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Key Facts: ABMGG Medical Biochemical Genetics Exam

100

Subspecialty Exam Items

ABMGG Testing Process page

2 hrs

Total Exam Time

ABMGG 2026 Bulletin

$1,775

Total First-Time Cost

ABMGG 2026 Bulletin (review + subspecialty)

12 mo

Required Fellowship

ACGME Medical Biochemical Genetics Program Requirements

Aug 12-15

2026 Exam Dates

ABMGG Dates & Fees page

6 years

Board Eligibility Window

ABMGG Board Eligibility Policy

ABMGG offers Medical Biochemical Genetics as a 1-year fellowship subspecialty for board-certified clinical geneticists who manage IEM patients clinically. The exam runs 100 multiple-choice items in two 60-minute blocks at Pearson VUE, August 12-15, 2026. The 2026 fee is $1,000 subspecialty + $775 application review = $1,775. Prerequisites: ABMGG Clinical Genetics & Genomics certification plus 12 months of ACGME-accredited Medical Biochemical Genetics fellowship completed by July 31, 2026.

Sample ABMGG Medical Biochemical Genetics Practice Questions

Try these sample questions to review concepts for the ABMGG Medical Biochemical Genetics exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1A 2-week-old infant is identified by newborn screening with a phenylalanine level of 1,200 umol/L (normal <120). What is the appropriate initial dietary intervention?

A.Phenylalanine-restricted formula with Phe-free medical food supplementation

B.Total protein restriction to less than 0.5 g/kg/day

C.Switch to a soy-based standard infant formula

D.Initiate parenteral nutrition with branched-chain amino acid restriction

Explanation: Classical PKU is managed by combining a measured amount of standard infant formula or breast milk (to provide the minimum required Phe) with a Phe-free medical food to supply remaining protein, energy, vitamins, and minerals. Goal blood Phe is 120-360 umol/L. Total protein restriction would cause catabolism. Soy formula still contains Phe.

2A 14-year-old with PKU has struggled with diet adherence. Genetic testing shows two missense PAH variants with predicted residual enzyme activity. Which adjunctive therapy may allow liberalization of his diet?

A.Sapropterin dihydrochloride (BH4)

B.Nitisinone (NTBC)

C.Sodium phenylbutyrate

D.Carglumic acid

Explanation: Sapropterin (Kuvan) is a synthetic BH4 cofactor that can lower blood phenylalanine in approximately 25-50% of PKU patients with residual PAH activity (typically missense variants). Responders may tolerate increased dietary Phe. Nitisinone is for tyrosinemia type I, sodium phenylbutyrate is for urea cycle disorders, and carglumic acid is an NAGS analog.

3A 28-year-old woman with classical PKU desires liberation from her low-Phe diet. Which therapy is FDA-approved for adults with PKU and uses an enzyme substitution mechanism?

A.Pegvaliase (Palynziq)

B.Sapropterin

C.Tetrahydrobiopterin

D.Glycerol phenylbutyrate

Explanation: Pegvaliase is a PEGylated recombinant phenylalanine ammonia lyase (PAL) approved for adults with PKU and uncontrolled blood Phe (>600 umol/L). It substitutes for absent PAH activity by converting Phe to ammonia and trans-cinnamic acid. Risk of anaphylaxis requires REMS enrollment.

4A woman with PKU is planning pregnancy. What target blood phenylalanine level should be achieved BEFORE conception and maintained throughout pregnancy to prevent maternal PKU syndrome in the fetus?

A.120-360 umol/L

B.360-600 umol/L

C.600-900 umol/L

D.Less than 50 umol/L

Explanation: Maternal PKU syndrome (microcephaly, congenital heart disease, intellectual disability, IUGR) is prevented by maintaining maternal Phe between 120-360 umol/L from preconception through delivery. Phe levels >360 umol/L during pregnancy are teratogenic regardless of fetal genotype.

5A 5-day-old infant presents with poor feeding, lethargy, and a sweet maple syrup odor in the urine. Newborn screening showed elevated leucine. Which biochemical findings confirm the diagnosis?

A.Elevated leucine, isoleucine, valine, and presence of alloisoleucine

B.Elevated phenylalanine with reduced tyrosine

C.Elevated methylmalonic acid in urine

D.Elevated propionylcarnitine (C3) on acylcarnitine profile

Explanation: Maple syrup urine disease is caused by branched-chain alpha-ketoacid dehydrogenase (BCKDH) deficiency. Diagnosis requires elevated branched-chain amino acids (leucine, isoleucine, valine) plus alloisoleucine, which is pathognomonic. Untreated patients develop cerebral edema.

6A 3-year-old with classical MSUD presents with vomiting, ataxia, and a leucine of 2,000 umol/L. After starting BCAA-free formula and IV dextrose/insulin, leucine remains elevated at 1,800 umol/L 12 hours later. What is the next best step?

A.Initiate hemodialysis or CRRT

B.Increase IV protein with standard amino acid solution

C.Administer high-dose thiamine 100 mg IV

D.Begin nitisinone therapy

Explanation: Severe MSUD decompensation with leucine >1,500 umol/L unresponsive to anabolic measures requires extracorporeal removal. Hemodialysis or CRRT can reduce leucine by 70% in hours. Standard amino acids contain BCAAs. Thiamine helps in thiamine-responsive MSUD but won't acutely reduce leucine. Nitisinone is for tyrosinemia.

7A 6-month-old with hepatomegaly, coagulopathy, and renal Fanconi syndrome has elevated succinylacetone in urine. What is the standard pharmacologic therapy?

A.Nitisinone (NTBC) plus low-tyrosine, low-phenylalanine diet

B.Liver transplantation as first-line therapy

C.N-acetylcysteine and vitamin E

D.Sodium benzoate and L-arginine

Explanation: Tyrosinemia type I (FAH deficiency) is treated with nitisinone, which inhibits 4-hydroxyphenylpyruvate dioxygenase upstream, preventing accumulation of toxic fumarylacetoacetate and succinylacetone. Combined with dietary restriction of tyrosine and phenylalanine, it has dramatically reduced the need for liver transplant.

8A 12-year-old with marfanoid habitus, downward lens dislocation, intellectual disability, and a history of DVT has elevated total plasma homocysteine. Which enzyme defect is most likely?

A.Cystathionine beta-synthase (CBS) deficiency

B.Methylenetetrahydrofolate reductase (MTHFR) deficiency

C.Methionine synthase deficiency

D.Cobalamin C (cblC) defect

Explanation: Classical homocystinuria from CBS deficiency presents with marfanoid habitus, ECTOPIA LENTIS (downward, distinguishing from Marfan's upward lens dislocation), thromboembolism, and intellectual disability. Plasma methionine is HIGH (vs low/normal in remethylation defects like MTHFR or cblC). Treatment includes pyridoxine, methionine restriction, betaine.

9A previously healthy 18-month-old boy presents with vomiting, lethargy, and ammonia of 600 umol/L. Plasma amino acids show low citrulline and elevated glutamine. Urine orotic acid is markedly elevated. What is the diagnosis?

A.Ornithine transcarbamylase (OTC) deficiency

B.Carbamoyl phosphate synthetase 1 (CPS1) deficiency

C.Argininosuccinate synthetase (citrullinemia type I)

D.N-acetylglutamate synthase (NAGS) deficiency

Explanation: OTC deficiency (X-linked) presents with hyperammonemia, low citrulline (proximal block), and elevated urinary orotic acid (carbamoyl phosphate diverts to pyrimidine synthesis). CPS1 and NAGS deficiencies have low citrulline but NORMAL/LOW orotic acid. Citrullinemia I has HIGH citrulline.

10A neonate with newly diagnosed urea cycle disorder has an ammonia of 750 umol/L. After initiating IV sodium phenylacetate/benzoate (Ammonul) and L-arginine, what is the most appropriate next step?

A.Initiate hemodialysis

B.Continue scavenger therapy and recheck ammonia in 6 hours

C.Administer sodium bicarbonate IV push

D.Start enteral protein at 1 g/kg/day

Explanation: Neonatal hyperammonemia >500 umol/L (or any ammonia not responding rapidly to scavengers, or >300 with neurologic symptoms) requires immediate hemodialysis. CRRT is acceptable but conventional hemodialysis clears ammonia faster. Delays cause irreversible brain injury. Protein must be HELD initially, not advanced.

About the ABMGG Medical Biochemical Genetics Exam

The ABMGG Medical Biochemical Genetics subspecialty exam certifies physicians who provide clinical management for patients with inborn errors of metabolism (IEM). The 100-item, 2-hour exam covers diagnosis, dietary therapy, pharmacologic management, acute decompensation care, and emerging therapies (ERT, substrate reduction, gene therapy). Distinct from the Clinical Biochemical Genetics (laboratory-directing) track, this credential focuses on direct patient care across aminoacidopathies, organic acidemias, FAO defects, lysosomal and mitochondrial disorders, and newborn screening follow-up.

Exam sponsor: ABMGG / Pearson VUE. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Questions

100 questions

Time Limit

2 hours

Passing Score

Criterion-referenced (content-expert standard)

Exam / Certification Fees

$1,775 (subspecialty exam $1,000 + application review $775)

Exam sponsor website

Reported exam pass rate: Not publicly released. ABMGG does not publish pass rates by subspecialty Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Official sources

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

20%

Aminoacidopathies & Urea Cycle Disorders

PKU, MSUD, tyrosinemia, homocystinuria, urea cycle defects (OTC, CPS1, ASS, ASL, ARG1), nitrogen scavenger therapy, and protein-restricted diets

15%

Organic Acidemias

Methylmalonic acidemia, propionic acidemia, isovaleric acidemia, glutaric aciduria type 1, cobalamin disorders, and acute metabolic decompensation management

12%

Fatty Acid Oxidation Defects

MCAD, VLCAD, LCHAD, CPT1/CPT2, carnitine transport defects, hypoglycemia management, and dietary fat modification (MCT oil, triheptanoin)

12%

Lysosomal Storage Disorders

Gaucher, Fabry, Pompe, MPS I-VII, Niemann-Pick, Krabbe, MLD, enzyme replacement therapy, substrate reduction therapy, and HSCT indications

10%

Carbohydrate & Glycogen Storage Disorders

Galactosemia, hereditary fructose intolerance, GSD I-IX, congenital disorders of glycosylation (CDG), and dietary carbohydrate management

10%

Mitochondrial Disorders

MELAS, MERRF, Leigh syndrome, Kearns-Sayre, mtDNA depletion syndromes, heteroplasmy interpretation, and supportive cofactor therapy

Newborn Screening & Diagnosis

RUSP panel, MS/MS interpretation, confirmatory testing algorithms, false positives/negatives, and ACMG ACT sheets

Acute Metabolic Decompensation

Hyperammonemia protocols, hemodialysis indications, glucose/insulin infusion, anabolic state induction, and emergency letters

Peroxisomal & Other Disorders

Zellweger spectrum, X-ALD, Refsum disease, very long chain fatty acid testing, and bile acid synthesis defects

Novel & Emerging Therapies

Gene therapy (Zolgensma, Elevidys), mRNA therapy, antisense oligonucleotides, pharmacological chaperones, and clinical trial considerations

Preparing for the ABMGG Medical Biochemical Genetics Exam

What You Need to Know

Passing score: Criterion-referenced (content-expert standard)
Exam length: 100 questions
Time limit: 2 hours
Exam / certification fees: $1,775 (subspecialty exam $1,000 + application review $775) Official sources

Using Our Practice Resources

Work through all 100 available questions
Review every answer and explanation
Track weak areas and revisit them
Use our AI tutor for tough concepts

ABMGG Medical Biochemical Genetics: Suggested Study Strategy

1Memorize the urea cycle and the differential for hyperammonemia: OTC (X-linked, low citrulline, high orotic acid) vs CPS1/NAGS (low citrulline, normal orotic) vs ASS/ASL (high citrulline)

2Build acute decompensation protocols cold: stop protein, give D10 + insulin to drive anabolism, IV ammonia scavengers (sodium phenylacetate/benzoate), L-arginine, and hemodialysis if ammonia >500 umol/L

3Master MS/MS newborn screening signatures: C3 (PA/MMA), C4 (IVA/SCAD), C5-OH (3-MCC/HMG), C5DC (GA1), C8 (MCAD), C14:1 (VLCAD), C16+C18:1 (CPT2/LCHAD)

4Know FDA-approved enzyme replacement therapies: imiglucerase/velaglucerase (Gaucher), agalsidase/pegunigalsidase (Fabry), alglucosidase/avalglucosidase (Pompe), laronidase (MPS I), idursulfase (MPS II)

5Learn dietary management essentials: low-Phe diet (PKU), branched-chain restriction (MSUD), low-protein + carnitine + B12 (MMA/PA), avoid fasting + low LCT/high MCT (LCHAD/VLCAD), galactose-free formula (galactosemia)

6Review novel therapies: nitisinone (tyrosinemia type I), sapropterin (BH4-responsive PKU), pegvaliase (PKU), migalastat chaperone (Fabry), Zolgensma gene therapy (SMA), Elevidys (DMD)

Frequently Asked Questions

How many questions are on the ABMGG Medical Biochemical Genetics exam?

The ABMGG Medical Biochemical Genetics subspecialty exam has 100 multiple-choice items administered in two 60-minute testing blocks of 50 items each, totaling 2 hours of testing time at Pearson VUE centers.

What is the difference between Medical Biochemical Genetics and Clinical Biochemical Genetics?

Medical Biochemical Genetics certifies physicians for clinical management of inborn errors of metabolism (direct patient care, dietary therapy, ERT). Clinical Biochemical Genetics certifies laboratory directors who interpret biochemical tests. They are distinct ABMGG credentials with separate exams.

What are the prerequisites for the ABMGG Medical Biochemical Genetics exam?

Candidates must hold ABMGG Clinical Genetics and Genomics certification (or be board-eligible) and complete a 12-month ACGME-accredited Medical Biochemical Genetics fellowship by July 31, 2026, plus hold a valid unrestricted medical license.

How much does the ABMGG Medical Biochemical Genetics exam cost in 2026?

The 2026 fee is $1,000 for the subspecialty exam plus a $775 application review fee, totaling $1,775 for first-time candidates. A $400 late fee applies after the January 15 deadline. Re-examinees pay a $525 application review fee.

When is the 2026 ABMGG Medical Biochemical Genetics exam offered?

The 2026 ABMGG subspecialty exams, including Medical Biochemical Genetics, are offered August 12-15, 2026, at Pearson VUE test centers worldwide. Candidates schedule a single 2-hour appointment within this window.

What topics are most heavily weighted on the exam?

The largest blueprint domains are aminoacidopathies and urea cycle disorders (20%), organic acidemias (15%), fatty acid oxidation defects (12%), and lysosomal storage disorders (12%). Together these account for nearly 60% of the exam.