Strep throat (Streptococcal pharyngitis) is a common bacterial infection of the throat and tonsils, caused by Group A Streptococcus (GAS) bacteria (Streptococcus pyogenes). While acute symptoms like sore throat and fever are uncomfortable, the primary concern is the potential for serious, long-term complications. Untreated strep throat can lead to issues affecting the heart, kidneys, and brain weeks later. Seeking diagnosis and appropriate treatment is necessary to prevent these severe health consequences.
Acute Illness Progression and Transmission Risk
If antibiotics are not administered, acute symptoms may persist for up to two or three weeks. The patient remains infectious for an extended period, posing a public health risk. Group A Streptococcus bacteria are highly contagious and spread easily through respiratory droplets from coughing or sneezing. Untreated individuals can spread the infection for weeks until the body naturally clears the bacteria. In contrast, a person starting antibiotics becomes non-contagious quickly, usually after just 24 hours of treatment. Prompt antibiotic use shortens the illness and reduces the risk of spreading the infection.
The Danger of Rheumatic Fever
Acute rheumatic fever (ARF) is the most severe complication of untreated strep throat, typically appearing two to four weeks after the initial infection. ARF is a serious immune-mediated response where the body’s defenses mistakenly attack its own tissues. The immune system generates antibodies against the GAS bacteria, but because bacterial proteins closely resemble certain human proteins, the antibodies begin attacking healthy cells. This misdirected attack causes widespread inflammation affecting multiple organ systems throughout the body.
The heart is particularly susceptible, resulting in carditis, which can lead to permanent damage of the heart valves, known as rheumatic heart disease (RHD). RHD often requires lifelong medical management and, in severe cases, heart valve replacement surgery.
The inflammatory process also targets the joints, causing arthritis characterized by painful, swollen, and tender joints that often migrate between the ankles, knees, and wrists. Additionally, the central nervous system can be affected, leading to Sydenham chorea. This temporary neurological disorder manifests as involuntary, jerky, and uncontrollable movements of the face, hands, and feet, sometimes accompanied by sudden emotional outbursts. Preventing this complex chain of events is the primary goal of antibiotic treatment.
Kidney Damage from Post-Streptococcal Glomerulonephritis
Post-streptococcal glomerulonephritis (PSGN) targets the kidneys and is an immune-mediated reaction. It occurs when immune complexes (antibodies and bacterial antigens) deposit in the kidney’s filtering units, the glomeruli, triggering inflammation and damage.
Symptoms of PSGN typically appear about ten days after infection and relate to impaired kidney function. Patients may notice dark, reddish-brown urine, indicating the presence of blood. Swelling (edema) is common around the eyes, hands, and feet due to the kidneys’ reduced ability to remove excess fluid and salt. The resulting fluid imbalance can also lead to hypertension (high blood pressure).
While most patients, especially children, recover fully from PSGN within a few weeks, the condition can, in rare circumstances, progress to chronic kidney disease. This risk emphasizes the need for early diagnosis and treatment of the initial strep infection to prevent kidney inflammation.
Potential Neurological and Autoimmune Issues
Untreated Group A Streptococcus infection has been implicated in certain neurological and psychiatric disorders. One condition, still a subject of ongoing research, is Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS). This syndrome is characterized by the sudden, dramatic onset or exacerbation of neurological or psychiatric symptoms in children following a strep infection.
The mechanism involves molecular mimicry, similar to rheumatic fever, where antibodies against the bacteria mistakenly cross-react with cells in the basal ganglia, the brain region controlling movement and behavior. This autoimmune attack can result in the rapid development of severe obsessive-compulsive disorder (OCD) or tic disorders. Other symptoms include sudden anxiety, mood swings, and loss of fine motor skills. The sudden onset distinguishes PANDAS from gradual-onset mental health conditions.