SNP Shot: Genomic Insights

Juvenile polyposis syndrome (JPS) is a condition where multiple non-cancerous growths, known as juvenile polyps, develop in the gastrointestinal (GI) tract. While the name includes "juvenile," it refers to the tissue type of the polyps, not necessarily the age of onset. People with JPS usually develop polyps before age 20. These polyps commonly occur in the large intestine (colon), but can be found throughout the GI tract. The number of polyps can vary greatly, even within the same family, ranging from a few to hundreds. These polyps can cause symptoms like gastrointestinal bleeding, anemia (low red blood cell count), abdominal pain, and diarrhea. About 15% of individuals with JPS also have other abnormalities, such as intestinal malrotation, heart or brain defects, cleft palate, extra digits (polydactyly), or genital and urinary tract abnormalities.

A diagnosis of juvenile polyposis syndrome is made when a person has one or more of the following: more than five juvenile polyps in the colon or rectum; juvenile polyps in other parts of the GI tract; or any number of juvenile polyps along with a family history of the condition. The presence of a single juvenile polyp is common in children and does not typically indicate JPS.

There are three recognized types of JPS, categorized by the symptoms and polyp location. Juvenile polyposis of infancy involves polyps throughout the GI tract during infancy. This is the most severe form and has the poorest prognosis. Children with this type may develop protein-losing enteropathy, leading to severe diarrhea, failure to thrive, and cachexia (wasting). Generalized juvenile polyposis is characterized by polyps throughout the GI tract, while juvenile polyposis coli involves polyps exclusively in the colon. Both generalized juvenile polyposis and juvenile polyposis coli usually present during childhood.

Although most juvenile polyps are benign, there is a risk of them becoming cancerous (malignant). People with JPS have an estimated 10-50% lifetime risk of developing cancer in the gastrointestinal tract, with colorectal cancer being the most common type.

Inheritance:

JPS follows an autosomal dominant inheritance pattern. This means that only one copy of the mutated gene is needed in each cell to cause the condition. About 75% of affected individuals inherit the mutated gene from a parent who also has JPS. In the remaining 25% of cases, the mutation occurs spontaneously (de novo) and the person has no family history of the disorder.