Differentials
CNS toxoplasmosis
SIGNS / SYMPTOMS
Exposure to cat faeces, consumption of undercooked or raw meat, focal neurological deficit, retinitis.
INVESTIGATIONS
Serum antitoxoplasma IgM and IgG: detectable with titre.
CT/MRI brain: ring-enhancing brain lesion(s), usually multiple, often involving the basal ganglia.
Non-Chagas-related cardiomyopathy
SIGNS / SYMPTOMS
Residence in Chagas non-endemic regions; history of infiltrative, storage, toxicity, endomyocardial, inflammatory, endocrine, cardiofacial, and neuromuscular/neurological causes; nutritional deficiencies; history of autoimmune or collagen diseases; history of electrolyte imbalance; history of cancer therapy.
INVESTIGATIONS
Differentiating tests vary depending on suspected underlying cause.
Toxic megacolon
SIGNS / SYMPTOMS
History of chronic use of drugs that could interfere with neuronal activity. Medication history of antacids (aluminium hydroxide and calcium carbonate), anticholinergics (pectin), antidiarrhoeals (casein), antiparkinsonians, antidepressives (tricyclics or lithium), antihypertensives or antiarrhythmics (calcium-channel blockers), metals (bismuth, iron, or heavy metals), opiates, laxatives, non-steroidal anti-inflammatory drugs, or sympathomimetics (pseudo-ephedrine).
INVESTIGATIONS
Microscopy: abnormalities vary depending on suspected underlying cause.
Non-toxic/non-Chagas megacolon
SIGNS / SYMPTOMS
History of schistosomiasis, lymphogranuloma venereum, Parkinson's disease, myotonic dystrophy, Fabry's disease (glycolipid accumulation), scleroderma, severe hypothyroidism, or amyloidosis.
INVESTIGATIONS
Microscopy: abnormalities vary depending on suspected underlying cause.
Typhoid fever
SIGNS / SYMPTOMS
High fever, rose spots (blanching erythematous maculopapular lesions), history of travel to the Indian sub-continent.
INVESTIGATIONS
Serological and microbiological examinations (blood culture, faeces culture, bone marrow culture, urine culture, skin culture): positive for Salmonella typhi.
Visceral leishmaniasis
SIGNS / SYMPTOMS
History of travel to Mediterranean basin, Middle East, central Asia, sub-Saharan Africa (in particular, East Africa), northern India, southern Nepal, or northwest Bangladesh; high exposure to sand flies; ulcerative lesions; multiple, non-ulcerative skin nodules; skin darkening.
INVESTIGATIONS
FBC: pancytopenia.
Microscopic examination of spleen aspiration, bone marrow aspirate, or lymph node fluid: amastigote form of Leishmania species in macrophages or monocytes.
Acute intestinal schistosomiasis (Katayama fever)
SIGNS / SYMPTOMS
Travel to Africa, China, the Philippines, or the Caribbean; haematuria; bloody diarrhoea; genital ulcers.
INVESTIGATIONS
Parasitological examination of the faeces: visualisation of Schistosoma species eggs.
Rectal biopsy: granulomas surrounding eggs.
Infectious mononucleosis
SIGNS / SYMPTOMS
History of sexual activity and kissing; tender lymphadenopathy; pharyngitis.
INVESTIGATIONS
Heterophile antibodies: positive.
EBV-specific antibodies: positive viral capsid antigen (VCA)-IgM, VCA-IgG, early antigen (EA), Epstein-Barr nuclear antigen (EBNA).
Congenital syphilis infection
SIGNS / SYMPTOMS
Asymptomatic (60% to 90%).
Maternal syphilis infection; low birthweight; cutaneous lesions; periostitis; osteochondritis; pseudoparalysis; phinitis; nephrotic syndrome.
INVESTIGATIONS
Serology (mother and child): VDRL and FTAs positive.
Congenital toxoplasmosis
SIGNS / SYMPTOMS
Intellectual disability; blindness; epilepsy.
INVESTIGATIONS
Serology (mother and child): high toxoplasma-specific IgM and IgG antibody titre.
Hirschsprung's disease
SIGNS / SYMPTOMS
Mainly in young children in first year of life; vomiting; explosive passage of liquid and foul stools; delayed passage of meconium; abdominal distension.
INVESTIGATIONS
Rectal biopsy: absence of ganglion cells, and presence of an excess of non-myelinated nerves.
Contrast enema: contracted distal bowel and dilated proximal bowel, with demonstration of the location of the transition zone in between.
Achalasia
SIGNS / SYMPTOMS
The most common presenting symptoms are dysphagia, regurgitation, and retrosternal pain. These can be slowly progressive over months to years.
INVESTIGATIONS
Upper gastrointestinal series shows a typical 'bird's beak' filling defect
Oesophageal manometry shows incomplete relaxation of the lower oesophageal sphincter.
Use of this content is subject to our disclaimer