3. • PORPHYRIAS - metabolic disorders caused by altered activities of
enzymes within the heme biosynthetic pathway
• Greek term - purple discoloration of body fluids during an acute attack
• Challenging to diagnose
rare
symptoms are nonspecific
INTRODUCTION
4. • PORPHYRINS - water soluble, nitrogenous biological pigments.
(biochromes)
• Examples of its derivatives include – chlorophyll in plants, haemoglobin
in blood, cytochromes for oxidative process, catalase for hydrogen
peroxide damage.
• Structure – 4 pyrrole rings, iron atom in centre
• Absorb light intensely at 410 nm – Excitation; 615 nm - Emission.
INTRODUCTION
5. • Heme synthesis - occurs mainly in bone marrow (for hemoglobin) and liver
(for cytochrome synthesis)
• Porphyrias - 8 genetically distinct inherited enzyme deficiency disorders –
resulting in defects in heme synthesis
• Inheritance: AD/ AR/XL (exception- PCT is sporadic)
• Acute attacks - characterized by excretion of high levels of porphobiliogen,
ALA and porphyrins
HEME BIOSYNTHESIS
6. • Rate limiting step in liver - ALA synthase
• 2 isoenzymes - ALAS1 in liver, ALAS2 in erythroid cells
• 15% heme - synthesized in liver - cyt p450 enzymes, hemoproteins
ALAS1 - under negative feedback by “free” heme (controls
transcription, synthesis and transport of
ALAS1)
- inducible by drugs (cyt p450 enzyme inducers),
nutrition, stress
• 85% heme - synthesized in erythroid cells - hemoglobin
ALAS2 - not under negative feed by hemin
HEME BIOSYNTHESIS
14. 1. all are AD except ADP – AR – very rare
• Acute intermittent porphyria (AIP) - (the most common and
prototype)
• Delta-aminolevulinic acid (ALA) dehydratase (ALAD) porphyria (ADP)
• Hereditary coproporphyria (HCP)
• Variegate porphyria (VP)
2. Acute and chronic symptoms due to effects on the nervous system.
- neuropathic abdominal pain
- Motor weakness, sensory loss and pain in the back, chest, and
extremities, and autonomic changes - tachycardia, hypertension
3. HCP and VP may also present with blistering skin
ACUTE HEPATIC PORPHYRIA
17. • Autosomal dominant
• Hepatic porphyria
• Results from “half normal” enzyme activity of HMB synthase
• Most common acute porphyria
• Usually latent before puberty
Prototype - AIP
18. • Unclear
• ALA, PBG – neurotoxic
• GABA analog/ interact with GABA receptors
• Heme deficiency in nervous system
Pathogenesis - AIP
19. Fasting- activation of peroxisome proliferator-activated receptor γ
coactivator 1α (PGC-1α)
Increased ALAS1 transcription
Increased heme biosynthesis
Increased synthesis of porphyrins
Role of fasting
Links nutritional status with precipitation of acute attack of porphyria
Thus – carbohydrate intake ameliorates attack
20. • Highly variable
• Low clinical expression
• Onset usually after puberty
• Less than 10% have acute attacks
• Majority of heterozygotes- clinically asymptomatic
(latent/presymptomatic) with increased urine ALA and PBG
• Trigger- hormonal/ metabolic/ dietary/ environmental factors
• Abdominal pain, central nervous system abnormalities, and peripheral
neuropathy are described as a "classic triad" that should suggest acute
porphyria
Clinical profile
21. • Neurovisceral disturbances
• Visceral:
• Abdominal pain- Most common symptom (85-95%)
unremitting, poorly localized, steady, cramping, a/w nausea,
vomitings
• Constipation, Ileus, abd distension, decreased bowel sounds
• No tenderness/ fever/ leukocytosis – (s/o neurologic origin- not
inflammatory)
• Dysuria, bladder dysfunction, urine retention
• Sympathetic over-activity:
• tachycardia, hypertension, fine tremors, sweating
Clinical profile
22. • Neurological-
• Common symptoms- Pain in limbs, back, chest, neck (50-70%)
Paresis – (40-70%)
CNS- anxiety, insomnia, depression, etc (40-60%)
• Cranial nerves- most commonly 7th, 10th > Optic nerves
• Peripheral neuropathy- primarily motor – axonal degeneration
• Muscle weakness- Proximal onset, progress to respiratory/ bulbar
• Paresis –asymmetric and focal
• DTR –brisk/ normal early- reduced/ absent late
• Sensory – extremity pain and paresthesia, loss of sensation
• Complete recovery- slow
Clinical profile
23. • Endogenous steroid hormones – symptoms rare before puberty/ commoner in
females/ premenstrual attack and prevention by GnRH/ exacerbation with OCP
• Drugs- most AED, barbiturates, sulfonamides, rifampin, progestins
• Intercurrent infections
• Major surgery
• Low calorie diet- carbohydrate restriction
• Increase demand for heme synthesis – induce hepatic ALA
Precipitating factors
24. Recommendations for the Diagnosis and Treatment of the
Acute Porphyrias
Ann Intern Med. 2005;142:439-450.
25. • Seen in 10-20%
• Central neurological manifestation of AIP or
• Hyponatremia related (SIADH/ sodium depletion)
• Anti-seizure medication- avoid barbiturates
• AED of choice-
• Gabapentin, vigabatrin, benzodiazepines relatively safe
• Correct hyponatremia/ hypomagnesemia
Seizures
26. • PBG level >10 mg per g creatinine [or >10 mg/L - treatment with
hemin should be initiated without delay if clinical manifestations are
severe
• PBG level <5 mg per g creatinine or <5 mg/L- consider other
differential diagnosis
• Normal urinary excretion of PBG is <2 to 4 mg (<9 to 18 micromol) per
day
27. • Total porphyrins are elevated in all four AHPs.
• In HCP and VP, total porphyrins may remain elevated for a longer
period of time than PBG.
• However, urine porphyrin elevations are very nonspecific and occur in
many medical conditions other than porphyrias.
• ALA can also be measured but is not essential at screening.
• Normal urinary excretion of ALA is <7 mg (<53 micromol) per day. In
an acute attack of AIP, HCP, or VP, urinary ALA excretion is elevated,
but generally less so than PBG (when expressed in mg).
28. • Urine PBG and ALA: always markedly increased (20-200mg/24hrs) in acute attack
• Normal urine PBG – excludes Acute porphyria
(exception –ALA dehydratase deficient porphyria - ALA)
• Urine PBG correlates with clinical improvement in symptomatic patients
• Biochemically proven case - acute attack diagnosed on basis of clinical
features – no need of reconfirmation
Normal urine PBG- 0-4mg/24hrs, 0-18μmol/24hrs
Normal urine ALA excretion- 0-7mg/24hrs; 0-53 μmol/24hrs
Biochemical confirmation – 1st line tests
29. Glycine
+
Succinyl CoA
δ-ALA
δ-ALA Synthase
PBG x 4
δ-ALA Dehydratase
HMB UPG III
UPG III cosynthase
CPG III
UPG III decarboxylase
CPG oxidase
PPG IX
PPG oxidase
Protoporphyrin IX
Fe2+
Ferrochelatase
HEME
HMB synthase
MITOCHONDRIA
CYTOPLASM
1. XLP
2. ADP
3. AIP
4. CEP 5. PCT
6. HCP
7. VP
8. EPP
Acute intermittent porphyria
30. • Enzyme analysis - erythrocyte HMB synthase :
• Half normal levels - confirmatory
• Normal level - doesn’t exclude AIP
(liver and other organs might still be deficient)
• Helps screening family members
• Urine porphyrin – increased in AIP, HCP, VP
• Plasma porphyrin – normal or increased in AIP, HCP (High in VP)
• Fecal porphyrin - normal/ mild increase in AIP (increased in HCP, VP)
Biochemical confirmation – 2nd line tests
31. • HMBS gene
• Point/ splice site mutations, family specific
• Confirms diagnosis in patients with attacks, identify at-risk family members
• Variant form – mutation impairing exon1 splicing
• prevention of housekeeping (ALAS1) but not erythroid specific transcript
• Deficient activity in liver but erythrocyte levels are normal
• Increased PBG, normal erythrocyte HMB-synthase
• Homozygous dominant AIP- rare, <2% enzyme activity
• No modifying/ predisposing genes identified for pt with chronic attacks
Mutation analysis
34. • Mechanism- repress hepatic ALAS
• Carbohydrate loading- IV 10% glucose (at least 300-500gm daily)
• Nutritional replacement
• IV glucose alone- only for mild attack
(mild pain, no paresis, no hyponatremia)/
until hemin is available
• Risk- hyponatremia
Intravenous glucose
35. • Mechanism- repress hepatic ALAS
• Dose: 3-4mg/kg/day IV for 4 days
• Start for moderate to severe attacks, mild attack not responding to
carb loading in 1-2 days
• Complication- phlebitis at infusion site
• Reconstitution with albumin- enhance stability
• Clinical improvement 1-2 days after attack
• Not effective for chronic symptoms that persist between attacks
• Frequent hemin - risk of iron overload- monitor ferritin
Hemin treatment
36. Before starting treatment, obtain the following samples:
• Spot urine porphyrins
• Plasma porphyrins
• Stool porphyrins
GIVOSIREN - is an RNA interference therapy that reduces production of
ALA and PBG by downregulating the first enzyme in the heme synthetic
pathway, ALAS1.
• may be used as preventive therapy in individuals who have frequent
attacks of AHP
37. • Abdominal pain may disappear in hours
• Paresis- improves in days gradually
complete recovery may take years
• Biochemical – ALA and PBG decrease over few days after iv hemin
Resolution of acute attack
39. • Patient education
• Identify precipitating factors
• Avoid drugs that can induce exacerbation
• Maintain adequate nutrition
• Women with cyclic attacks- GnRH analogs
• Pregnancy - well tolerated
• Recurrent non cyclic attacks - weekly/ biweekly hemin infusions -
monitor ferritin levels
• Unremitting symptomatic disease - Orthotopic liver transplant
Prevention of acute attacks
40. • Identify at - risk relatives
• Offer genetic counselling
• Diagnosis - detection of family’s HMBS mutation
• Offer asymptomatic heterozygote counselling to avoid drugs, fasting,
hormones, etc
Asymptomatic family members
41. • Acute porphyrias - life threatening neurovisceral symptoms
• Mimic many acute medical and psychiatric conditions- Need high
index of suspicion for diagnosis
• Prompt diagnosis and treatment - prevents severe or chronic
neuropathic symptoms
• Delayed treatment- more advanced neuronal damage- slower to
recover
42.
43. chronic blistering
cutaneous lesions
on sun-exposed
areas
often with
scarring and
pigment changes
severe disease –
CEP - high
porphyrin levels -
photomutilation,
with loss of facial
features and
digits.
Chronic
Blistering
Cutaneous
Porphyrias
Porphyria cutanea tarda (PCT),
(the most common and
prototype)
Congenital erythropoietic
porphyria (CEP)
Hepatoerythropoietic
porphyria (HEP)
Variegate porphyria (VP)
Hereditary coproporphyria
(HCP) - skin manifestations
are rare
Chronic Blistering Cutaneous Porphyria
44. • PCT is the most common porphyria
• It is due to acquired inhibition of hepatic uroporphyrinogen decarboxylase (UROD).
• It is a condition associated with iron that usually presents in adults with blistering
skin lesions.
• Chronic blistering, scarring, and pigment changes on sun-exposed areas - dorsal
hands and less often the face, neck, ears, and feet.
• Neurovisceral manifestations are absent
• Susceptibility factors include varying combinations of alcohol or estrogen use,
smoking, hepatitis C, HIV infection, HFE (hemochromatosis) mutations, or
heterozygous UROD mutations.
• Rare affected children are likely to have UROD mutations and to have received
chemotherapy for leukemia or other neoplasms
• Exclude other less common blistering cutaneous porphyrias and pseudoporphyria,
before initiating specific therapy - phlebotomy and low-dose Hydroxychloroquine -
effective exclusively in PCT.
Porphyria Cutanea Tarda
50. • Avoidance of sunlight is advised but is not usually of immediate
benefit
• Skin fragility contributes to blister formation and is slow to resolve.
• Superadded bacterial infections, which should be treated promptly.
• PCT is the most readily treated porphyria - responds well to
treatments that reduce hepatic iron, such as phlebotomy, or to low-
dose hydroxychloroquine, which mobilizes porphyrins from the liver.
Treatment
51. • Congenital Erythropoetic Porphyria (CEP) is an uncommon disorder of
the heme biosynthesis pathway with deficiency of enzyme -
uroporphyrinogen III synthase (UROS).
• It is AR disorder. However, X-linked gene globin transcription factor1
(GATA1 ) has also been reported.
• Uroporphyrin I accumulation in bone marrow, erythrocytes, plasma,
and urine is the biochemical hallmark of the disease.
CEP
52. • Pink to dark reddish urine is usually noted shortly after birth.
• Usual age of presentation commonly with brown to reddish coloured
urine is early infancy
• Manifestations include reddish coloured urine and bullous vesicular
lesions of sun-exposed areas which, when infected lead to
progressive photomutilation.
• Prevention of skin blistering and eye damage by avoidance of
sunlight, protective clothing and sunglasses, sunscreen lotion is vital.
Hematopoietic stem cell transplantation is curative.
Clinical features
53. • 2.5 yr boy
• intermittent episodes of reddish urine for 5 months
• vesicular rash over exposed areas which healed with scarring for 3
months.
• O/E - underweight with multiple maculopapular healed scars seen over
face, dorsum of hands and trunk brownish deformed teeth and pallor.
• Investigations –
• microcytic hypochromic red cells (MCV-70.5fl, MCH-24.7pg/cell) , no
anemia (Hb- 12.6g/dl).
• LDH (593U/L) elevated, plasma hemoglobin was normal, there was no
evidence of hemoglobinuria and direct coombs test (DCT) was
negative.
Case Scenario
54. • Urine porphyrin studies showed significantly elevated total urinary
porphyrins.
• There was significantly elevated levels of uroporphyrin and uro/copro
ratio, with mildly elevated levels of heptacarboxylporphyrin,
hexacarboxylporphyrin, pentacarboxylporphyrin and coproporphyrin,
uroporphyrin I >>> uroporphyrin III; and the
uroporphyrin/coproporphyrin ratio was elevated.
• In presence of predominant photosensitive and dental manifestations
with elevated urinary porphyrins and specific pattern of excretion,
Congenital Erythropoetic Porphyria (CEP) was confirmed.
Case Scenario
57. • Patients with protoporphyria develop immediate photosensitivity
(usually within minutes of sunlight exposure)
• Manifests with acute pain, which compels them to seek shelter from
light.
• With more prolonged exposure, pain may be followed by erythema,
swelling, and systemic symptoms that may last for several days, but
with few if any blisters or lasting skin changes.
• Hepatobiliary manifestations - Gallstones (containing
protoporphyrin), severe cholestatic liver disease (<5%) due to excess
protoporphyrin presented to the liver for biliary excretion.
EPP
61. • Sun avoidance - to prevent acute photosensitivity reactions
• Beta-carotene - originally developed for treatment of EPP
• Afamelanotide - alpha-melanocyte stimulating hormone (alpha-MSH)
• Increases skin pigmentation by increasing melanin production
• It was approved by the FDA for this indication in 2019.
Treatment
64. OVERVIEW
ALA, PBG – detected by calorimetry, modified Ehrlich’s reagent, DMAB
Uroporphyrins, hepta, hexa, pentaporphyrins – HPLC with fluorescence detection
Copro, Protoporphyrins – by HPLC
False high ALA –
Lead intoxication
Tyrosinemia
Drugs – Teicoplanin, coamoxyclav
False high porphyrins –
Alcohol intake
Stress
65. • The risk of inheritance depends on the type of porphyria.
• For AD type, the risk of recurrence will be 50% in each pregnancy if
one of the parent also has the disease. However, some patients may
remain asymptomatic throughout life.
• For AR type, the recurrence risk will be 25% in each pregnancy.
GENETIC COUNSELLING
66. • The disease can have variable presentations.
• Some types are debilitating – and can lead to life threatening
complications.
• Prenatal testing can be done.
• The molecular diagnosis should first be done in the affected person.
• Then fetal testing by Invasive methods – CVS at 11-13 weeks or
amniocentesis at 16-18 weeks can be done by Sanger sequencing of
fetal DNA.
PRENATAL TESTING
67. • Porphyrias are rare disorders with nonspecific clinical manifestations
similar to those of many other more common diseases.
• Their diagnosis and appropriate treatment are often delayed.
• Biochemical first-line screening tests are sensitive for diagnosis of
these disorders, and additional second-line testing readily
differentiates the various types of porphyria.
• Effective treatment is available but will not be provided unless a
diagnosis is made.
SUMMARY
ALAS occurs in two forms- increased ALAS1 expression is important in the acute hepatic porphyrias. erythroid-specific form, termed ALAS2, is produced only in bone marrow erythroblasts
ALA and PBG are commonly referred to as porphyrin precursors
HMB synthase = PBG deaminase. Remaining HMB changes to UPG I
Mention hepta, hexa, penta porphyrinigen – these and uro in urine – pink fluorescence to UV light – HPLC with fluproscence. ALA, PBG –calorimetry, modified Ehrlich’s reagent DMAB.
Copro and protoporphyrins – less polar – bile – excreted in faeces
Depending on where the damaging porphyrin compound / precursors first build up in the body – BM or liver
Build up in skin and interact with sunlight. Nervous system.
screening for AHP (by measuring urine porphobilinogen [PBG] and porphyrins) should be considered even when suspicion is not particularly high.
Clues - Multiple previous hospitalizations with abdominal pain and negative evaluations
Accompanied by neurologic or psychiatric symptoms
Multiple abdominal surgeries without definite diagnoses or benefits should also trigger testing for AHP.
screening for AHP (by measuring urine porphobilinogen [PBG] and porphyrins) should be considered even when suspicion is not particularly high.
Clues - Multiple previous hospitalizations with abdominal pain and negative evaluations
Accompanied by neurologic or psychiatric symptoms
Multiple abdominal surgeries without definite diagnoses or benefits should also trigger testing for AHP.
screening for AHP (by measuring urine porphobilinogen [PBG] and porphyrins) should be considered even when suspicion is not particularly high.
Clues - Multiple previous hospitalizations with abdominal pain and negative evaluations
Accompanied by neurologic or psychiatric symptoms
Multiple abdominal surgeries without definite diagnoses or benefits should also trigger testing for AHP.
screening for AHP (by measuring urine porphobilinogen [PBG] and porphyrins) should be considered even when suspicion is not particularly high.
Clues - Multiple previous hospitalizations with abdominal pain and negative evaluations
Accompanied by neurologic or psychiatric symptoms
Multiple abdominal surgeries without definite diagnoses or benefits should also trigger testing for AHP.
screening for AHP (by measuring urine porphobilinogen [PBG] and porphyrins) should be considered even when suspicion is not particularly high.
Clues - Multiple previous hospitalizations with abdominal pain and negative evaluations
Accompanied by neurologic or psychiatric symptoms
Multiple abdominal surgeries without definite diagnoses or benefits should also trigger testing for AHP.
Blistering cutaneous porphyrias are largely chronic, and treatment is seldom urgent.
Blistering cutaneous porphyrias are largely chronic, and treatment is seldom urgent.
Blistering cutaneous porphyrias are largely chronic, and treatment is seldom urgent.
Blistering cutaneous porphyrias are largely chronic, and treatment is seldom urgent.
Blistering cutaneous porphyrias are largely chronic, and treatment is seldom urgent.
