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Biomedical subjects

R Ivker

Publications and source records attributed to R Ivker.

7 recordsLinked to original sources
PubMed1997

Hypophosphatemic vitamin D-resistant rickets, precocious puberty, and the epidermal nevus syndrome.

BACKGROUND: The association of multisystem pathologic conditions and epidermal nevi, known as the epidermal nevus syndrome, includes disorders of bone, central nervous system, eye, kidney, vasculature, body symmetry, and skin. Rarely, vitamin D-resistant rickets has been observed in association with this syndrome. Precocious puberty is another rare finding associated with epidermal nevus syndrome, having been observed in 3 patients. OBSERVATION: A female infant with an extensive epidermal nevus, hypophosphatemia, and precocious puberty is described. Despite medical therapy, the patient's phosphate levels continued to be very low (0.87-0.97 mmol/L), establishing the diagnosis of hypophosphatemic vitamin D-resistant rickets. At 21 months of age, areas of the nevus were excised. Laboratory values obtained shortly after the operation showed a significant, but transient, improvement in the serum phosphate level. After a second excision, maintenance of her serum phosphate level in the range of 1.29 to 1.61 mmol/L was possible. CONCLUSIONS: There is evidence that epidermal nevi produce a potent phosphaturic factor. We hypothesize that limited excision debulked the nevus sufficiently to allow medical management of the hypophosphatemia. Surgical intervention should be considered for patients affected with vitamin D-resistant rickets with epidermal nevi. The cause of the precocious puberty is unknown. It may be hypothesized that the nevus released a factor that induced puberty.

Abnormalities, Multiple↗
PubMed1994

Blue vitiligo.

The progression of vitiligo and postinflammatory hyperpigmentation simultaneously in a patient with AIDS led to the appearance of a blue color on much of the patient's skin. The blue coloration subsequently resolved with follicular repigmentation typical of resolving vitiligo. We believe this is the first reported case of "blue vitiligo."

Adult↗
PubMed1990

Three parallel linkage groups of human acidic keratin genes.

Two regions of human genomic DNA, each containing several keratin genes, were isolated and partially sequenced. The keratin genes are inactive, having suffered deleterious mutations. Both regions contain at least four keratin genes arranged in a head-to-tail orientation including a pseudogene for keratin K#16. Within each segment there are two keratin genes in close linkage with only 1.5 kb of DNA between them. Sequence comparison of the two regions showed 98.9% identity in both the coding and the intronic segments of the pseudogenes. The pseudogenes show 94% identity to their functional counterparts. Southern hybridization analysis showed that the segments are paralogous, not allelic. The regions are products of two independent, recent duplication events. The first occurred approximately 24 million years ago, after the separation of primates from the rhesus/baboon line. The second is specific for the human lineage, having occurred approximately 3.8 million years ago. Analysis of the genomic DNAs of primates showed the presence of only one of the regions in the DNAs of gibbon and gorilla, while rhesus monkey and baboon were missing both copies. We conclude that the human keratin genes are still actively evolving, with new duplications having occurred as recently as after the separation of human and gorilla ancestors.

Amino Acid Sequence↗