Hunter syndrome is the X-linked mucopolysaccharidosis: iduronate-2-sulfatase deficiency causes heparan and dermatan sulfate storage, coarse facies, hepatosplenomegaly, recurrent infections, and clear corneas.
The anchor: When the stem says coarse facies plus GAG storage, first split Hunter from Hurler: Hunter is X-linked and has no corneal clouding.
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Pedigree Detective
A 6-year-old boy with coarse facies, hepatosplenomegaly, joint stiffness, and developmental regression. Tap each family member to mark who's affected. The pedigree pattern unmasks the inheritance · the inheritance unmasks the disease.
Unaffected Affected□ Male○ Female
Step 1. Tap the patient (III-2) and his brother (III-3) to mark them affected.
From the Attending
Only boys affected, skipped generations, carried by an asymptomatic mother = X-linked recessive. The MPS that fits that pattern is Hunter syndrome (iduronate-2-sulfatase). Hurler is autosomal recessive · the inheritance is the entire splitter. No corneal clouding in Hunter is the second tiebreaker.
THE VISUAL ANCHOR
The Hunter Split
The disease looks like an MPS. The scoring move is the split: Hunter is X-linked and has no corneal clouding.
The GAG Traffic Jam
Boy + PedigreeAffected males and carrier females point to X-linked recessive disease.
Other LSDsTay-Sachs, Krabbe, and Niemann-Pick are sphingolipid lanes.
From the Attending
Hunter syndrome (MPS II) is the X-linked recessive sister of Hurler (MPS I, autosomal recessive, more severe). Both pile up heparan + dermatan sulfate, but the giveaway is the eyes: Hurler clouds the cornea, Hunter does NOT. Boy with coarse facies, HSM, joint stiffness, recurrent ear infections, developmental delay, and clear corneas = Hunter. Add corneal clouding to the same picture and you flip to Hurler. Enzyme = iduronate-2-sulfatase. "Hunter sees clearly" is the only mnemonic you need.
INTERACTIVE
Sort Hunter From The Storage Decoys
Place each clue into the Hunter bucket or into the wrong lysosomal storage lane.
Pick a chip, then place it in the correct bucket.
Hunter MPS II
Decoy Storage Disease
From the Attending
Lysosomal storage diseases follow one logic: enzyme broken → substrate stuck → organ overloaded. Match the substrate to the disease: Heparan + Dermatan sulfate → Hurler/Hunter (MPS). Glucocerebroside → Gaucher (crumpled-tissue-paper macrophages). Sphingomyelin → Niemann-Pick (cherry-red macula, foam cells). GM2 ganglioside → Tay-Sachs (cherry-red macula, NO HSM). Galactocerebroside → Krabbe (globoid cells). The substrate names the disease; the cherry-red macula splits Tay-Sachs from Niemann-Pick on HSM.
BATTLE MAP
Hunter Versus Hurler
Same stored GAGs, different enzyme, different inheritance, different cornea.
Memory Hooks
Hunter is the HUNTER without hazy corneas.
Hunter and Fabry are the X-linked lysosomal storage exceptions.
Hunter and Hurler store the same GAGs; enzyme, eye, and inheritance separate them.
ELIMINATION GAME
Eliminate The Decoys
Use the full clue stack instead of matching one vague storage-disease phrase.
Eliminate the distractors until the board move is the only one standing.
Hunter syndrome
MPS II, X-linked
Hurler syndrome
Corneal clouding
Tay-Sachs disease
GM2, no HSM
Krabbe disease
Globoid cells
Niemann-Pick disease
Foam cells
BOARD-STYLE WALKTHROUGH
Clinical Vignettes
25 original clinical cases. Answers shuffle each round. Front-side exam tools work before reveal.
From the Attending
Hunter vignette tells: (1) Boy (X-linked) with (2) coarse facies + HSM + joint stiffness + recurrent ear infections and (3) CLEAR corneas. Labs: elevated urinary heparan + dermatan sulfate · confirm with low iduronate-2-sulfatase enzyme activity in leukocytes/fibroblasts. Treatment: idursulfase (recombinant enzyme replacement). Doesn't cross BBB · CNS disease still progresses. If a girl presents with the same picture, you're looking at autosomal recessive Hurler (MPS I), not Hunter · and her corneas will cloud.
