The Atlas of Boricua
founder diseases
A rare diagnosis is frightening, and it often arrives with the feeling of being alone and that no one understands. This Atlas exists for the opposite: so you can see that it already has a name, already has a town, and someone already knows what it is. It is not a curse on Puerto Rico. It is why the world studies Boricua DNA, and here it is in plain language, condition by condition, with the source next to it.
What is a "founder disease"?
When a mutation enters a small group of people and that group grows more or less among itself over generations, the mutation becomes far more common there than in the rest of the world. That is the founder effect. In Puerto Rico it drew a map: certain rare diseases concentrate in specific towns. Here are the ones science has already documented.
Hermansky-Pudlak Syndrome type 1
A type of albinism with bleeding problems · HPS1 gene
Northwest (Aguadilla, Isabela, Quebradillas and nearby)
1 in 1,800 people in the northwest. 1 in 21 newborns in the northwest is a carrier.
Very fair skin and hair, vision problems, easy bruising or bleeding. In adulthood it can affect the lungs.
Source: Journal of the American Academy of Dermatology (2019); Nature Genetics
Hermansky-Pudlak Syndrome type 3
A milder form of the same albinism with bleeding · HPS3 gene
Central mountains (a genetic isolate of the island's center: Comerío, Naranjito, Barranquitas)
1 in 32 newborns in the island's center is a carrier.
Similar to type 1 but usually milder.
TBCK Syndrome ("Boricua Syndrome")
A childhood neurogenetic disease · TBCK gene, p.R126X variant
Islandwide; the founder variant was identified in Puerto Rico
About 21 families identified in PR, out of some 100 cases worldwide.
Baby with very low muscle tone ("floppy"), epilepsy, developmental delay, trouble speaking and swallowing.
Primary Ciliary Dyskinesia (RSPH4A variant)
A chronic respiratory disease from birth · RSPH4A gene, c.921+3_6delAAGT variant
Most common in the west. Mayagüez holds about 30% of cases.
The Boricua variant explains 2 of every 3 cases of this disease in PR. An estimated 1,624 people affected.
Congestion, ear infections and sinusitis from infancy, chronic cough. Mistaken for asthma or allergies for years.
Limb-Girdle Muscular Dystrophy type 2C
A slowly progressing muscle weakness · SGCG gene, p.E263K variant
Documented as a founder variant in the Puerto Rican population
Founder variant in Puerto Rican Hispanics. One of the conditions the news describes as "similar to muscular dystrophy".
Slowly advancing weakness in hips and shoulders: hard to run, climb stairs, or get up from the floor.
Source: PMC / NIH (2015): forma lentamente progresiva de LGMD2C por variante fundadora en SGCG
Hereditary Breast and Ovarian Cancer (BRCA2 E1308X)
An inherited genetic cancer risk that runs in families · BRCA2 gene, E1308X variant
Islandwide; explains most hereditary cases in PR
A single founder variant explains most hereditary breast and ovarian cancer in Puerto Rico.
Several breast or ovarian cancer cases in the same family, or at a young age. This one CAN be acted on: there are genetic tests and prevention.
Warning signs from infancy
Early detection is what shortens the odyssey. If a baby or child shows several of these signs, it is not to panic, it is to ask early:
- Delay reaching milestones (sitting, walking, talking)
- Trouble feeding or swallowing
- Seizures or involuntary movements
- Poor growth or unexpected weight loss
- Frequent or severe infections
- Several similar cases in the family
No single sign means a rare disease. But if several come together, mentioning it to the pediatrician early can save years. Source: El Vocero (2026), Office for Rare Diseases.
If any of this sounds like your family
You do not have to solve it today or understand everything. One concrete first step: see who can diagnose and where the nearest one is to you.
Citable data
Each fact with its source and something to do. When you copy, it carries the page link: a message to the family, a press note, a question for the doctor.
📤 Pásalo a quien le toca
To anyone with a rare case in the family, a pediatrician, a teacher. It can save someone years of not knowing.
One important thing, neighbor to neighbor
This is not a substitute for medical advice. We verify public data, but phone numbers, health plans, and availability change. Before you go, call and confirm.
Spotted outdated info? Tell us and we fix it: angel@angelanderson.com