Photo Credit: Md Saiful Islam Khan

The following is a summary of “Seasonal distribution of immune thrombotic thrombocytopenic purpura is influenced by geography: Epidemiologic findings from a multi-center analysis of 719 disease episodes,” published in the August 2024 issue of Hematology by Jacobs et al.  

Previous studies have suggested that immune thrombotic thrombocytopenic purpura (iTTP) might show seasonal variation. However, limitations in methodology and small sample sizes have made it challenging to conduct a thorough assessment of this pattern.  

Researchers conducted a retrospective study exploring the epidemiology of iTTP to determine if it exhibits a seasonal pattern.   

They included patients with both initial and relapsed iTTP (defined as a disintegrin and metalloprotease with thrombospondin type motifs 13 activity <10%) from 24 tertiary centers across Australia, Canada, France, Greece, Italy, Spain, and the US. Seasons were categorized as follows: Northern Hemisphere – Winter (December–February); Spring (March-May); Summer (June–August); Autumn (September-November) and Southern Hemisphere – Winter (June-August); Spring (September–November); Summer (December–February); Autumn (March-May). The study also looked at mean temperature during months with and without an iTTP episode at each site.   

The results showed that a total of 583 patients experienced 719 iTTP episodes. The observed proportion of iTTP episodes during winter was significantly higher than expected if they were evenly distributed across the seasons, with 28.5% (205/719) during winter (25.3%-31.9%; P=0.03). Additionally, distance from the equator and mean temperature deviation both positively correlated with the proportion of iTTP episodes in winter. Acute iTTP episodes were linked to the winter season and colder temperatures, with a second peak occurring during summer. The occurrence of episodes in winter was most noticeable at sites farther from the equator and/or with greater annual temperature deviations.   

Investigators concluded the reasons behind the seasonal patterns of this disease could help in discovering and developing future preventive therapies and aid in planning for resource utilization.   

Source: onlinelibrary.wiley.com/doi/10.1002/ajh.27458