1. Putting the “Heme” back in “Heme-Onc” Acute look into Porphyrias: AIP
David Bolos, PGY4
Hematology Oncology Fellow
03/29/2016

2. Chief Complaint Abdominal pain Nausea/Vomiting Muscle Weakness
Numbness/Tingling
Anxiety

3. History of Present Illness
32 year old female, relatively healthy
Severe Abdominal Cramping which coincides around the time of her periods every month
Symptoms started in 2008, after the birth of her second child
In 2008, ICU stay for severe hyponatremia requiring intubation, Na level 110 reportedly

4. History of Present Illness
After 2008 hospitalization, monthly severe abdominal pain episodes associated with N/V, muscle weakness, parasthesias, anxiety
ROS (+) HA, N/V, Generalized Muscle Weakness, Parasthesias of Arms/Legs, Sharp generalized abdominal Pain, non-focal, fatigue, tearful, anxious
ROS (-) CP, Palpitations, SOB, Cough, F/C, Night Sweats, Melena, Hematochezia, Jaundice, Pruritis, dysuria, pregnancy, loose stools, seizure like activity, syncope

5. Past Medical History
Hyponatremia Episode 2008, requiring Intubation (likely 2/2 SIADH)
Low Vitamin D
History of Quant Gold (+)
Chronic Paresthesia's/Neuropathy
Bowel perforation during procedure
GERD

6. Past Surgical History Dental extraction EGD/Colonoscopy
Bowel Perforation, s/p repair
C - section x2

7. Family History Reportedly 2 cousins with “chronic abdominal pain”
No other known medical problems

8. Medications/Allergies
Aspirin
Lyrica
Morphine
Lupron (in past)
NO MEDICAL ALLERGIES

9. Social History Married, 2 children
Lives in Los Angeles with her husband
Moved to LA 1 year ago
Not employed
Denies T/A/D History

10. Vitals/Physical Exam T 36.8, HR 106, RR 14, BP 98/52, 98% RA
Gen: anxious, tearful, appears in distress
HEENT: grossly normal
CV: Tachycardic, normal s1s2, no m/r/g, no JVD
Resp: CTA B/L, no wheeze, crackles, rhonchi
Abd: (+) guarding, (-) rebound, diffusely tender to palpation (non-focal), Normal Bowel Sounds, no HSM appreciated, no masses
Ext: no edema, peripheral pulses intact
Neuro: CN 2-12 intact, muscle strength 4/5 in upper and lower extremities (equal bilaterally), sensation to touch diminished minimally in hands and feet, coordination intact

11. Labs
CBC 6.6/10.6/31.1/105
BMP 137/4.1/108/22/6/0.8/80
LFT’s AST 20, ALT 8, Bili 0.3/0.2, Alk Phos 52
Lipase 34
HIV negative
TSH 1.2
Hep Panel Negative
INR 1.1
Urine Pregnancy Negative
Lactate 1.2
Lead Level <3
D-Dimer 503
UA negative

12. Differential Diagnosis
Acute Cholecystitis
Pancreatitis
Appendicitis
Mesenteric Ischemia
Choledocholithiasis
Cholelithiasis
IBS
Lead Toxicity
Familial Mediterranean Fever
Malignancy
Endometriosis

13. King George III, the mad king

14. Acute Intermittent Porphyria

15. Introduction
Porphyrias are metabolic disorders cause by altered activities of enzymes within the heme biosynthetic pathways. 
Alteration in enzymatic activity is usually due to an inherited mutation, however,
Porphyria Cutanea Tarda (PCT) is the most common of the porphyrias and is acquried
inhibition of uroporphyrin Decarboxylase (UROD). 

16. The Heme Biosynthetic Pathway: Putting the Heme back in Heme-Onc
Heme is made in all tissues, bone marrow and liver are the most active organs involved in overall heme synthesis 
Bone marrow accounts for >80% of daily heme synthesis (mostly utilized as the prosthetic group for Hb) 
Liver accounts for most of the rest of overall heme synthesis (primarily for production of various cytochrome P450 enzymes) 
Other important heme-containing proteins are present in various tissues (myoglobin, catalase, nitric oxide synthase) 
Enzymes and Intermediates: 
Eight enzymes and intermediates that comprise the heme synthetic pathway (see figure 1, handout) 

17. CPG-Oxidase deficiency leads to Hereditary Coproporphyria: its like AIP, but with skin findings as well (similar to Porphyria cutanea Tarda)
PPG-Oxidase deficiency leads to Variegate porphyria, similar to AIP, but with skin findings also.
Typically, the distinguishing metabolite for HCP and VP is the presence of protoporphyrin in the plasma and feces of individuals affected with VP

18. Acute Porphyrias: lead to accumulation of precursors
Under normal circumstances, heme synthesis begins in the mitochondrion, proceeds into the cytoplasm, and finishes back in the mitochondrion. However, without porphobilinogen deaminase, a necessary cytoplasmic enzyme, heme synthesis cannot finish, and the metabolite porphobilinogen accumulates in the cytoplasm

19. Regulation of Heme Synthesis:
ALAS1 (5-aminolevulinate synthase) is a mitochondrial enzyme that requires pyridoxal-5'-phosphate as a cofactor, catalyzing the conversion of
glycine + succinyl-coA to form delta-aminolevullinic acid (ALA), an amino acid committed exclusively to the synthesis
(RATE LIMITING STEP) 
ALAS occurs in two forms encoded by different genes found on different chromosomes.
ALAS1 (found in all tissues), and
ALAS2 the erythroid-specific form, is transcribed only in bone marrow erythroblasts.

20. Regulation of Heme Synthesis:
Since most of the heme synthesized in the Liver is used for production of CYPs,
induction of CYPs by drugs and other factors would lead to induction of ALAS1 through this feedback mechanism
The feedback mechanisms are important in Acute Porpyrias, which are exacerbated when hepatic ALAS1 is induced.
Acute Porphyrias may be treated with exogenous heme, which is taken up primarily in hepatocytes, where where it repletes the regulatory heme pool, down-regulates ALAS1, and ameliorates the acute attack

21. Regulation of Heme Synthesis:
Heme synthesis in bone marrow is regulated differently from that in the liver, in order to provide heme in amounts required for hemoglobin synthesis. 
The gene encoding for ALAS2 is localized to chromosome Xp11.21,
unlike ALAS1, whose expression is regulated by liver heme concentration and inhibited by adequate free heme concentration,
ALAS2 activity is constitutively expressed in erythroid cells and is upregulated by heme and by iron. 

22. Diseases associated with Alterations in Heme Biosynthetic Pathway Enzymes (see diagram 2)
ALA Synthase 1: mutations have not been described, but upregulation of hepatic ALAS1 is an important feature during exacerbations of acute hepatic Porphyrias. 
ALA Synthase 2: present in many cases of X-linked Sideroblastic Anemia. Gain of function ALAS2 mutations have been described in a variant form of EPP (Erythropoietic Protoporphyria), known as X-linked Protoporphyra
Each of the subsequent enzymes in the heme synthetic pathway is deficient in a specific type of porphyria (see diagrams)
Our focus today will be on AIP

23. Environmental and Metabolic Influences:
Lead (inhibits ALA Dehydratase), second enzyme in the pathway, displaces zinc from its binding site on the enzyme
Drugs, hormones, and nutritional alterations are important in precipitating attacks of neurovisceral symptoms in acute porphyrias,
hormonal changes associated with the luteal phase of the menstrual cycle,
drugs that increase CYP pathways. 

24. Classification of Porphyrias: Acute or Cutaneous
Reflecting the primary clinical manifestations (not completely distinct, there is overlap in some) 
Also classified as hepatic or erythropoietic, depending on whether the site of initial production and accumulation of pathway intermediates is the liver or bone marrow. 
Acute porphyrias generally give neurovisceral manifestations 
Cutaneous porphyrias, those affecting sun-exposed skin.
Divided into chronic blistering photosensitivity and
those causing acute non-blistering photosensitivity

25. Classification of Porphyrias: (handout 3)
Acute: ALA dehydratase Porphyria (ADP), Acute Intermittent Porphyria (AIP), Hereditary Coproporphyria (HCP),
ADP and AIP are neurovisceral only,
HCP and VP have neurovisceral as well as cutaneous manifestations. 
Chronic blistering photosensitivity: Congenital Erythropoietic Porphyria (CEP), Hereditary Corproporphyria (HCP), Hepatoerythropoietic Porphyria (HEP), Porphyria Cutanea Tarda (PCT), Variegate Porphyria (VP),
HCP and VP are both neurovisceral and cutaneous,
CEP, HEP, PCT are cutaneous only 
Acute non-blistering photosensitivity: Erythropoietic Protoporphyria (EPP) and X-linked Protoporpyria (XLP) 

26. Laboratory Diagnosis: (Handout 4)
Measurement of the porphyrin precursors ALA and PBG, as well as porphyrins in urine, plasma, erythrocytes, and feces is important for the diagnosis of various porphyrias. 
Acute Porphyrias Diagnosis: check urinary PBG, rapid qualitative testing should be available in-house at certain centers. 
The same urine sample should be saved for quantitative determination of ALA, PBG, and total porphyrins, to confirm the qualitative PBG results. 

27. Laboratory Diagnosis:
PBG can also be measured in plasma, which is essential if acute porphyria is suspected in a patient with advanced renal disease. 
Porphobilinogen: normal urinary excretion is less than 2-4 mg/24hr.
In an acute attack of AIP, urinary PBG excretion is markedly elevated, 5-10x the upper limit of normal. 
Three porphyrias that cause increases in PBG
(AIP, HCP, VP)
differentiated from each other by measuring erythrocyte PBG deaminase (PBGD), urinary porphyrins, fecal porphyrins, plasma porphyins, and by mutation detection 

29. Acute Intermittent Porphyria (AIP)
Acute neurovisceral porphyria resulting from a partial deficiency of the heme biosynthetic enzyme porphobilinogen deaminase (PBGD). 
Autosomal Dominant with low penetrance (family history may not be helpful at times) 
Diagnosis is challenging. Symptoms are vague/non-specific 
Other possible causes of symptoms are more likely (neuro and abdominal pain)

30. Pathogenesis: 
The liver is the major source of overproduction of heme pathway intermediates in patients with hepatic porphyrias, such as AIP
The central, peripheral, and autonomic nervous systems are affected when levels of these intermediates are elevated
Gene mutation: heterozygosity for a mutation in the gene encoding porphobilinogen deaminase (PBGD), also called hydroxymethylbilane synthase (HMBS) and previously referred to as uroporphyrinogen I synthase. 
Autosomal dominant with low penetrance 

31. Pathogenesis: 
>300 PBGD gene mutations have been recognized in AIP, all of which lead to severe loss of enzymatic activity from the mutant allele 
No convincing evidence for genotype-phenotype correlation in AIP, particular mutations do not predict disease severity (highly variable)
Disease severity is affected by environmental and other factors (as stated earlier) 
PBGD gene is transcribed as two separate splice variants, one erythroid-specific (expressed only in erythroid precursor cells), the other expressed in all cell types, including hepatocytes. 
In AIP, the PBGD mutation always affects hepatic PBGD

32. Enzymatic Defect: 
AIP mutations in PBGD/HMBS decrease activity of the PBGD/HMBS enzyme. 
Cytosolic enzyme catalyzes the 3rd step in heme biosynthesis, whereby four molecules of porphobilinogen are sequentially condensed to form HMB (see handout 1) 
HMB is unstable and is rapidly metabolized by the 4th enzyme in the pathway to uroporphyrinogen III

33. Enzymatic Defect: 
Decreased activity of the hepatic form of PBGD, rather than erythroid form, appears to be responsible for the neuronal damage that leads to AIP disease manifestations
(Liver Transplant causes marked clinical improvements) 
Symptomatic AIP does not develop in all patients with the mutation. 
In addition to reduced PBGD activity, symptomatic AIP requires a marked induction of the ubiquitous form of delta-aminolevulinic acid (ALA) synthase (ALAS1),
which is upstream of PBGD (see handout 2)
increasing precursor production. 

34. ALAS1 ALAS1 synthesis is induced by the following:
depletion of regulatory hepatic heme pool, which is further favored by a partial deficiency of PBGD
drugs, sex hormones, CYP inducers 
caloric an carbohydrate restriction 
metabolic stress , acceleration of heme destruction 

35. Neurological Dysfunction:
Central, peripheral, autonomic, and enteric 
exact mechanisms unknown
heme pathway intermediates accumulate and are neurotoxic 
Proposed Mechanisms:
heme is essential for mitochondrial electron transport used to make ATP, lack of heme may cause dysfunction in Na/K ATPase, neuronal malfunction 
Decreased production of nitric oxide by heme-containing enzyme Nitric Oxide Synthase might compromise cerebral and intestinal blood flow 

36. Exacerbating Factors:
Medications (see handout 5): most of the aggravating drugs induce hepatic ALAS1 and hepatic cytochrome P450 enzymes (CYPs).
Etomidate, ketamine, thiopental, barbituates, carbamazepine, carisoprodol, clonazepam, danazol, diclofenac, NSAIDs, estrogens, hydralazine, phenytoin, phenobarbitol, rifampin, sulfonamide antibiotics, tamoxifen, topamax, valproic acid. 
EtOH and Tobacco/Marijuana: alcohol induces ALAS1 and hepatic CYP450 enzymes 

37. Exacerbating Factors:
Sex Hormones: especially progesterone.
AIP attacks generally begin after puberty,
more common in women,
sometimes correlate with the luteal phase of menstrual cycle (when progesterone levels are highest),
progesterone is a potent inducer of hepatic ALAS1 and CYP's. 
Nutrition, glucose metabolism, and stress: starvation and/or reduced intake of calories and/or carbs,
reduced levels lead to increased ALAS1 expression. 

38. Epidemiology: 
Most common of the acute porphyrias worldwide. Prevalence 5 per 100K. (PCT is the most common overall porphyria)
Most common in Northern Europeans 
female predominance 
Age: disease of adults, typically presents in 3rd to 4th decades of life

39. Clinical Manifestations:
Abdominal Pain, most common and earliest to manifest.
severe, steady, poorly localized. Constipation, n/v, bloating, signs/symptoms of ileus, however, diarrhea can occur as well. 
Peripheral Neuropathy, sensory/motor.
pain, patchy numbness/tingling, paresthesias, motor weakness (usually proximal upper extremities), cranial nerves, bulbar paralysis, respiratory impairment. 
Autonomic, Enteric, and Central Nervous system,
tachycardia, HTN, sweating, restlessness, tremor, insomnia, anxiety, agitation, hallucinations, delirium, depression, AMS, solmnolence, coma, seizures, SIADH, Hyponatremia 
Bladder dysfunction/red urine:
dysuria, urinary retention, incontinence, darkened urine (due to accumulation of porphyrins in urine)  
No Cutaneous manifestations 
Symptoms develop over hours to days

40. Laboratory/Imaging Findings:
Hyponatremia (SIADH)
Chronically elevated transaminases; bilirubin usually normal 
mild elevation serum amylase and lipase 
abdominal imaging may show ileus 
brain imaging may show reversible densities in white matter resembling PRES:
Posterior Reversible Encephalopathy Syndrome 
Elevations of urinary porphyrin precursors (ALA and especially PBG), always present in acute attacks

41. AIP Studies (Handout 4) Urine: Plasma or Serum: Stool: RBC:
During an acute attack, AIP is characterized by elevated urinary PBG, ALA, and porphyrins (uroporphyrin and coproporphyrin)
PBG generally 20 to 200mg/day during attack (spot urine check) 
ALA markedly increased, but not to extent of PBG
Plasma or Serum: 
ALA and PBG are also elevated in plasma/serum during acute attack. 
Stool: 
normal or only slightly increased fecal porphyrin levels are seen in AIP
RBC: 
decreased erythrocyte porphobilinogen deaminase (PBGD) activity is seen in approx 90% patients. 

42. Diagnostic Evaluation: (handout 6)
Establish presence of acute porphyria and start therapy. 
stat urinary PBG level 
elevated urine PBG is sufficient to establish the presence of acute porphyria, this is the only result required to initiate treatment
(which is the same for all of the three most common acute porphyrias (AIP, HCP, VP). 
Determine the type of Acute Porphyria (AIP, HCP, VP) with biochemical testing of urine (for ALA, PBG, and porphyrins), plasma and stool (for porphyrins)
VP has elevated plasma pophyrins (AIP normal to slightly elevated)
HCP markedly elevated stool coproporphyrin III
VP markedly elevated stool coproporphyrin III and Protoporphyrin 
HCP and VP may have skin manifestations, AIP does not 
molecular testing/mutational analysis, familial testing. 

43. Management and Prognosis of AIP
Management can be challenging because the disease manifestations are diverse and potentially life threatening.
It is important to not only to treat the porphyria, but to also address any other condition
(infection, medication, etc) that my have triggered the acute attack.
Testing before therapy: testing for elevation of urinary PBG is central to the diagnosis.

44. Management and Prognosis of AIP
For patients who require further diagnostic testing to determine the type of porphyria, samples should be obtained prior to initiating therapy.
Remember (AIP, HCP, and VP) are difficult to differentiate (as stated previously)
Caveat: levels of PBG (and porphyrins and ALA) are often high in absence of symptoms, especially in those who have had prior attacks.
The elevated levels are diagnostic of an acute porphyria, but not an acute attack.
Acute attacks are based on clinical presentation and exclusion of other possible causes of the presenting signs/symptoms.

45. Therapy for an Acute Attack:
Monitor respiration, electrolytes, nutritional status, and administer glucose and IV Hemin.
Hemin or carbohydrate loading are used to abate acute attacks --> down regulate hepatic ALAS1, rate limiting step of heme biosynthesis in the liver.
Hemin is more potent and used for severe attacks,
Glucose loading is for minor attacks not requiring hospitalization
Glucose loading is also used if hemin is not available or while waiting for Hemin to arrive.
Bedside spirometry should be available in severe attacks to detect early respiratory impairment

46. Therapy for an Acute Attack:
MRI brain for evaluation of CNS symptoms, may see findings similar to PRES
Other treatments for symptomatic relief include:
opiates, antiemetics, anxiolytics, sedatives, antihypertensives, electrolyte correction.
Elimination of exacerbating factors.
Have patients keep a menstrual and attack calendar to help identify future attacks
Monitor closely for seizure like activity, however, be extremely careful as many anticonvulsant drugs exacerbate acute porphyrias.
Gabapentin and Levetiracetam are safe.

47. Hemin Dose: 3-4mg/kg IVPB single daily dose for four days.
Treatment duration may be extended if a full response is not observed within four days.
Safe during pregnancy
Hemin is a generic term used for two formuations:
Lyophilized hematin (heme hydroxide, Panhematin) is available in the USA.
Normosang (a concentrated solution of heme arginate diluted with saline) is available in Europe.

48. Hemin
Note: product labeling recommends reconstitution of Panhematin with sterile water, HOWEVER, it was discovered post-marketing that degradation products begin to form immediately upon reconstitution with sterile water, which can bind to endothelial cells and clotting factors, causing infusion site phlebitis and transient anticoagulation effect.
Thus, a widely adopted and recommended practice is to reconstitute with 25% human albumin rather than sterile water.

49. Hemin
IV administered hemin is mostly bound to albumin, and is then taken up by hepatocytes.
It enters and reconstitutes the regulatory "free" heme pool in hepatocytes and represses synthesis of the first enzyme in the heme biosynthetic pathway, ALAS1.
Repression of ALAS1 in turn decreases accumulation of heme precursors and their byproducts --> rapid and dramatic reductions in plasma and urinary PBG and ALA.

50. Hemin Side Effects: infusion site phlebitis,
Other side effects very uncommon,
fevers, mailaise, hemolysis, anaphylaxis, and circulatory collapse have been reported.
ATN is possible if excessive amounts of hematin are used.
Hemin therapy is EXPENSIVE. But it can lessen hospital length stays.
Infusion in large IV bore, PICC, or central line if available to prevent phlebitis.
Iron overload can develop after multiple hemin infusions, after doses, baseline ferritin should be collected prior to initial therapy.

51. Monitoring for complications of disease and Therapy:
- HTN
- CKD/ESRD
- HCC, age>50 years old, liver imaging, AFP
- increased iron stores. phelbotomy may be necessary.
- Liver transplant
- Genetic Counceling. (autosomal dominant, with low penetrance)

52. Overview