Table 2.

Psychiatric examination, family history, somatic and neuropsychological findings.

Psychiatric examination	•Attention and concentration deficits, memory difficulties, affective instability, impulsive behaviors and sensory overload. •No depressiveness, no anxiety, no delusions/hallucinations, no suicidal tendencies, no sleep disorders, normal appetite.
Physical examination	•Internal: Normal internal investigation. •Dermatological: Diffuse hyperpigmentation, periorbital melasma, discreet acne (most likely steroid-triggered), xerosis skin, secondary hair was reduced. •Neurological: Monopod right somewhat plumped up, muscle self-reflexes at the upper and lower extremities right-emphasized, the remaining neurostatus was inconspicuous.
Family history	•Mother, sister, and maternal grandfather suffered from type 1 diabetes mellitus. Maternal grandfather died of kidney failure. •Several family members suffer from hearing impairments (paternal great-grandmother, paternal grandfather and grandmother, father; no investigations for underlying reason carried out). Paternal grandfather developed dementia in old age and presently suffers from bronchial carcinoma in his advanced age. •In terms of body height our patient was 172 cm tall but still the shortest in her family, her one sister is 174 cm (24 years), her other sister is 180 cm (22 years). Her parents are measuring both about 180 cm.
Genetic testing*	•Heteroplasmic base exchange mutation in the MT-ND4 gene (m.12015T>C; p.Leu419Pro); MAF >0.01%; heteroplasmy level in the blood: 12%, in the muscle tissue 15%. •In the POLG gene, the well-known polymorphism c.156_158delGCA; p.Q55del (rs727504102) was found in heterozygous state.
Basic blood/urine analyses	•Blood cell count, electrolytes, liver/kidney/pancreas values, HbA1c, and folic acid were normal. Vitamin B12 was elevated under substitution (3,106 pg/ml; reference 197–771 pg/ml). Selenium was slightly reduced (68 μg/l; reference: 75–140 μg/l) •Thyroid-stimulating hormone and triiodothyronine levels were in normal ranges. Thyroxine was slightly increased under substitution: 22.2 pmol/l; reference: 12–22 pmol/l). •Normal blood glucose day profile. •Testosterone was not measurable (< 0.087 nmol/l). •ACTH in the morning (at 8 o'clock) was increased (243 pg/ml, reference: 10–60 pg/ml). •The urine analyses showed slightly increased albumin creatinine quotient (29 mg/g creatine). The urine-stix was slightly positive for protein (+) and negative for blood.
Immunological blood testing	•No antibodies against the intracellular onconeural antigens Yo, Hu, CV2/CRMP5, Ri, Ma1/2, SOX1 or the intracellular synaptic antigen amphiphysin were found. Anti-GAD65 antibodies were positive (quantification with ELISA-technique showed concentrations of 113 U/ml; reference < 2 U/ml). •Antibodies against neuronal cell surface antigens (NMDAR, AMPA-R, GABA-B-R, VGKC-complex [LGI1, Caspr2]) were negative. •Autoantibodies against thyroglobulin (329.3 IU/ml; reference < 115 IU/ml) and thyroid peroxidase (401 IU/ml; reference: < 34 IU/ml) were increased. Antibodies against the TSH receptor were normal. Adrenal cortex antibodies were increased (1:30; reference < 1:10). •Anti-partial cell and anti-intrinsic factor antibodies were positive. Anti-insulin and anti-IA2 antibodies were not increased. •Screening for antinuclear antibodies (ANA) in IIF showed a homogeneous nuclear fluorescence with a chromosomal pattern (1:200). Testing for extractable nuclear antibodies (ENA) showed no antibody specificity including anti-DFS-70 antibodies. Anti-neutrophil cytoplasmic antibodies, antiphospholipid antibodies, rheumatoid factor, and anti-mitochondrial antibodies were negative. •No changes in the complement system (C3, C4, CH50, C3d) were observed. •Serum immunoglobulin concentrations: 10.4 g/L IgG (reference 7.00–16.00 g/L), 1.05 g/L IgM (reference 0.7–4.0 g/L), 1.75 g/L IgA (reference 0.4–2.3 g/L). Immunofixation showed no monoclonal antibody production. •Lymphocyte and B-cell panel showed slightly increased levels of CD3+t-cells (84.1% reference: 55–83%), CD3+CD4+t-cells 58.2% (reference: 28–57%), clearly increased number of IgD-CD27+B-cells (29.88%, reference 5.7–24%), IgA+CD27+memory B-cells (14.72%, reference 2.8–10.9), and IgM+/-CD38++plasma blasts of B-cells (8.75%, reference 0.2–3.4%). CD65+CD16+natural killer cells (72/micro l, reference: 90–600/micro l) and CD56+CD16+natural killer cells (4.5%, reference: 7–31%) were reduced. All other cells were in the normal range.
Cerebrospinal fluid analyses	•Normal white blood cell count (1/μL; reference < 5/μL). •Normal protein concentration (247 mg/L; reference < 450 mg/L), and normal age-corrected albumin quotient: 2.5; age-dependent reference < 6.5 × 10−3). •No CSF specific oligoclonal bands; IgG index not increased (0.6; reference < 0.7). •CSF lactate normal (1.87 mmol/l; reference 1,5-2,1 mmol/L). •Antibodies against neuronal cell surface antigens (NMDAR, AMPA-R, GABA-B-R, VGKC-complex [LGI1, Caspr2]) were negative.
Cerebral magnetic resonance imaging (Figure 2)	•Substance defect of the parietooccipital left side exceeding the vascular territories with signs of chronic hemorrhagic transformation. •Small cortical/subcortical defects right temporal and frontoinsular. Cortical siderosis of a defect in the praecentral gyrus on the right and parietooccipital left.
Magnetic resonance spectroscopy** (Figure 5)	•Single-voxel magnetic resonance spectroscopy results show slightly higher Lac+/Cr concentration ratio compared to control subjects: In the orbitofrontal cortex (OFC), a Lac+/Cr concentration ratio of 0.182 was found compared to a control group (males: N = 5, females: N = 1; 28 ± 2 years; Figure 5) with 0.159 ± 0.01, in the dorsal anterior cingulate cortex (dACC) 0.202 compared to 0.188 in one control subject (male, 31years) and in the dorsolateral prefrontal cortex (DLPFC) 0.172 compared to 0.168 in one control subject (male, 27years).
Electroencephalography	Alpha-rhythm, intermittent slowing accentuated left parieto-occipital; no epileptic patterns (under the treatment with high dose levetiracetam).
Electromyography	In the right anterior tibial muscle insertion activity was normal. No spontaneous activity. Evaluation of motor unit potentials revealed mild myopathic changes.
Lactate ischemia test	•Aerobic continuous load on the bicycle ergometer for 15 min at 30 watts: Resting lactate: 0.84 mmol/l, after 5 min: 2.35 mmol/l, after 10 min: 3.04 mmol/l, and after 15 min 3.25 mmol/l. •There was a continuous increase in heart rate over the course of 15 min.
Magnetic resonance imaging of thigh and lower leg	•Normal muscle signals.
Muscle biopsy	•Discrete substrate redistribution with partly sub-sarcolemmal, cap-like substrate propagation in the oxidative enzyme reactions, however, clear “ragged red/blue fibers” cannot be detected here. However, single COX-negative muscle fibers can be detected. •Ultrastructurally, small mitochondrial accumulations with individual, partly swollen, mitochondria can be found, but paracrystalline inclusions cannot be detected here. In addition, a discrete type 2 fiber atrophy can be detected.
Ophthalmological examinations	•Clinical ophthalmological examination was inconspicuous. •Macular scans were performed using spectralis optical coherence tomography device (spectral-domain OCT). Both eyes showed normal retinal volume and normal full retina thickness in all subfields with reference to normative data given by Nieves-Moreno et al. (11). •For visual electrodiagnostic testing light adapted electroretinogram was recorded from both eyes using RETeval device from LKC-Technologies. Both eyes showed normal cone function in response to the photopic-flash protocol and normal ganglion cell function with the stimulation protocol for the photopic negative response. Normative data were provided by LKC-Technologies (https://www.lkc.com/reteval-device-normative-data/).
Heart examinations	•Inconspicuous resting electrocardiography (ECG). The long-term ECG measurement showed a sinus rhythm with intermittent tachycardic pulse; no relevant pauses. •No ischemic changes and no load-inducible rhythm disturbances occur in the ECG during the lactatischemia test. •Transthoracic echocardiography was normal. •The external CT angiography of the thorax showed no detection of coronary anomalies***.
Otorhinolaryngologic examination	•Normal findings, no hearing impairment.
Ultrasound of the carotides	•Only increased flow velocities are noticeable in the arteria cerebri media and anterior cerebral artery on the right side****.
Thyroid sonography	•Echo-poor parenchyma and inhomogeneous perfusion. No noddings. Compatible with autoimmune thyroiditis*****.
Gastroscopy	•Mild chronic, inactive antral gastritis with foveolar hyperplasia. Clear chronic, moderately active corpus gastritis with intestinal metaplasia of the paneth- and bursa cell type.
Neuropsychological tests	•Test for attention performance: Borderline average/below average tonic alertness. Phasic alertness was found to be ordinary, the ability to increase response readiness was uncompromised. She exhibited an ordinary set-shifting ability/cognitive flexibility in the presence of an above average speed-accuracy trade-off index (T = 64) indicating a slowing in response times to increase response accuracy. She showed significant impairments in divided attention (visual and auditory stimuli combined) and working memory functions (2-back task). Performance was ordinary in both the simple (1 out of 2) and the complex (2 out of 5) go/no-go task. •Culture Fair Intelligence Test-20: Results suggested an intelligence level in the lower normal range (IQ = 86) which appeared discrepant with the patient's educational background (may also be attributed to fluctuations in attention). •Route learning task: She was able to spontaneously recall the learned route correctly. She did not deviate from the route and therefore required no assistance by the experimenter. In the route recognition trial, she correctly identified the previously learned route as such. When asked to recall the designated landmarks, she spontaneously recalled eight out of the ten landmarks. In the cued condition, she recalled nine out of ten landmarks correctly. In the image-based recognition trial, she identified all landmarks as such. None of the distractor items were erroneously labelled as landmarks, resulting in a recognition accuracy of 100%. When tested 1 week later, she still recalled the route without error. •Verbal fluency: Was found to be below average in all subtests (words with S, category animals, alternating words with G-R, alternating categories sports-fruits). •Zoo map test: Revealed impairments in spontaneous planning ability. She was able to solve the given task correctly but only after amount of time (~8 min). When provided with a strategy (i.e., the correct sequence of stops on the map), she solved the task correctly in under 2 min. •Verbal learning and memory test: She showed ordinary verbal learning performance (T = 48) reproducing a total of 55 words (7-10-13-13-12) over the course of the five learning trials. Relative delayed recall performance (-2 words, T = 55) and passive recognition performance (T = 53) were ordinary. •Visual reproduction task: She exhibited quantitatively normal visual learning performance. Immediately after the learning trial, she recalled all geometric figures (38/41 points, T = 58). Delayed recall performance was similar (37/41 points, T = 49). Despite ordinary quantitative results, she made errors only with regard figure proportions but not figure components or their placement.

The investigations were performed in August /September 2018 (a half year after the stroke like episodes and the Addison crisis).

^*The following regions were analyzed (in an external laboratory for human genetics): MT-ATP6, MT-ATP8, MT-CO1, MT-CO2, MTCO3, MT-CYB, MT-ND-1, MT-ND2, MT-ND3, MT-ND4, MT-ND4L, MT-ND5, MT_ND6, MT-RN1, MT-RNP2, MT-TA, MT-TC, MT-TD, MT-TE, MT-TK, MT-TL1, MT-TL2, MT-TM, MT-TN, MT-TP, MT-TQ, MT-TR, MT-TS1, MT-TS2, MT-TT, MT-TV, MT-TW, MT-TY (mitochondrial DNA) and POLG (mitochondria-related nuclear DNA).

^**Single-voxel magnetic resonance spectroscopy (MRS) examinations were performed in three prefrontal regions (orbitofrontal cortex [OFC], dorsal anterior cingulate cortex [dACC] and dorsolateral prefrontal cortex [DLPFC]) using a MEGA-sLASER difference editing sequence (12, 13), which is suitable for more robust lactate (Lac) quantification than is achievable with standard MRS protocols. Spectral quantification was performed with LCModel (14), using numerically simulated metabolite basis spectra, and Lac concentrations were reported as ratios to creatine (Cr). Since the Lac quantification results are slightly biased due to spectral overlap with coedited macromolecular resonances, the Lac concentration was denoted by Lac+ (15). The measured Lac+/Cr concentration ratios were compared with ratios obtained from healthy control subjects with the same protocol.

^***Already performed outside in October 2017.

^****Already performed outside in February 2018.

^*****Already performed outside in March 2018.