Autosomal Recessive Disorders Flashcards

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1
Q

What is the mnemonic of Autosomal Recessive disorder?

A

WHAT CAN FUSSY GAME DO

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2
Q

What are the Autosomal Recessive disorders?

A

W = Wilson’s disease

H = Haemochromatosis

Hurler syndrome

Hallervorden-Spatz disease

A = Ataxia Telangiectasia

T = Thalassemia (Beta)

Tay-Sach’s disease

C = Cystic fibrosis

Congenital Adrenal Hyperplasia (CAH)

Crigler Najjar syndrome

A = Abetalipoproteinaemia

Albinism

Autoimmune polyendocrinopathy syndrome (APS) type 1

N = Niemann-Pick disease

F = Freinreich’s ataxia

Familial mediterranean fever

Fanconi’s anaemia

U = (all -Uria) Phenylketonuria

Alkaptonuria

Cystinuria

Homocystinuria

Maple syrup urine disease

S = Storage disorders (Lysosomal, Glycogen, Lipid)

Syndrome Bartter’s (Bartter’s syndrome)

Syndrome Rotor (Rotor syndrome)

Syndrome Lawrens (Lawrens Moon Biedl syndrome)

S = Sickle cell anaemia

Y = MucopolYsaccaridosis (All, like Hurler’s; except Hunter)

G = Galactosemia

Gaucher’s disease

Gunther disease

Gilbert syndrome

Giltelman’s syndrome

G6PD deficiency (Von Gierke’s disease)

A = Adrenal hyperplasia (Congenital, CAH)

M = Muscular: atrophies, limb girdle muscular dystrophy

E = Emphysema (Alpha 1 Antitrypsin Deficiency)

Elasticum, pseudoxanthoma (Pseudoxanthoma elasticum) (few are AD)

D = Dubin Johnson syndrome

Deafness

O = Oculocutaneous Albinism

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3
Q

Autosomal Recessive disorders are almost always which type?

Structural/Metabolic

A

Metabolic

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4
Q

Name 4 metabolic disorders which are X-linked recessive

A

Hunter’s disease (= Mucopolysaccaridosis or MPS type 2)

G6PD deficiency

Adenoleukodystrophy (Childhood form)

Ornithine transcarbamoylase deficiency

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5
Q

Name 6 metabolic disorders which are autosomal dominant

A

Hyperlipidaemia type II (a,b)

Familial hypercholesterolemia (=hyperlipidaemia IIa)

Hypokalaemic periodic paralysis

Hyperthermia (Malignant)

Acute intermittent porphyria (AIP)

Porphyria cutanea tarda (PCT)

Variegate porphyria

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6
Q

Hurler’s disease comes into which category of disease?

A

Mucopolysaccharidoses

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7
Q

What is the inheritence pattern of mucopolysaccharidoses?

A

All mucopolysaccharidoses : Autosomal recessive

Hurler’s disease: Autosomal recessive

Hunter’s disease: X-linked recessive

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8
Q

Who are affected by autosomal recessive disorders?

heterozygotes/homozygotes/both?

A

Only homozygotes are affected and manifest the disease

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9
Q

Who are affected by autosomal recessive conditions?

Male or female?

A

Both

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10
Q

What is the carrier status for autosomal recessive disorders?

A

All heterozygous are carrier

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11
Q

Do autosomal recessive disorders manifest in every generation?

A

NO

Autosomal recessive do NOT manifest in every generation; may skip a generation

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12
Q

What are the possible combinations of genotype in parents/couple in recessive conditions?

A

Heterozygote carrier + normal

Heterozygote carrier + Heterozygote carrier

Heterozygote carrier + Homozygote (affected)

Homozygote (affected) + Homozygote (affected)

Homozygote (affected) + normal

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13
Q

If one parent is heterozygote carrier + another normal, what are the chances among children?

(can use pen & paper)

A

Each child has 0% chance of being affected (homozygote)

Each child has 50% chance of being a carrier (heterozygote)

Each child has 50% chance of being a normal

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14
Q

If both parents are heterozygote carriers, what are the chances among children?

(can use pen & paper)

A

Each child has 25% chance of being affected (homozygote)

Each child has 50% chance of being carrier (heterozygote)

Each child has 25% chance of being normal (not carrier/affected) child (i.e. genotypical child)

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15
Q

If one parent is heterozygote carrier + another homozygote (affected), what are the chances among children?
(can use pen & paper)

A

Each child has 50% chance of being affected (homozygote)
Each child has 50% chance of being carrier (heterozygote)

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16
Q

If both parents are homozygotes (affected), what are the chances among children?
(can use pen & paper)

A

Each child has 100% chance of being affected (homozygote)

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17
Q

If one parent is homozygote (affected) + another normal, what are the chances among children?
(can use pen & paper)

A

Each child has 0% chance of being affected (homozygote)

Each child has 0% chance of being normal

  • *All the children** will be carrier (heterozygote) =
  • *100% chance** of having a carrier (heterozygote) child
18
Q

How many mutated copies/alleles of the autosomal gene is needed to manifest the disease?

A

2 (two)

19
Q

Autosomal recessive conditions are almost always metabolic,

But, as an exception, which are structural?

A

AR structural conditions:

Ataxia telangiectasia (inherited ataxia)

Friedrich’s ataxia (inherited ataxia)

Oculocutaneous albinism

20
Q

What is the inheritence of lipid storage disorders?

A

Autosomal recessive

21
Q

What are the lipid storage diseases?

A

Tay-Sach’s disease

Gaucher disease

Niemann-Pick disease

22
Q

What is the underlying pathology of Gaucher disease?

A

Deficiency of glucocerebrocidase enzyme >>>>> excess glucocerebrocide accumulates in cells, organs

Increased acid phosphatase activity

23
Q

What are the common features of Gaucher’s disease?

A

Anaemia >> fatigue

Low platelets >> bruising

Hepatomegaly

Splenomegaly

24
Q

What is the underlying pathology in Tay-Sach’s disease?

A

Excess ganglioside accumulation in brain >>>>> premature nerve cell death

25
Q

In which race, Tay-Sach’s is more common?

A

Askenazi Jews population

26
Q

What are the usual manifestations of Tay-Sach’s?

A

At 7months of age >>>>> Low mental & physical abilities

At around 4years >>>>> Death

27
Q

Inheritance of G6PD deficiency

A

G6PD deficiency (favism) >>> X-linked recessive

G6PD deficiency (Von Gierke’s disease) >>> Autosomal recessive

Only G6PD deficiency (if asked) >>> Consider X-linked recessive (more common)

28
Q

What special inheritance may be seen in hereditary haemochromatosis?

A

Pseudodominant

29
Q

What is pseudodominant inheritance in hereditary haemochromatosis?

A

As carrier frequency is high (>1 per 10) >>> often partner of an affected person is conincidentally a carrier >>> 50% of his or her offspring will have a genotype of clinically affected haemochromatosis = so, psueo-dominant (/vertical dominant transmission is observed)

30
Q

In haemochromatosis, if both alleles are mutated, will all become symptomatic?

A

NO. Only a few of them will be symptomatic

31
Q

What is the penetrance of haemochromatosis in different sex?

A

Penetrance is higher in males than females

32
Q

What is Hallervorden Spatz disease?

A

It is rare neurodegenerative condition due to increased iron accumulation

33
Q

Hallervorden spatz disease: genetic defect

A

Chromosome 20

Gene PANK2

Encodes: pantothenate kinase 2

34
Q

Hallervorden Spatz disease: features

A

Childhood or Adolescence

  • Pyramidal/extrapyramidal signs
  • Dementia
  • Optic atrophy

MRI: Eye of the tiger signs (due to increased Fe in basal ganglia)

35
Q

What is Pseudoxanthoma elasticum?

A

Abnormal elastic fibres

36
Q

Pseudoxanthoma elasticum: Features

A
  • Retinal angioid streaks
  • Plucked chiken skin appearance >> small yellow papules on the neck, antecubital fossa and axilla
  • Cardiac: mitral valve prolapse (MVP)
  • GI haemorrhages

(Mitral valve prolapse is also seen in Marfan syndrome, Fragile X syndrome)

37
Q

What is Galactosaemia?

A

Intracellular accumulation of galactose-1 phosphate

38
Q

Galactosaemia: Enzyme deficiency

A

Deficiency of galactose-1-phosphate uridyl transferase

39
Q

Galactosaemia: Features

A
  • Jaundice
  • Cataracts
  • Failure to thrive
  • Hypoglycaemia (after exposure to galactose)
  • Hepatomegaly
  • Fanconi syndrome
40
Q

Galactosaemia: diagnosis

A

Reducing substances in urine

41
Q

Galactosaemia: management

A

Galactose free diet