Prognosis

The prognosis varies greatly depending on the immune status of the host. In immunocompetent patients without other complications (e.g., malnutrition), cryptosporidiosis is self-limiting and a full recovery is expected. In immunocompromised patients the prognosis is determined by the nature of the underlying condition.

Immunocompetent patients

Disease is self-limited in immunocompetent patients; symptoms usually resolve in 7 to 14 days, although may last 3 to 4 weeks (mean 13 days, median 11 days).[38] Initial improvement is followed by brief recurrence of symptoms in about one third of cases after a median of 3 days (range 2 to 10 days).[73] Within 3 months of initial infection, 40% of patients have reported recurrence of gastrointestinal symptoms after recovery from initial infection.[106]

Seronegative reactive arthritis has been reported in adults​​ and children,​​ including one report of reactive arthritis (arthritis, conjunctivitis, and urethritis).[107][108]​​​​​[109][110]​​​​ Reported joint pain was of longer duration in patients with cryptosporidiosis than in healthy controls in a UK study conducted 2 months after initial diagnosis of Cryptosporidium infection.[106] Joint pain, eye pain, recurrent headache, dizzy spells, and fatigue were significantly more common in C. hominis but not C. parvum cases than in well controls.[106] Patients should be advised that symptoms of postinfective irritable bowel syndrome have been described in up to 14% of cases in the first year after cryptosporidiosis.[111][112]​​ One systematic review of case-control studies also found chronic diarrhea six times more likely ​and weight loss three times more likely, up to 28 months after acute cryptosporidiosis, than in controls. Other symptoms (long-term abdominal pain, loss of appetite, fatigue, vomiting, joint pain, headache and eye pain) were two to three times more likely following a Cryptosporidium infection.[113] A significant association between colorectal cancer and Cryptosporidium has been reported and plausible potential mechanisms for cell transformation and Cryptosporidium-induced cancer described, but not evidence for causation.[114]​​[115]

Infection confers a degree of immunity, but recurrent infections are possible.

Immunocompromised patients

Disease may be prolonged and refractory to treatment. Antimicrobial therapy may ameliorate symptoms but is seldom curative, with relapse often occurring when treatment is discontinued. Usually only improvement in the underlying immune condition results in significant improvement. Relapses can also occur following deterioration in immune function, if infection has been suppressed but not completely cleared.

Patients with HIV with CD4+ counts >180/mm^3 are more likely to have transient or self-limited disease.[75][76] Fulminant disease (marked by the passing of >2 liters stool per day) has only occurred in patients with CD4+ counts <50/mm^3.[76] Lower CD4+ counts were predictive of chronic diarrhea.[77] Four distinct clinical syndromes of cryptosporidiosis have been identified in patients with AIDS with CD4+ counts <200/mm^3: transient diarrhea, relapsing illness, chronic diarrhea, and cholera-like illness.[11] In this patient group, chronic diarrhea and cholera-like illness with severe weight loss predominated. Although cryptosporidiosis significantly influenced survival rates, this was not linked to individual cryptosporidiosis clinical syndromes.[11]

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