Unexpected Diagnosis of Fahr's Disease in a Patient with Severe Obesity and a Heterozygotic Variant in the TMEM67 Gene.

Objective: The genetic causes of obesity are complex and include diabetes and obesity monogenic syndromes like autosomal recessive Bardet-Biedl syndrome (BBS). Other clinical manifestations of this syndrome include metabolic disorders, polydactyly, retinal dystrophy, and endocrine, urological, and neurological abnormalities. Moreover, isolated clinical manifestations have been described in carriers of heterozygous mutations in BBS genes. On the other hand, Fahr's disease is characterized by the accumulation of calcium deposits in various areas within the brain, leading to neurodegeneration, and the course of the disease is variable. Case presentation: We present the case of a 21-year-old female with severe obesity, diagnosed at the age of six years. The patient also experienced hypertension, hyperlipidemia, insulin resistance, and polycystic ovarian syndrome. During an MRI examination, hyperintensity in the region of the dentate nuclei and hyperintensity in the globus pallidus were described. NGS (next-generation sequencing) results showed a heterozygous variant in the TMEM67 gene, which revealed the patient to be a carrier of BBS, and a homozygotic variant in the MYORG gene, leading to a Fahr's disease diagnosis. However, due to an insufficient number of phenotypic criteria and only one causative variant in the TMEM67 gene, the diagnosis of BBS could not be established. Conclusions: Attempts to identify the cause of obesity can lead to unexpected results, which can be resolved through collaboration between clinicians of different specialties and the use of NGS molecular testing. The status of being a BBS carrier, which coexists with Fahr's disease, may be a potential contributing factor to severe obesity and metabolic disorders in the patient.