Clinico-Epidemiological study of Polymorphic Light Eruption and Biochemical Correlation of Thyroid Dysfunction among these patients: A case-control study

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Background: The most common idiopathic photodermatosis is Polymorphic light eruption (PMLE), which is manifested by dermal abnormalities, particularly itching on areas exposed to the sun. Chronic skin diseases like PMLE are believed to be closely linked to endocrine disorders, especially autoimmune thyroid disorders. Despite all the associations, very little Indian literature prevails regarding PMLE and thyroid dysfunction. Objectives: To analyze the risk factors associated with PMLE and to evaluate the prevalence of thyroid dysfunction among PMLE patients and healthy controls. Materials and Methods: This study was carried out in the department of Dermatology of Chettinad Hospital and Research Institute (CHRI), over 3 months from August 2025 to September 2025. A total of 64 PMLE patients and 64 healthy controls were recruited for the study after getting ethical committee approval (IHEC-I/4169/25). Physical examination and thyroid function tests (Serum T3, T4 and TSH), using chemiluminescent immunoassay, were conducted. Data were analysed using SPSS software v.25. T-test and chi-square tests were done, with pvalue <0.05 considered statistically significant. Results: Serum total T3 and T4 values were lower in cases (p=0.002 & p=0.01), but the mean TSH value was higher in cases than in controls, with statistical significance (p < 0.001). Thyroid disorders were found in 28.1% of PMLE cases and in 9.4% of healthy controls, with statistical significance (p=0.009), and it also shows a positive association with family history of thyroid disorders (p=0.02). Conclusion: The association of PMLE and hypothyroidism establishes a strong link between autoimmune and endocrine disorders. Combining screening of thyroid disorders in PMLE assessment may help in prompt diagnosis and thus early treatment measures.