical-by-descent markers for the study of human evolution.