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.

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.

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.

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.