Relevance. Magnesium is a vital cation that serves as a cofactor in numerous biochemical reactions within the human body. It plays a crucial role in various intracellular processes, including calcium homeostasis, signal transduction, and energy metabolism regulation. Deficiency of this essential micronutrient can manifest early in life and may result in a range of pathological conditions, some of which pose a significant threat to a child's health.

Description of the clinical case. The parents of an 18-month-old child presented to the clinic at Kuban State Medical University, under the Ministry of Health of the Russian Federation, with concerns regarding gingival overgrowth. The child’s medical history revealed seizure episodes of unknown origin that had first occurred at three months of age, necessitating the administration of multiple high-dose anticonvulsant medications. Upon examination, edema of the subcutaneous tissue in the face, trunk, and limbs was noted, along with pronounced gingival hypertrophy in the absence of inflammatory signs. A provisional diagnosis of drug-induced gingival fibromatosis was established. To clarify the diagnosis and optimize anticonvulsant therapy, molecular genetic testing was recommended. The results confirmed autosomal recessive hypomagnesemia with secondary hypocalcemia, attributed to previously unreported genetic mutations. Inpatient treatment included magnesium supplementation with the gradual tapering of anticonvulsant medications. Over the course of treatment, a marked reduction in gingival hypertrophy was observed, and no further seizure episodes occurred.

Conclusion. The diagnosis of genetically determined diseases is unattainable without the use of modern high-tech diagnostic methods. Accurate and timely identification of such conditions is essential for effectively managing pathological manifestations, ensuring the selection of appropriate treatment strategies, and preventing potential iatrogenic complications.