A mutation in the gene for type III procollagen (COL3A1) in a family with aortic aneurysms.

Experiments were carried out to test the hypothesis that familial aortic aneurysms, either thoracic or abdominal, are caused by mutations in the gene for type III procollagen (COL3A1) similar to mutations in the same gene that have been shown to cause rupture of aorta and other disastrous consequences in the rare genetic disorder known as Ehlers-Danlos syndrome type IV. A family was identified through a 37-yr-old female captain in the United States Air Force who was scrutinized only because many of her direct blood relatives had died of ruptured aortic aneurysms. The woman was heterozygous for a single-base mutation that converted the codon for glycine 619 of the alpha 1(III) chain of type III procollagen to a codon for arginine. Studies on cultured skin fibroblasts demonstrated the mutation caused synthesis of type III procollagen that had a decreased temperature for thermal unfolding of the protein. The same mutation was identified in DNA extracted from pathologic specimens from her mother who had died at the age of 34 and a maternal aunt who died at the age of 55 of aortic aneurysms. Examination of DNA from samples of saliva revealed that the woman's daughter, her son, a brother, and an aunt also had the mutation. The results demonstrated that mutations in the type III procollagen gene can cause familial aortic aneurysms and that DNA tests for such mutations can identify individuals at risk for aneurysms.     

A splice junction mutation causes deletion of a 72-base exon from the mRNA for lysosomal acid lipase in a patient with cholesteryl ester storage disease.

The genetic defect leading to cholesteryl ester storage disease (CESD) has been determined in a 12-yr-old patient. Lysosomal acid lipase (LAL) activity in cultured skin fibroblasts was reduced to approximately 9% of control fibroblasts. Plasma cholesterol (255 mg/dl) and LDL-cholesterol (215 mg/dl) were elevated whereas HDL-cholesterol was reduced (19 mg/dl). Triglycerides were moderately elevated (141 mg/dl). There were no clinical abnormalities with the exception of hepatosplenomegaly. Both parents have reduced LAL activity in white blood cells. PCR analysis of the LAL mRNA from the propositus revealed a single slightly smaller mRNA species in skin fibroblasts as well as in leukocytes. The mother of the patient and his older brother had two mRNA species: one of normal size and one of the same size as the propositus. The father has a LAL mRNA of normal size only. Sequence analysis of a PCR-amplified cDNA fragment showed a 72-bp in-frame deletion resulting in the loss of the codons for amino acids 254-277. Analysis of genomic DNA revealed that the 72 bp represent an exon, indicating that the deletion in the mRNA is caused by defective splicing. Sequence analysis of the patient's genomic DNA revealed a G-->A substitution in the last nucleotide of the 72-bp exon in one of his alleles. The mutant allele was shown to cosegregate with the truncated mRNA in the pedigree, providing further evidence that the G-->A substitution causes aberrant splicing and exon skipping. No normal-sized mRNA is detectable in the propositus even though he is not homozygous for the splice site mutation. This can be only accounted for by assuming that he is a compound heterozygote with a null allele inherited from his father. In summary, the data presented provide evidence that deletion of the codons for amino acids 254-277 in the LAL mRNA in combination with a null allele cause the clinical expression of CESD in our patient.     

Studies in porphyria. IV. Expression of the gene defect of acute intermittent porphyria in cultured human skin fibroblasts and amniotic cells: prenatal diagnosis of the porphyric trait

The gene lesion of the porphyrin-heme synthetic pathway in acute intermittent porphyria (AIP) is reflected in a deficient level of activity of the cytosol enzyme uroporphyrinogen I synthetase (URO-S). A marked URO-S deficiency has been demonstrated in the liver and in circulating erythrocytes of individuals with both active and latent AIP. This enzymic abnormality accounts for the excessive production and excretion into urine of the porphyrin precursors, lamda-aminolevulinic acid (ALA) and porphobilinogen (PBG) in AIP subjects. In this study, utilizing cell culture techniques, a marked URO-S deficiency has also been demonstrated in skin fibroblasts from AIP patients and in cells derived through aminocentesis from an approximately 17-wk old fetus. The prenatal diagnosis of the AIP trait in this fetus was confirmed postnatally by the demonstration in the child of a deficient level of erythrocyte URO-S activity which was comparable to those found in her AIP mother and affected sibling and which was approximately one-half the levels characterizing her normal father and aunt and a second unaffected sibling. The identification of the URO-S deficiency in cultured human fibroblasts from AIP patients was facilitated by a newly developed, sensitive assay for the enzyme activity. In this assay, the ability of such cells to convert ALA to protoporphyrin was quantitated; in the sequence of reactions involved in this transformation, URO-S is limiting so that the gene defect of AIP could be simply and precisely determined by appropriate spectrofluorometry of cell extracts. The technique described has distinct advantages over the direct enzymatic assay for URO-S activity in cultured human skin fibroblasts and permits clear differentiation of AIP carrier from normal individuals.     

Emergency department presentation of ‘delusional parasitosis by proxy’. Delusional parent,injured child

We report a case of 'delusional parasitosis by proxy'. A sixyear old child was brought to the emergency department by a mother with concerns that her son had a skin and scalp infestation. Despite the absence of any clinical findings being found on exam, the mother remained disproportionately concerned. Follow up care was recommended with the child's primary care. The mother returned to the ED with her child three weeks later with concerns that her son had an inflamed scalp and eyes. The mother remained insistent that the child was infested with bugs and she had sought care at two other locations where the child was prescribed permethrin on both visits. She had been applying the medication repeatedly. On exam the boy's scalp had been shaved and was erythematous and irritated; his eyebrows and eyelashes had also been shaved off and likely contributed to an irritant conjunctivitis from repeated applications of topical permethrin lotion. No evidence of infestation was identified. We recruited the assistance of the maternal grandparents, child protective services and primary care pediatrics and the child was removed from the mother's custody and placed into the custody of the grandparents. Six weeks later with basic skin care and erythromycin ophthalmic ointment for the eyes, the child's hair, eyebrows and eyelashes grew had grown in, and the scalp irritation had resolved. The mother had sought and received psychiatric care and was improving.     

Identification of a dysfibrinogenemia of gammaR275C (Fibrinogen Fukushima)

BACKGROUND: Various dysfibrinogenemias have been identified worldwide. This paper describes a case of dysfibrinogenemia recently identified in our laboratory. PATIENT: A 34-year-old pregnant woman without any clinical complaints was admitted to our hospital for delivery. She had an extremely low fibrinogen concentration as determined by the thrombin time method though immunoassay showed a titer within the reference range. Dysfibrinogenemia was suspected and further analyses were performed including on her family. Thrombin time was measured using human and bovine thrombin with and without calcium ion. Reptilase time was also measured. To identify the genetic mutation responsible for this dysfibrinogen, genomic DNA extracted from the blood was analyzed for mutation-rich regions in the fibrinogen gene. RESULTS: The subject, her mother and her two infants showed the same pattern of results while her father showed a regular pattern. Thrombin time calculated using both human and bovine thrombin and reptilase time was elongated in the propositus. The extent of the elongation was decreased in the presence of calcium ion. DNA sequencing showed heterogeneous fibrinogen gammaR275C mutations in the propositus, mother and two children. The father showed no mutation. CONCLUSIONS: A case of dysfibrinogenemia gammaR275C without any clinical symptoms was found by routine coagulation testing and was genetically identified.     

Generation of full‐thickness skin equivalents using hair follicle‐derived primary human keratinocytes and fibroblasts

Skin equivalents are increasingly used as human‐based test systems for basic and preclinical research. Most of the established skin equivalents are composed of primary keratinocytes and fibroblasts, isolated either from excised human skin or juvenile foreskin following circumcisions. Although the potential of hair follicle‐derived cells for the generation of skin equivalents has been shown, this approach normally requires microdissections from the scalp for which there is limited subject compliance or ethical approval. In the present study, we report a novel method to isolate and cultivate keratinocytes and fibroblasts from plucked hair follicles that were then used to generate skin equivalents. The procedure is non‐invasive, inflicts little‐pain, and may allow easy access to patient‐derived cells without taking punch biopsies. Overall, minor differences in morphology, ultrastructure, expression of important structural proteins, or barrier function were observed between skin equivalents generated from hair follicle‐derived or interfollicular keratinocytes and fibroblasts. Interestingly, improved basal lamina formation was seen in the hair follicle‐derived skin equivalents. The presented method here allows easy and non‐invasive access to keratinocytes and fibroblasts from plucked hair follicles that may be useful particularly for the generation of skin disease equivalents.     

Mutant feedback-resistant phosphoribosylpyrophosphate synthetase associated with purine overproduction and gout. Phosphoribosylpyrophosphate and purine metabolism in cultured fibroblasts.

We have reported previously two siblings with gout and uric acid lithiasis associated with excessive purine production. In the erythrocytes of these patients, phosphoribosylpyrophosphate (PRPP) synthetase exhibited resistance to feedback-inhibition by normal cell constituents such as guanosine-5'-diphosphate (GDP) and adenosine-5'-diphosphate (ADP), resulting in superactivity of the mutant enzyme and consequently in increased PRPP content and availability for nucleotide synthesis. Erythrocyte PRPP content and availability were normal in the propositus' parents, his healthy brother and three sons, and they all had normal serum level and urinary excretion of uric acid, except for the mother who was hyperuricosuric. To further characterize this mutation we studied PRPP and purine metabolism in cultured fibroblasts of the affected family. PRPP synthetase in dialyzed lysates of fibroblasts from the propositus and his mother exhibited increased specific activity, more markedly at low inorganic phosphate concentration, and decreased sensitivity to inhibition by ADP and GDP, PRPP content and availability and the rate of de novo purine nucleotide synthesis were markedly increased in the fibroblasts of the propositus and to a lesser extent in the fibroblasts of his mother but were normal in the fibroblasts of the other family members investigated. The fibroblast studies demonstrate the following sequence of abnormalities: feedback-resistance of PRPP synthetase; superactivity of this enzyme in normal physiological milieu; increased availability of PRPP; and increased de novo synthesis of purine nucleotides. The pattern of inheritance of this disorder is compatible with both an X-linked recessive and autosomal dominant traits.     

Use of selective media for distinguishing variant forms of hypoxanthine phosphoribosyl transferase

Growth properties of cultured fibroblasts in selective media were used to characterize the HPRT enzyme of a patient with a new variant of hypoxanthine phosphoribosyl transferase (HPRT) with deficient activity. The clinical phenotype of the patient was typical of the Lesch-Nyhan syndrome. However, cells of the patient were not selected for by growth in either 8-azaguanine or 6-thioguanine. Assay of the activity of the enzyme in erythrocyte lysates revealed values of approximately zero, while in the intact fibroblast assay the level of activity was 1.4% of normal. The heterozygous mother of the patient, unlike heterozygotes for the classic Lesch-Nyhan enzyme, had a level of activity in erythrocyte lysates that was 45% of control. In the presence of selective agents in vitro the cells of the patient retained sufficient HPRT activity to permit a degree of toxicity indistinguishable from that observed in normal cells although the degree of the deficiency was so great that it led to the complete Lesch-Nyhan phenotype. These findings call into question the use of selective agents for the identification of HPRT- cells in the detection of heterozygosity.     

Neonatal murine skin‐derived cells transplanted using a mini‐chamber model produce robust and normal hair

Hair follicle reconstitution models are useful tools for investigating signalling and cytokines during hair follicle morphogenesis and cycling. The chamber model is one of the most established methods available for the study of hair follicle reconstitution and appears to be the most reproducible. However, the chamber model has several deficiencies: infection of skin wounds and subsequent animal death commonly occur, a large number of cells are required and only one chamber can be transplanted onto each animal. We modified these deficiencies by using a mini‐chamber method, which has the advantages of having a high graft take rate, requiring fewer cells and allowing several mini‐chambers to be transplanted onto each animal. In our study, cultured dermal cells at different passages (0 to high) lost the ability to reconstruct hair follicles, but dermal cells cultured overnight (12 h) retained this ability. Using the assay, newborn mice dermal cells that were freshly isolated and cultured overnight (12 h), as well as cultured dermal papilla cells from mice vibrissa follicles, all reconstructed hair follicles. However, cultured dermal papilla cells from human scalp follicles could not reconstruct hair follicles. Copyright © 2013 John Wiley & Sons, Ltd.     

Estrogen exposure in a child from hair lotion used by her mother: clinical and hair analysis data

Premature estrogenic effects may result from exogenous exposure to estrogenic substances. We report the case of a 36-month-old girl who presented with vaginal bleeding, uterus enlargement, and thelarche. Questioning of the parents revealed that the child's mother had used hormone-based hair lotions on her own scalp and that the child was in the habit of playing with her mother's hair while falling asleep, and that the girl played with her mother's combs and the empty lotion vials. The onset of hyperestrogenic syndrome was temporally related to the handling of lotions containing ethynylestradiol 0.5%. Analysis of long scalp hairs from the girl and her mother identified ethynylestradiol in concentrations of 10.6 and 46.6 microg/g, respectively. Six months after the mother discontinued use of the estrogen-containing hair lotion, the girl's hyperestrogenic signs resolved. This case highlights the importance of obtaining histories of possible food and non-food environmental sources of contamination, the suitability of hair sampling to identify the origin of the contamination, and the opportunity to warn parents about hazards related not only to oral contraceptives, but also custom-compounded topical hormone preparations.     

Arduous navigation: the life story of a family raising a young child with Prader-Willi syndrome

The purpose of this narrative research was to explore the life experience of a family with a son suffering from congenital Prader-Willi syndrome (PWS). Difficulties associated with raising a PWS child led the mother to leave the family with her afflicted son. The author analyzed the story of this family and applied metaphors to describe the course of the family's life in terms of a "navigational map of life". This map included the six components of: 1. Leaving port (sailing toward an unknown future); 2. Facing a tsunami (undergoing a trial from God); 3. Striking a reef (a fragile boat in a vast ocean); 4. Isolated on an island (the interdependent relationship between mother and child); 5. Transformation (adjustment and starting over); and 6. Hoisting the sails (staying to the course of making dreams come true). In this study, the researcher served as the nu rse case manager and interacted with family members to provide health care, consultation and support as needed. The mother of this young PWS child has empowered herself, overcome her suffering and prepared herself well to face the challenges of the future.     

Detection of germline mosaicism in two Duchenne muscular dystrophy families using polymorphic dinucleotide (CA)n repeat loci within the dystrophin gene.

BACKGROUND: Approximately one-third of new cases of Duchenne muscular dystrophy (DMD) can be attributed to sporadically arising new mutations, however in the majority of cases the DMD mutation has been inherited from the mother. These female carriers can have either a constitutive or mosaic mutation. AIM: The aim of this study was to determine the segregation of the at-risk haplotype and to find a deletion in the dystrophin gene of patients. METHOD: We analyzed individuals from two families with a history of DMD in order to predict the carrier status of related females. In one of these cases the mother had two affected sons, while in the other one son and two grandchildren were affected; therefore we predict that the mother would be an obligatory carrier. RESULTS: Haplotype analysis of the DMD loci revealed that in the two families both the healthy and affected brothers had inherited the same X maternal chromosome. However, the affected brother carried a deletion, which was absent in the unaffected sibling. CONCLUSION: These findings suggested that the mothers in the two families were germline mosaics for the DMD gene. The results of this study demonstrate the usefulness of the methodology that combine the haplotype analysis with the identification of the mutation in order to detect hidden germline mosaicisms and, thus, improve genetic counseling.     

Biochemical characterization of variants of the Ehlers-Danlos syndrome type VI

Three variants of the Ehlers-Danlos syndrome type VI are described: a severe form with skeletal, dermal and ocular manifestations associated with a lack of hydroxylysine in skin and little lysyl hydroxylase activity in cultured fibroblasts; a similarly affected form with a nearly normal hydroxylsine content in skin, but with only little enzyme activity in cultured fibroblasts; and a predominantly ocular form with no biochemical abnormality in skin or cultured skin fibroblasts. The activities of prolyl 4-hydroxylase and the two hydroxylysyl glycosyltransferases were normal in all cases, and the failure to find lysyl hydroxylase activity was not due to altered solubility characteristics of the enzyme or to the presence of an enzyme inhibitor. The collagen produced in cell culture, however, was hydroxylated to a markedly higher extent than that found in skin. In both the mutant and control cells hydroxylation of lysyl residues was less sensitive to ascorbate deficiency than that of prolyl residues.     

HURLER'S SYNDROME : A GENETIC STUDY IN CELL CULTURE

Seven families affected with Hurler's syndrome have been studied using the methods of cell culture. Skin fibroblasts obtained from the skin of 7 patients with Hurler's syndrome contained metachromatic granules when stained for mucopolysaccharides with toluidine blue O and alcian blue, whereas fibroblasts from normal subjects contained no metachromatic granules. In four families skin cultures of the clinically normal parents showed fibroblasts which contained demonstrable metachromatic granules and "gargoyle" cells and were considered to be heterozygous for the abnormal gene. Fibroblast cultures from certain other members of these families showed metachromasia. These findings were also considered to indicate heterozygosity for the abnormal gene. Three families of the X-linked type of the disease were studied. Fibroblasts cultured from the father contained no metachromatic granules whereas those of the hemizygous mother contained both metachromatic granules and "gargoyle" cells. In one family the abnormal gene could be traced through unaffected individuals for three generations. The prolonged preservation of the biochemical trait in tissue culture will permit studies to be performed designed to clarify the primary action of the abnormal genes which result in Hurler's syndrome, as well as to increase the usefulness of this trait in mapping the human X chromosome.     

Enhanced accumulation of hyaluronate in the culture of skin fibroblasts from two patients with Coffin-Lowry syndrome

Cultured skin fibroblasts were prepared from two unrelated adult patients with full expressions of Coffin-Lowry syndrome. Glycosaminoglycans (GAGs) were isolated either from the medium or from the cell layer of cultured skin fibroblasts. Two-dimensional electrophoresis of GAG preparations on cellulose acetate film revealed that hyaluronate was the major component both in the medium and in the cell layer. Quantitative analysis of GAGs was carried out by measuring optical density at 615 nm of Alcian blue-stained GAG spots on electrophoretograms. Increase in the hyaluronate content was found both in the culture medium and in the cell layer of Coffin-Lowry fibroblasts. In addition, the incorporation of [14C]glucosamine into hyaluronate was similarly activated in skin fibroblasts from patients, suggesting the active biosynthesis and or the suppressed degradation of hyaluronate by cultured skin fibroblasts from Coffin-Lowry syndrome. The abnormal metabolism of hyaluronate in Coffin-Lowry fibroblasts may be implicated in some of the clinical aspects of this genetic disorder.     

Induction of hair follicle neogenesis with cultured mouse dermal papilla cells in de novo regenerated skin tissues

De novo skin regeneration with human keratinocytes amplified in culture is a life‐saving procedure for patients with extensive skin loss and chronic wounds. It also provides a valuable platform for gene function and therapeutic assessments. Nevertheless, tissues generated in this manner lack hair follicles that are important for skin homeostasis, barrier function, and repair. In this study, we generated skin tissues with human keratinocytes combined with dermal papilla (DP) cells isolated from mouse whisker hair. For this, cultured keratinocytes and mouse DP (mDP) cells were mixed at 10:1 ratio and seeded onto devitalized human dermal matrix derived from surgically discarded human abdominoplasty skin. After 1 week in submerged culture, the cell/matrix composites were grafted onto the skin wound beds of immunocompromised NSG.SCID mice. Histological analysis of 6‐week‐old skin grafts showed that tissues generated with the addition of mDP cells contained Sox2‐positive dermal condensates and well‐differentiated folliculoid structures that express human keratinocyte markers. These results indicate that cultured mDP cells can induce hair follicle neogenesis in the de novo regenerated skin tissues. Our method offers a new experimental system for mechanistic studies of hair follicle morphogenesis and tissue regeneration and provides insights to solving an important clinical challenge in generation of fully functional skin with a limited source of donor cells.     

Reduced affinity of the androgen receptor for 5 alpha-dihydrotestosterone but not methyltrienolone in a form of partial androgen resistance. Studies on cultured genital skin fibroblasts.

We have studied a child with posterior labial fusion, clitoral phallus, female urethra, and a short, blind vagina born to a mother with decreased axillary and pubic hair. Her karyotype is 46,XY. At 2 yr of age, the child's basal level of plasma testosterone was less than 0.35 nM and after human chorionic gonadotropin stimulation, it rose to 2.6. Testis and epididymis histology were normal. Her cultured genital (labial) skin fibroblasts have normal testosterone 5 alpha-reductase activity, and metabolize 5 alpha-dihydrotestosterone (DHT) normally, but they do not augment (up-regulate) their basal androgen-receptor binding activity during prolonged incubation with DHT. With DHT, the androgen receptor in her genital skin fibroblasts has a normal binding capacity (maximum binding capacity = 25 fmol/mg protein), but an increased rate constant of dissociation (k = 11.6 X 10(-3) min-1; normal, 6 +/- 1.2 (+/- SD)), and a decreased apparent equilibrium binding affinity (Kd = 0.6 nM; normal, 0.22 +/- 0.09) that is evident in the results of 2-h assays but not of those lasting 0.5 h. With the synthetic androgen, methyltrienolone, all three binding properties of the receptor are normal, and her receptor activity up-regulates normally. We interpret these results to mean that the subject has a ligand-selective defect in the time-dependent transformation of initial, low-affinity androgen-receptor complexes to serial states of higher affinity, presumably as the result of a structural mutation at the X-linked locus that encodes the androgen receptor protein.     

Abnormal copper metabolism and deficient lysyl oxidase activity in a heritable connective tissue disorder.

Biochemical abnormalities were studied in two brothers with bladder divericulas, inguinal hernias, slight skin laxity, and hyperelasticity and skeletal abnormalities including occipital exostoses. Lysyl oxidase activity was low in the medium of cultured skin fibroblasts, this abnormality being accompanied by reduced conversion of the newly synthesized collagen into the soluble form. Copper concentrations were markedly elevated in the cultured skin fibroblasts, but decreased in the serum and hair. Serum cerulophasmin levels were also low. The reduced lysyl oxidase activity is suggested to be responsible for ther clinical manifestations, but the deficiency in this copper-dependent enzyme may be secondary to the abnormalities in the metabolism of the cation. Nevertheless, a mutation directly affecting both lysyl oxidase and an intracellular copper transport protein cannot be excluded. The disease is tentatively classified as one subtype of the Ehlers-Danlos syndrome.     

两个遗传性凝血因子Ⅶ缺乏症家系分子缺陷的初步探讨

目的：探讨两个遗传性凝血因子Ⅶ（FⅦ）缺乏症家系的基因突变类型。方法：用DNA直接测序法对2例患者及其家庭成员FⅦ基因进行分析；应用等位基因特异PCR（ASPCR）以及PCR辅助酶切反应鉴定是否有基因改变。结果：家系A中先证者有两种基因突变：6390位T→G导致Trp40Cys,11496位G→A导致Arg353Gln，这两个突变均为杂合子；PCR辅助MspⅠ酶切证实其母亲也是杂合子Arg353Gln。家系B的先证者有11482T→G，导致His348Gln,PCR辅助NspⅠ酶切证实称证者及其女含有同样的杂保子基因突变，不安现有11514位C→T导致Thr359Met,ASPCR证实先证者及其子携带同样的杂合子突变基因。结论：在两个遗传性FⅦ缺乏症家系中找到3种FⅦ基因的错义突变，其中Trp40Cys为首次报道。     

Disparate Enzyme Activity in Erythrocytes and Leukocytes. A VARIANT OF HYPOXANTHINE PHOSPHORIBOSYL-TRANSFERASE DEFICIENCY WITH AN UNSTABLE ENZYME

A family is reported in which each of two sisters has a son with no detectable hypoxanthine phosphoribosyltransferase (HPRT) (EC 2. 4. 2. 8) in his erythrocytes, a finding considered pathognomonic of Lesch-Nyhan disease. However, neither has the stigmata of the disease. One boy is neurologically normal, and the other is moderately retarded. There was only a slight increase in urinary uric acid, but the amounts of hypoxanthine and xanthine, and their ratios, were similar to those found in Lesch-Nyhan disease, strongly indicating that excesses of these last two oxypurines are not responsible for the symptomatology in that disease. In contrast to the nondetectable HPRT activity in the red blood cells, leukocyte lysates from the two boys have 10-15% of normal activity, possibly reflecting continuing synthesis of an unstable enzyme. This hypothesis is supported by the demonstration that at 4 degrees C HPRT activity was rapidly lost in the propositus while the activity increased in control subjects. The mother's cells were intermediate between the two. The intact and disrupted leukocytes of the hemizygote, in the absence of added phosphoribosyl converted as much hypoxanthine to inosinate as the normal cell, and appropriate tests indicated that under these circumstances enzyme concentration is not rate limiting whereas the concentration of the cosubstrate, phosphoribosyl pyrophosphate, is. The capacity for normal function in the intact mutant cell is more representative of in vivo conditions than the lysate, which may explain the important modification of clinical symptomatology, the relatively mild hyperuricosuria, and the presence of mosaicism in the circulating blood cells of the heterozygotes. A similar explanation may apply to other genetic diseases in which incomplete but severe enzyme deficiencies are found in clinically normal individuals.An associated deficiency in glucose-6-phosphate dehydrogenase in this family permitted confirmation of previous observations on linkage with hypoxanthine phosphoribosyltransferase.