Volume 4 Issue 6 June, 2014
Consultation Liaison Psychiatry Focus: ‘Microbiology’
PANDAS, is an abbreviation for Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal
Infections.
The children usually have dramatic, “overnight” onset of symptoms, including motor or vocal tics, obsessions, and/or
compulsions. In addition to these symptoms, children may also become moody, irritable or show concerns about
separating from parents or loved ones. This abrupt onset is generally preceded by a Streptococcus throat infection.
The PANDAS hypothesis was based on observations in clinical case studies at the US National Institute of Health and in
subsequent clinical trials where children appeared to have dramatic and sudden OCD exacerbations and tic disorders
following infections. There is supportive evidence for the link between streptococcus infection and onset in some cases
of OCD and tics, but proof of causality has remained elusive. The PANDAS hypothesis is controversial; whether it is a
distinct entity differing from other cases of Tourette syndrome (TS)/OCD is debated.
The causative organism Group A β Hemolytic Streptococcus is a spherical, Gram-positive, non-motile organism and the
most common bacterial cause of acute pharyngitis (“strep throat”) in children and young adults. The diseases caused by Streptococcus can be (1) Suppurative or (2) Non-suppurative – which includes the sequelae to post-streptococcal
infections. Numerous serotypes of Group A β Hemolytic Streptococcus have varying degrees of disease activity with
classification based on antigenic surface proteins M and T. Its armament of antigenic surface proteins and pyrogenic
exotoxins, as well as its ability to lyse its way systemically and evade the immune system effectively, have been well
characterized. M protein, for example, is the major virulence factor preventing phagocytosis, multiplying rapidly in
human tissue and initiating the disease process.
What is the mechanism behind this phenomenon?
At present, it is unknown but researchers are pursuing a theory that the mechanism is similar to that of Rheumatic
Fever, an autoimmune disorder triggered by strep throat infections. The phenomenon is called “molecular mimicry“. In
PANDAS Basal Ganglia gets affected, which is believed to be responsible for disorders of movement and behavior.
The anti-streptococcal antibody titer determines whether there is immunologic evidence of a previous strep infection.
Two different strep tests are commercially available: the antistrepolysin O (ASO) titer, which rises 3-6 weeks after a strep infection, and the antistreptococcal DNAase B (AntiDNAse-B) titer, which rises 6-8 weeks after a strep infection. An elevated anti-strep titer (such as ASO or AntiDNAse-B) means the child has had a strep infection sometime within the past few months, and his body created antibodies to fight the strep bacteria. However throat culture may be considered as gold standard for diagnosis. Since it is a post suppurative infection the presence of causative factor in the throat for culture and sensitivity is questionable.
Treatment: Role of Antibiotics for treatment is still questionable. Drugs such as penicillin group can be used. But with
present scenario of Drug resistance, many Streptococcal groups may not respond to long term use of Penicillin group of drugs.
