Pathogenesis of pulmonary fibrosis: platelet-derived growth factor precedes structural alterations in the Hermansky-Pudlak syndrome.

Peptides that modulate mesenchymal cell function have been detected in the fibrotic lung disorders once physiologic dysfunction is present. Despite this close association with manifest disease, their role in initiating alveolar remodeling remains unknown. We examined the hypothesis that one potent peptide, platelet-derived growth factor (PDGF), would be present at the alveolar surface before the onset of physiologic dysfunction in patients in whom pulmonary fibrosis subsequently develops. Bronchoalveolar lavage and physiologic assessment were performed in asymptomatic patients with the Hermansky-Pudlak syndrome (n = 30), obligate heterozygous (n = 9), and normal volunteers (control group). Lavage cell number and profile were normal, but alveolar macrophages demonstrated characteristic autofluorescence and ultrastructural features of ceroid. Lavage fluid from physiologically normal patients with Hermansky-Pudlak syndrome and from those with occult restrictive disease demonstrated two PDGF-related peptides (14 kd and 38 kd). Radioligand binding and fibroblast proliferation assay demonstrated that the peptides were functional. By immunoassay the concentration of PDGF in lavage fluid was six times greater than control values (p < 0.01). In situ hybridization together with bioassay indicated that alveolar macrophages were one cellular source of PDGF. Similar results were obtained for heterozygotes. These data identify macrophage-derived PDGF peptides as important candidate molecules in the initiation of alveolar remodeling in the fibrotic lung disorders.

Synergistic effect of storage pool deficient platelets and low plasma von Willebrand factor on the severity of the hemorrhagic diathesis in Hermansky-Pudlak syndrome.

A study of 565 Puerto Rican patients with storage pool deficient (SPD) Hermansky-Pudlak syndrome (HPS) demonstrated that most HPS patients had minor bleeding episodes while others had repeated, severe hemorrhagic episodes requiring transfusion. The severity of bleeding in these latter patients could not be attributed to their SPD alone. As swine with SPD platelets and low von Willebrand factor antigen (vWF:Ag) have more severe hemorrhages than pigs with either defect alone, 146 albino patients and 46 normally pigmented patients were examined for their level of vWF:Ag. The risk of SPD HPS patients having severe, repeated bleeding episodes increased when vWF:Ag fell below 70 U/dL. Family studies indicated that low vWF:Ag levels were more frequently associated with O blood group than from a gene suppressing production or release of vWF1. HPS patients should be tested for vWF:Ag levels.

Molecular analyses of a tyrosinase-negative albino family.

Sequence analysis of the tyrosinase coding region from an individual with tyrosinase-negative oculocutaneous albinism revealed that the patient was a compound heterozygote. One allele carried a C--> A single-base substitution in codon 355 of exon 3, and the other carried a two-nucleotide deletion in exon 1. The nucleotide substitution caused a putative amino acid change from threonine (ACA) to lysine (AAA), abolishing a signal for N-glycosylation. The two base-pair deletion caused a frameshift, creating a putative premature termination signal at codon 226. The melanocytes from the proband and her affected brother were amelanotic and devoid of measurable tyrosinase activity. Moreover, gel electrophoretic analysis of the immunoprecipitated proband tyrosinase showed that the protein was not processed to the mature glycosylated form, confirming the predicted consequence of the amino acid change. The two-base deletion on the homologous allele was detected only by sequencing genomic DNA. The transcript of this allele was not represented in the cDNA library and could not be detected by PCR mRNA, and the putative truncated protein (approximately 25 kDa) was not present in immunoprecipitates, suggesting that the allele with the missense mutation may be preferentially expressed.

Hermansky-Pudlak syndrome in a Swiss population.

Tyrosinase-positive albinism, previously diagnosed as Hermansky-Pudlak Syndrome (HPS), has been examined in four generations from a village of the canton Valais, Switzerland. Homozygotes, obligate heterozygotes and putative heterozygotes in this geneology yielded lower than normal membrane-associated thioredoxin reductase (TR) activities compared with normal family members and controls. All of the homozygotes and 50% of each the obligate and putative heterozygotes showed an increase in bleeding time associated with storage-pool-deficient platelets lacking dense bodies. The TR activity profile and the platelet-dense body deficiency in the Swiss albinos was the same as that in the HPS population from Puerto Rico. However, in albinos from Puerto Rico, there is an accumulation of ceroid/lipofuscin-like pigment in lysosomal structures causing tissue damage, and, upon kidney involvement, this leads to increased urinary dolichol excretion. Approximately half of the Puerto Rican HPS cases had clinical evidence of storage disease with restrictive lung disease, granulomatous colitis, kidney failure and cardiomyopathy. By comparison, the Swiss HPS geneology had a normal life expectancy with no significant evidence for ceroid accumulation or urinary dolichol excretion. An examination of antioxidant enzymes, catalase, TR and glutathione reductase in epidermal suction blisters from Swiss HPS homozygotes showed a similar result for catalase and TR levels to the depigmented epidermis of patients with vitiligo, except that intracellular TR was found to be calcium free in HPS compared with vitiligo. Intracellular glutathione reductase levels were highest in HPS. Both the Swiss and Puerto Rican HPS homozygotes and heterozygotes have giant melanosomes in skin melanocytes.

A frequent tyrosinase gene mutation associated with type I-A (tyrosinase-negative) oculocutaneous albinism in Puerto Rico.

We have determined the mutations in the tyrosinase gene from 12 unrelated Puerto Rican individuals who have type I-A (tyrosinase-negative) oculocutaneous albinism (OCA). All but one individual are of Hispanic descent. Nine individuals were homozygous for a missense mutation (G47D) in exon I at codon 47. Two individuals were heterozygous for the G47D mutation, with one having a missense mutation at codon 373 (T373K) in the homologous allele and the other having an undetermined mutation in the homologous allele. One individual with negroid features was homozygous for a nonsense mutation (W236X). The population migration between Puerto Rico and the Canary Islands is well recognized. Analysis of three individuals with OCA from the Canary Islands showed that one was a compound heterozygote for the G47D mutation and for a novel missense mutation (L216M), one was homozygous for a missense mutation (P81L), and one was heterozygous for the missense mutation P81L. The G47D and P81L missense mutations have been previously described in extended families in the United States. Haplotypes were determined using four polymorphisms linked to the tyrosinase locus. Haplotype analysis showed that the G47D mutation occurred on a single haplotype, consistent with a common founder for all individuals having this mutation. Two different haplotypes were found associated with the P81L mutation, suggesting that this may be either a recurring mutation for the tyrosinase gene or a recombination between haplotypes.

Quantification of a novel dense granule protein (granulophysin) in platelets of patients with dense granule storage pool deficiency.

An antigen-capture sandwich enzyme-linked immunosorbent assay (ELISA) was developed for a novel protein granulophysin, a constituent of the platelet dense granule (DG) membrane and used to characterize patients with dense granule storage pool deficiency (delta-SPD). The assay uses two monoclonal antibodies against the protein, one of which is conjugated to peroxidase. Purified DGs, an enriched source of the protein, were used for the standard curve. Granulophysin levels were only low in forms of delta-SPD associated with albinism. Granulophysin levels in platelet homogenates of 30 patients with the Hermansky-Pudlak syndrome form of delta-SPD were 1/4 to 1/5 of levels in controls or obligate heterozygotes. Two patients with the Chediak-Higashi form of delta-SPD syndrome also had markedly reduced levels of granulophysin. Patients with other forms of delta-SPD had normal levels of granulophysin. Two sisters with delta-SPD in one family had normal granulophysin present in empty dense granule membrane vesicles. Three members of another family with delta-SPD had low DG counts but normal granulophysin levels, indicating that in this group the level of granulophysin was maintained despite the reduction in granule formation. Thus, granulophysin quantitation facilitates characterization of delta-SPD patients and may provide clues to the nature of defective granules in delta-SPD subtypes.

A single base insertion in the putative transmembrane domain of the tyrosinase gene as a cause for tyrosinase-negative oculocutaneous albinism.

We have determined a molecular defect to be the likely basis for inactivity of the tyrosinase (EC 1.14.18.1) from a patient with tyrosinase-negative oculocutaneous albinism. A single base (thymine) was inserted in exon 5 of the tyrosinase gene following codon 471 in the putative transmembrane coding region. This insertion caused a shift in the reading frame of 19 amino acids at the 3' end and introduced a premature termination signal that would be expected to truncate the protein by 21 amino acids at the carboxyl terminus. The albino tyrosinase was not recognized by antibodies directed to the carboxyl terminus of tyrosinase. Furthermore, as shown by gel electrophoresis of the immunoprecipitated protein, the tyrosinase was approximately 3 kDa smaller than normal. Similar immunoprecipitation data were obtained when cloned normal and mutant tyrosinases were expressed in COS-1 cells.

Variable expression of albinism within a single kindred.

We studied the albinotic characteristics in 13 members of a white family (age range, 2 to 73 years), which were graded according to severity and were correlated with visual acuity. Clinical, electrophysiologic, and biochemical characteristics of this family do not fit any known category of human albinism. The degree of heterogeneity in expression of albinotic features was unexpected. The correlation between visual acuity and nystagmus was particularly strong. The brown-haired propositus had severe skin involvement, iris transillumination, fundus hypopigmentation, and foveal hypoplasia. He had no manifest nystagmus, however, and his visual acuity was nearly normal. These observations suggest that nystagmus imposes a visual deficit beyond that related to foveal hypoplasia alone.

Hermansky-Pudlak syndrome (HPS). An epidemiologic study.

A study of albinism in Puerto Rico identified 693 persons with albinism. Among these, the type of albinism was determined in 595, Hermansky-Pudlak syndrome (HPS) was found in 495. Approximately five of every six Puerto Rican albinos had HPS. The highest prevalence of HPS yet reported was in the northwestern quarter of the island where at least 1 in 1,800 persons had HPS, and approximately 1 in 21 were carriers. The HPS albino pigment phenotype was variable, and HPS albinos phenotypically resembled other types of oculocutaneous and ocular albinos. Ceroid storage was also variable. The consistent finding in HPS was storage pool deficient platelets. HPS is best diagnosed by lack of platelet dense bodies seen by electron microscopy. Evidence from family studies indicates that HPS is a distinct disorder due to the pleiotropic effects of a single gene mutation or a small deletion.

Albinism and Hermansky-Pudlak syndrome in Puerto Rico.

Five types of oculocutaneous albinism and two types of ocular albinism were found among 349 Puerto Rican albinos. The most prevalent type of albinism was the Hermansky-Pudlak syndrome (HPS). HPS was observed in five of every six albinos in Puerto Rico. The prevalence of HPS was highest in the northwestern quarter of the island, affecting approximately one in 1,800 persons, and approximately one in 22 are carriers of the gene. HPS is an autosomal recessively inherited triad of a tyrosinase-positive type of albinism, a hemorrhagic diathesis due to storage pool deficient platelets and accumulation of ceroid in tissues. The pigmentary phenotype of HPS albinos resembled that of any other type of oculocutaneous or ocular albinism. The most reliable method of diagnosing HPS is by a deficiency of platelet dense bodies observed by electron microscopy. The accumulation of ceroid in the tissues is associated with fibrotic restrictive lung disease and granulomatous enteropathic disease. The enteropathic disorder resembles Crohn's disease and with few exceptions, had its onset after 13 years of age. The major causes of death were fibrotic restrictive pulmonary disease, hemorrhagic episodes and sequelae of granulomatous enteropathic disease. Menometrorrhagia was common in women with HPS. No immune deficiency was found in HPS patients. The majority of patients with HPS had visual acuities of 20/200 or worse and consequently were legally blind. Albinos of all types, including HPS, lacked binocular vision due to nearly complete crossing of the optic tracts.

Prepubertal diagnosis of Klinefelter syndrome in a patient with taurodontic teeth.

A 9-year, 10-month-old male presented for dental treatment planning for multiple missing permanent teeth. Panoramic radiographs revealed taurodontic permanent first molars and primary second molars. The patient was of slim build with a long lower body and moderately long fingers. Because of the presence of taurodontic teeth, chromosomal analysis was done and revealed 47,XXY - Klinefelter syndrome. Patients with meso- or hypertaurodontic teeth who do not have a syndrome known to be associated with taurodontic teeth should be considered for chromosome analysis because of the high association of taurodontic teeth with X-chromosome aneuploidy syndromes.

Hereditary mucoepithelial dysplasia. Case report and review of the literature.

Hereditary mucoepithelial dysplasia, a dyshesive, dyskeratotic epithelial syndrome caused by an abnormality in desmosomes and gap junctions, involves the mucosae, skin, hair, eyes, and lungs. A 16-year-old patient had nontender, fire-red mucosae; keratosis pilaris; diffuse, nonscarring alopecia; cataracts; photophobia; corneal vascularization; and decreased visual acuity. Histologic examination of gingival sections showed a dyshesive epithelium with atrophy, dyskeratosis, lack of keratinization, and unusual cytoplasmic inclusions. Results of electron microscopic studies showed a reduced number of desmosomes, amorphous intercellular material, and cytoplasmic inclusions resembling tonofilaments and gap junction material. The patient described in this report represents an apparently sporadic case of hereditary mucoepithelial dysplasia. Other cases described previously in the literature are reviewed. We believe this disorder should be brought to the attention of dermatologists because patients with hereditary mucoepithelial dysplasia have numerous skin problems and are susceptible to recurrent infection and potentially fatal bullous lung disease. Also, misinterpreted abnormal results from cervical Pap smears could lead to hysterectomy being performed unnecessarily on these patients.

The role of ceroid in lung and gastrointestinal disease in Hermansky-Pudlak syndrome.

Studies of ceroid associated lesions in Hermansky-Pudlak syndrome (HPS) indicate that restrictive lung disease and granulomatous gastrointestinal lesions are among the most frequent and account for 60% of the deaths of the patients. No defects in the immune system in HPS were found. Histological, ultrastructural and chemical studies show accumulation of non-biodegradable ceroid in tissue cells and associated macrophages of HPS patients. There is no known degradative pathway for ceroid. Ceroid is eliminated from cells by exocytosis. Wild type and pale eared mice treated with leupeptin, which inhibits exocytosis, accumulate ceroid in organ cells in the same sequence seen in HPS. Young HPS patients without significant pulmonary function deficits were lavaged, the macrophages examined by TEM and tested for platelet derived growth factor. Macrophages contained ceroid and 7/12 patients had 27 +/- 42 units of PDGF bioactivity compared to zero activity in controls. Purified ceroid was fed to macrophages lavaged from the lungs of non-smoking control subjects. Prior to feeding, less than 5% of cells contained one or two small yellow-orange autofluorescent granules resembling ceroid. After feeding, approximately 20% of control cells had ingested ceroid, but PDGF was not increased. The immunologic and histologic studies and the production of PDGF by macrophages which precedes lung fibrosis all point to a central role of the macrophage in these lesions. These studies did not distinguish whether the macrophages ingested ceroid from other cells, or whether ceroid is produced intrinsically by the HPS macrophage.

Amelogenesis imperfecta, dentinogenesis imperfecta and dentin dysplasia revisited: problems in classification.

The classification and prevalence of amelogenesis imperfecta is updated based upon new information in the literature. Problems with the currently used classification of inherited dentin defects are discussed.

Hermansky-Pudlak syndrome. Ophthalmic findings.

Prospective ophthalmic evaluation was performed in 20 individuals with Hermansky-Pudlak syndrome, a type of oculocutaneous albinism with an associated deficiency of dense bodies in platelets. The extent of visual impairment and the possible relationship to the degree of hypopigmentation were studied. All patients showed nystagmus, visual acuity ranged from 20/60 to 20/400, and correction of refractive error provided a mild improvement in vision. Iris pigmentation varied in amount and did not correlate with the visual acuity measurement. Foveal hypoplasia was found in all patients, but variability in macular transparency and vascular architecture was noted. Visual-evoked potentials performed in 11 patients demonstrated excessive decussation of optic fibers. Recognition of this form of oculocutaneous albinism is important because of the associated pulmonary, gastrointestinal, renal, and cardiac manifestations of Hermansky-Pudlak syndrome.

Thioredoxin reductase activity in Hermansky-Pudlak syndrome: a method for identification of putative heterozygotes.

Recent studies indicate that membrane-associated thioredoxin reductase (TR) is a possible regulator of melanin biosynthesis via the inhibition of tyrosinase by reduced thioredoxin. In normal individuals, the levels of TR activity in skin correlate linearly to the Fitzpatrick classification of skin type, being lowest in type I skin and highest in skin type VI. In this study, TR was measured in 3-mm skin biopsies in Hermansky-Pudlak syndrome (HPS) patients and their relatives. Forty-five individuals from seven Puerto Rican kindreds were tested, including 12 homozygotes, nine obligate heterozygotes, and 24 unclassified individuals. In addition, seven separate nonkindred HPS patients were tested. With one exception, TR activity was markedly decreased in 18 homozygotes. TR activity was decreased in eight obligate heterozygotes and in 12 unclassified kindred members, whereas 10 subjects had normal TR activity when compared to the expected activity of their skin type. Four individuals were excluded from the analysis because of inadequate controls for their age group or immunosuppressive treatment for kidney transplant. The results indicate that decreased TR activity assayed in 3-mm skin punch biopsies is a useful method for detecting carriers of the HPS gene.

Taurodontism: an anomaly of teeth reflecting disruptive developmental homeostasis.

Two models concerning morphometric traits occurring frequently in aneuploidy states posit, respectively, 1) that they reflect the expression of specific major oligogenes for that trait on the chromosome involved or 2) that they result from a generalized disruption of developmental homeostasis. In contrast to previous studies that have investigated variations in morphometric traits in a single aneuploidy state, this study investigates a single morphometric trait, taurodontism, as it occurs in otherwise normal individuals, in nonchromosomal syndromes, and in aneuploidy syndromes to determine whether the trait best fits the oligogene or the disrupted developmental homeostasis model. Taurodontism is diagnosed from dental radiographs. It is an extreme variation in tooth form seen in multirooted teeth in which the bifurcation or trifurcation of the roots is displaced toward the apex of the root, resulting in increased size of the pulp chamber. The point of furcation, and consequently the size of the pulp chamber, is a quasicontinuously distributed trait. The results indicate that taurodontism most likely is the result of disrupted developmental homeostasis.

Reliability of absent platelet dense bodies as a diagnostic criterion for Hermansky-Pudlak syndrome.

The clinical, pigmentary, and ceroid storage manifestations of the Hermansky-Pudlak syndrome (HPS) triad of albinism, hemorrhagic diathesis, and ceroid storage disease are variable. Therefore, a rapid and accurate method of diagnosing HPS is needed. Platelets of 66 albinos were examined by electron microscopy for the presence or absence of dense bodies. Results show that patients reexamined over a period of 1 year had consistent findings. Those lacking dense bodies (15) when first examined also lacked dense bodies when reexamined a year later, and they had evidence of ceroid storage. Those with dense bodies when first examined (8) also had dense bodies when reexamined, did not have evidence of storage disease, and had types of albinism other than HPS. Of 20 propositi lacking dense bodies, all 32 albino relatives also lacked dense bodies, while 6 albino relatives of 6 propositi with dense bodies also had dense bodies in their platelets. The evidence supports the concept that HPS is a distinct genetic and biochemical disease in which the components of the triad are the result of a single genetic defect, either a point mutation or a small deletion. Comparison of whole mount preparations with thin section preparations of 13 albinos shows that whole mount preparations are an accurate and rapid method for diagnosing HPS. The most consistent diagnostic feature of HPS is lack of platelet dense bodies.