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Heritable Illnesses of the Navajo: Fallout of the American Indian Wars of the 19th Century.

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Presentation on theme: "Heritable Illnesses of the Navajo: Fallout of the American Indian Wars of the 19th Century."— Presentation transcript:


2 Heritable Illnesses of the Navajo: Fallout of the American Indian Wars of the 19th Century

3 I have no financial relationships to disclose Steve Holve, MD

4 Objectives Define the founder effect Recognize the historical factors that led to the founder effect in the Navajo Identify heritable illnesses among the Navajo


6 “You can observe a lot by watching” Yogi Berra





11 T Kuyper

12 325,000 Tribal Members US Census 2010

13 Late Infantile Metachromatic Leukodystrophy Term AGA infant Normal newborn growth and development Loss of developmental milestones noted at 18 months- actual regression of skills Seizures began at 24 months of age

14 Late Infantile Metachromatic Leukodystrophy 30 months- Progressive neurologic degeneration Increasing spastic quadriparesis. By 36 months gastrostomy tube feeding required Multiple hospitalizations for seizure control and recurrent pneumonia Death due to aspiration pneumonia at age 6 years


16 Metachromatic leukodystrophy Autosomal recessive disorder of sphingolipid metabolism Deficiency of lysosomal enzyme arylsulfatase A Absence of ARSA leads to accumulation of sulfatides which causes progressive demyelination Occurs worldwide in 1/40,000 births Why 8 MLD cases in Tuba City in 18 years?

17 Hmmm…..That’s Odd!



20 Founder Effect a gene rare in the general population occurs in a small, isolated, rapidly expanding population which leads to increased gene frequency and increased frequency of the disease in that population


22 Examples of the Founder effect Religion - The Hutterites and the Amish Ethnicity - French Canadians and Ashkenazi Jews Geography - island populations



25 Captured

26 The Long Walk

27 Fort Sumner Imprisonment 1864- 1868



30 Population Movement and MLD Ancestors

31 Conditions Favoring the Founder Effect in the Navajo Population reduction during the Long Walk from 8,000 Navajo to 4,000 Geographic Isolation of 1,000 Navajo who fled to western reservation Subsequent rapid population increase –Navajo population increased 60 fold in 6-7 generations vs. 8 fold for U.S. population

32 Unique Single Base Mutation in Navajo MLD G to A transition in first nucleotide of intron 4 in ARSA gene

33 Population Bottleneck in the Western Navajo No MLD seen in other Athabascan groups No MLD seen in Eastern Navajo New ARSA gene frequency of MLD in western Navajo after 1868 Estimated gene frequency of 1/25 Estimated incidence of MLD 1/2500 births

34 Yupik with MLD Journal of Inherited Metabolic Disease 1995, Volume 18, Issue 3, pp 326-332Issue 3, pp 326-332 Metachromatic leukodystrophy among southern Alaskan Eskimos: molecular and genetic studies M. Pastor-Soler, E. M. Schertz, M. A. Rafi, G. de Gala, D. A. Wenger M. Pastor-Soler, E. M. Schertz, M. A. Rafi, G. de Gala, D. A. Wenger Same single base pair mutation as the Navajo


36 Possible MLD Connection of Yupik and Navajo ARSA mutation in central Asia Admixture of Athabascan and Yupik in Alaska in the past New equilibrium of gene frequencyin western navajo after long walk as MLD not seen in other Athabascan populations Founder effect for MLD in Yupiks

37 Everyone has 6-8 deleterious autosomal recessive genes... “Where are the other diseases?” Anonymous but highly respected Southwest Geneticist

38 Diseases of the Founder Effect in the Navajo Metachromatic Leukodystrophy Severe Combined Immunodeficiency Syndrome Navajo Neurohepatopathy Microvillous Inclusion Disease Athabascan Brainstem Dysgenesis Oculocutaneous Albinism Type 2 Navajo Poikiloderma

39 Severe Combined Immunodeficiency (SCID) T and B cell dysfunction Low lymphocyte counts (ALC < 2,000) Low mixed lymphocytic culture stimulation Markedly low IgA, IgG and IgM Absent thymus

40 SCID – Absent Thymus

41 The “Boy in the Bubble”

42 SCID clinical presentation Mouth and genital ulcers in child< 6mos of age Recurrent/refractory thrush Chronic diarrhea Failure to thrive Recurrent or disseminated infection Fatal before age one year if untreated

43 Oral and Genital Ulcers Arch Dermatol. 1999;135(8):927-931 Cowan et al


45 SCID-A now known to also occur in 4 Apache tribes in the Southwest unique single base pair change (A to C) in exon 8 of Artemis gene on chromosome 10p Unique base pair mutation in all Athabascan patients consistent with a founder effect

46 Athabascan SCID Incidence Overall SCID worldwide incidence 1/100,000 Initially, iIncidence in Navajo felt to be 1/10,000 births (Jones et al in 1991 Data from 1985 to present suggests about 1/2,000 live births (Dr. Diana Hu, very personal communication) Is rate increasing? Detection better?

47 Navajo Infant Mortality Rates

48 Microvillous Inclusion Disease

49 Intractable Secretory Diarrhea Intestinal Villus Atrophy Microvilli as intracytoplasmic inclusions Unique shared single base pair mutation of MYO5B in all Navajo children

50 Microvillous Inclusion Disease Mutations in myosin Vb found in 10 patients with MVID Five Navajo patients all homozygous for a single base pair mutation in exon 16 causing substitution of leucine for proline Parents all heterozygote for this mutation Speculation that is area is critical for folding of protein AJMG: 146A, 2008

51 Microvillous Inclusion Disease First case on Navajo diagnosed in 1990 Likely prior cases died and signed out as neonatal sepsis or severe diarrhea and dehydration Worldwide incidence of 1/1,000,000 Western Navajo incidence of 1/2,000

52 Navajo Infant Mortality Rates

53 Navajo Neurohepatopathy (NNH) First described in 1967 by Appenzeller and Snyder Found in Navajo on the western Reservation Initial controversy as to etiology: uranium and heavy metal exposure vs heritable illness

54 NNH Diagnostic Criteria Clinical presentation –Sensory Neuropathy –Motor Neuropathy –Corneal Anesthesia –Liver Disease –Metabolic or infectious disease derangement –CNS demyelination on radiologic imaging 4/6 or 3/6 and sibling with NN

55 Corneal Ulceration secondary to loss of sensation

56 Claw Hand Deformity secondary to motor neuropathy

57 Liver Disease in NNH neonatal hepatitis fulminant liver failure in childhood cirrhosis hepatocellular carcinoma common feature - elevated GGT

58 Ratio of Mitochondrial/Nuclear DNA Hepatology (2001)34(1)119


60 MtDNA Depletion Syndromes and MPV 17 Sequenced genes associated with Mt DNA depletion Syndromes Mitochondrial inner membrane protein Found in chromosome 2p21-23 Absence or malfunction causes OXPHOS failure and mitochondrial depletion Mutations found in 3 families (Italy, Canada and Morocco) with hepatocerebral mtDNA depletion syndromes clinically similar to NNH Spinazzola NatGenet 2April2006

61 Navajo Neurohepatopathy is caused by a mutation in the MPV17 Gene Homozygosity mapping linked to 2p24 Focused on MPV17 gene Homozygous Exon 2 R50Q mutation Same missense mutation found in all 6 NNH patients confirming disease is likely due to founder effect Karadimas AJHG:79:2006

62 Athabascan Brainstem Dysgenesis Homeobox A1 Deficiency Horizontal Gaze Palsy Central Hypoventilation Sensorineural Deafness Developmental Delay Seizure Disorder Cardiac Outflow Tract Anomalies

63 Horizontal Gaze Palsy


65 Athabascan Brainstem Dysgenesis Similar syndrome reported in Turkish and Saudi children First non-lethal homeobox protein mutation found in humans All Navajo patients share a unique single base pair mutation c/w founder effect Different base pair mutation found in Saudi and Turkish children

66 Oculocutaneous Albinism

67 Oculocutaneous Albinism Type 2 skin and hair hypopigmentation visual impairment 122.5 kb deletion in the p gene unique to Navajos

68 OCA 2 and the Founder Effect No benefit to albinism in the sunny west No known heterozygote benefit Temporary increase in gene frequency due to a founder effect

69 Navajo Poikiloderma

70 Immune Deficient Cyclical neutropenia Decreased neutrophil killing power Recurrent sinusitis, pneumonia and eventually bronchiectasis Develops hypo and hyperpigmented areas and telangiectasisas

71 Heritable Diseases- Incidence

72 Genetic Bottlenecks Bottleneck in migration to Southwest associated with SCID and Hox A1 and Navajo Poikiloderma These illnesses are seen in Navajo and Apache Bottleneck of Long walk associated with OCA-2, MLD, NNH and MVID. These illnesses are seen only in the Navajo and especially on the western side of the Navajo Nation

73 WHO Criteria Screening Condition an important health problem Cost of case finding reasonable Recognizable in latent phase Effective treatment available Acceptable to population tested

74 Genetic Screening in the Navajo SCID-A –Early identification clearly changes outcome –culturally acceptable- Navajo IRB approved newborn screening study –technologically possible –T cell receptor excision circles (TREC) on dried blood spots; absent TREC suggests T-cell dysfunction –Affordable


76 Single Gene Examples of the Founder Effect Cystic Fibrosis in the Zuni Congenital Adrenal Hyperplasia in the Yupik Eskimo Glutaric aciduria type I in the Cree Scleroderma in the Oklahoma Chocktaw

77 Founder Effects in Global Health As infant mortality falls in low resource countries it is likely that other rare heritable illnesses may become more noticeable WHO screening criteria can be applied to determine what interventions, if any, should be put in place

78 Thanks to… Morton Cowan/Lanying Li- UCSF Anthony Hayward/Ron Sokol- Univ. of Colo. David Wenger- Thomas Jefferson Univ. Russ Snyder/Otto Appenzeller/Carol Clericuzio-UNM Irwin Arias- Tufts/NIH Tuan Vu- Cornell Chris Cunniff/Bob Erickson- Univ. of Az.

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