# New Insights into the Neuromyogenic Spectrum of a Gain of Function Mutation in SPTLC1
## 3 Results
### Microscopic Findings on a Quadriceps Biopsy Derived from the p.(A20S)-Sptlc1-Patient  
Nicotinamide adenine dehydrogenase trichrome (NADH-TR) staining revealed mild subsarcolemmal accumulation of substrate in a proportion of muscle fibers (Figure 3). The same finding was obtained by succinate dehydrogenase (SDH) stain and combined cytochrome oxidase and succinate dehydrogenase (COX-SDH) stains (Figure 3). Adenosine triphosphatase (ATPase) staining (pH 4.3--not stained = type II/dark = type I, pH 4.6--subtyping type IIa = pale and IIb = intermediate, dark = type I, pH 9.4--pale type I/dark type II) indicated fiber-type grouping in addition to small fibers of either fiber type (Figure 3), as known pathological hallmarks of denervated muscle. Immunohistochemistry studies revealed irregular Troponin-T distribution (Figure 3). Myosin heavy chain fast (MHCf)  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Protein** & **Gene Name** & **Protein Name** & **Unique** & **Fold of** & **\(p\)-Value** & **Neurological** & **OMIM** \\
**Accession** & & & & **Peptides** & **Decrease** & **Disease** & **OMIM** \\ \hline \multirow{3}{*}{Q9 HA77} & \multirow{3}{*}{CARS2} & Probable & & & & Combined & & \\  & & cysteine-tRNA & & & & oxidative & COXPD27; & \\  & & ligase, & & & phosphorylation & & MIM6:16672 \\  & & mitochondrial & & & & deficiency 27 & \\ \hline \multirow{3}{*}{Q9 NVH6} & \multirow{3}{*}{TMLHE} & Trimethyllysine & & & & & & \\  & & dioxygenase, & & & & & \\  & & mitochondrial & & & & & & \\ \hline \multirow{3}{*}{Q9 UUJ6} & \multirow{3}{*}{ZMIZ1} & Zinc finger & & & & & & \\  & & MIZ domain- & & & & & & \\  & & containing & & & & & & \\  & & protein 1 & & & & & & \\  & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\ Q92643 & \multirow{3}{*}{PIGK} & GPI-anchor & & & & & & & NEDHCAS; \\  & & transamidase & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\ Q96582 & \multirow{3}{*}{PIGS} & GPI & & & & & & & \\  & & transamidase & & & & & & \\  & & &  
(demonstrating dark type II fibers, and conversely Myosin heavy chain slow (MHCs) demonstrating dark type I fibers illustrate both the grouping and small, often scattered or also grouped, atrophic fibers of either fiber type. Immature MHC developmental or MHC neonatal-positive fibers were apparent only scarcely. The immunohistochemical analysis of the skeletal muscle indicated single CD3+ T cells in the endomyosin and the perimysium focally (Figure 4) Few CD68+ macrophages were identified within and adjacent to an intramuscular nerve fascicle (Figure 4). Except the physiological expression within the perineurium of the nerve, no C5b-9 deposition  
Figure 3: Light microscopic (histology and immunohistology) findings in a quadriceps muscle biopsy derived from the p.(A20S)-SPTLC1-patient: Enzyme histochemical NADH-TR, SDH, and COX-SDH preparations indicating mild subsarcolemmal accumulation of substrate in single fibers (arrows). Grouping and atrophy of fibers of either fiber types are highlighted with ATPase preparations incubated at different pH levels, like the immunohistochemical MHC fast and –slow stains (arrows indicating atrophic type I and II fibers. Only single immature fibers expressing MHC-developmental or –neonatal. Troponin T indicates some mildly irregular staining on atrophic fibers (arrows). was present (Figure 4). However, adjacent to this nerve, some single perifascicular muscle fibers indicated sarcolemmal expression of MHC-cl. I (Figure 4) which was also present on some macrophages. Moreover, macrophages expressed MHC-cl. II and some enlarged capillaries were also MHC cl. II-positive (Figure 4). Numerous small, CD56+-regenerating muscle fibers were identified (Figure 4). No cell infiltration or immune reactivity to any of the investigated molecules was observed in other areas of the biopsy.