A 60-year-old deep-sea captain with a diagnosis of MS presented to the tertiary hospital for further investigations of cognitive decline. His first symptoms were temporally related by his family to an incident a decade previously when his ship caught fire during the Gulf War, and he was exposed to smoke and fumes without being able to leave the ship for weeks. After this traumatic experience, he started to complain of progressive bladder and sexual dysfunction, problems with dexterity, and gait disturbance. After investigation, he was diagnosed with MS at the age of 52. Concurrent with the development of physical symptoms, the family also noted impaired naming and word-finding difficulties, manifesting as circumlocutions in conversations. Later, more pronounced deficits in comprehension of language, object-recognition, and surface dyslexia manifested, causing great distress to the patient and his family and leading him to retire early. His visuospatial skills, phonological and syntactic processes, and, to some extent, episodic memory, were initially spared. There was no other personal or family history of note. On examination, he had mild weakness in his right lower limb, brisk reflexes, and bilateral up-going plantar responses. Blood screen, including treponemal serology, was negative, but CSF showed IgG oligoclonal bands. Neuroimaging revealed periventricular white-matter lesions, as well as asymmetric frontotemporal atrophy, more pronounced on the left, and disproportionate to the number of white-matter lesions. Neuropsychological testing showed a verbal IQ of 69 and performance IQ of 86. His verbal subtest scores ranged from extremely low (Vocabulary and Similarities) to average (Digit Span). He also had extremely low scores on the Picture Completion performance test, while scoring high-average on Matrix Reasoning. Verbal recognition was less efficient than visual recognition-memory. The possibility of a dual neurological diagnosis of MS and a frontotemporal-dementia-spectrum disorder was considered likely. He was started on galantamine, but continued to deteriorate physically, cognitively, and behaviorally over the next 3 years, necessitating residential placement, where he eventually died. Postmortem histopathological examination disclosed two distinct and separate pathologies: MS and widespread TDP-43 proteinopathy. Severe neuronal loss was found in the left temporal cortex with an anterior gradient (Figure 1 [A]). The rest of the brain showed moderate cortical atrophy, with white-matter loss. The MS mainly affected the spinal cord and brainstem (Figure 1 [B]). There were widespread TDP-43-positive dystrophic neurites, no intranuclear, and only rare intracytoplasmic inclusions in the neurones of neocortex and limbic system, in keeping with frontotemporal lobar degeneration with TPD-43 proteinopathy (FTLD-TDP43) subtype 1 (Figure 1 [C]).