spastic paraplegia 90B, autosomal recessive

Summary

spastic paraplegia 90B, autosomal recessive (MONDO:0957309) is a disease with 1 cohort gene.

At a glance

• Cohort genes: 1
• ClinVar variants: 1

Clinical features

No curated clinical features (Orphanet) for this disease.

Identifiers

Disease identifiers

Field	Value
Canonical name	spastic paraplegia 90B, autosomal recessive
Mondo ID	MONDO:0957309
OMIM	620417
DOID	DOID:0070460
UMLS	C5830578
MedGen	1841214
GARD	0026816
Is cancer (heuristic)	no

Data availability: 1 ClinVar variant · 2 GenCC gene-disease records.

Disease family

Classification path: disease › human disease › disease by body system or component › nervous system disorder › central nervous system disorder › palsy › paraplegia › hereditary spastic paraplegia › spastic paraplegia 90B, autosomal recessive

Related subtypes (44): hereditary spastic paraplegia 3A, hereditary spastic paraplegia 4, mast syndrome, hereditary spastic paraplegia 5A, hereditary spastic paraplegia 16, hereditary spastic paraplegia 2, macrocephaly-spastic paraplegia-dysmorphism syndrome, Charcot-Marie-Tooth disease type 5, hereditary spastic paraplegia 6, hereditary spastic paraplegia 10, hereditary spastic paraplegia 14, hereditary spastic paraplegia 13, hereditary spastic paraplegia 7, hereditary spastic paraplegia 33, hereditary spastic paraplegia 31, hereditary spastic paraplegia 30, hereditary spastic paraplegia 35, hereditary spastic paraplegia 50, hereditary spastic paraplegia 48, hereditary spastic paraplegia 51, hereditary spastic paraplegia 47, hereditary spastic paraplegia 52, hereditary spastic paraplegia 56, early-onset progressive neurodegeneration-blindness-ataxia-spasticity syndrome, hereditary spastic paraplegia 77, pure hereditary spastic paraplegia, complex hereditary spastic paraplegia, pure or complex hereditary spastic paraplegia, spastic paraplegia 87, autosomal recessive, spastic paraplegia 80, autosomal dominant, spastic paraplegia 81, autosomal recessive, spastic paraplegia 82, autosomal recessive, spastic paraplegia 83, autosomal recessive, spastic paraplegia 88, autosomal dominant, spastic paraplegia 79A, autosomal dominant, with ataxia, spastic paraplegia 89, autosomal recessive, spastic paraplegia 90A, autosomal dominant, spastic paraplegia 91, autosomal dominant, with or without cerebellar ataxia, spastic paraplegia 72b, autosomal recessive, spastic paraplegia 92, autosomal recessive, spastic paraplegia 93, autosomal recessive, IFIH1-related hereditary spastic paraplegia, RNASEH2B-related hereditary spastic paraplegia, ADAR-related hereditary spastic paraplegia

Genetics & variants

GWAS landscape

No GWAS associations recorded — common-variant (GWAS) studies don’t cover this disease (typical for Mendelian / rare diseases). See the curated gene cohort and Mendelian overlap below.

Variant details and genetic-evidence tiers

ClinVar germline variants

1 retrieved; paginated sample, class counts are floors:

1 pathogenic

ClinVar	Variant (HGVS)	Gene	Classification	Review
2505468	NM_138288.4(SPTSSA):c.171_172del (p.Gln58fs)	SPTSSA	Pathogenic	no assertion criteria provided

Genes & proteins

Mendelian disease overlap and somatic drivers

GenCC: 4 · Orphanet: 0 · OMIM-shared: 0 · Dual-evidence (GWAS+Mendelian): 0

GenCC gene–disease validity (cohort genes)

the Disease column is the GenCC-asserted condition — a cohort gene’s strongest validity may be for a related predisposition syndrome.

Gene	Classification	Inheritance	Disease	Records
SPTSSA	Strong	Autosomal dominant	spastic paraplegia 90A, autosomal dominant	4

Cohort genes → proteins

1 cohort genes, 1 distinct canonical proteins.

Evidence partition

Subset	Genes
multi_evidence	1

Cohort genes (full)

Symbol	HGNC	Ensembl	UniProt	Name	Evidence
SPTSSA	HGNC:20361	ENSG00000165389	Q969W0	Serine palmitoyltransferase small subunit A	gencc,clinvar

Cohort function summary

Lead sentence per gene, UniProt-curated.

Symbol	Protein name	Function (lead sentence)
SPTSSA	Serine palmitoyltransferase small subunit A	Component of the serine palmitoyltransferase multisubunit enzyme (SPT) that catalyzes the initial and rate-limiting step in sphingolipid biosynthesis by condensing L-serine and activated acyl-CoA (most commonly palmitoyl-CoA) to form long-…

Protein-family classification

Druggable: 1 · Difficult: 0 · Unknown: 0 · Druggable fraction: 1.0

Family distribution

Cohort families vs a genome-wide background (hypergeometric, BH-FDR; fold = observed/expected). Counts kept; sorted by enrichment, so the catch-all Other/Unknown bucket no longer leads.

Family	Genes	Fold	FDR
Enzyme (other)	1	12.0×	0.083

Per-gene assignment

Symbol	Family	Druggable?	EC	InterPro (top 3)
SPTSSA	Enzyme (other)	yes	2.3.1.50	Ser_palmitoyltrfase_ssu-like, SPT_small_subunit

Expression context

Cohort genes with no expression data: 0.

1 cohort gene are a single-cell marker in ≥1 SCXA experiment.

Breadth distribution (Bgee present_calls)

Bucket	Genes
narrow (1-5 tissues)	0
moderate (6-20)	0
broad (>20)	1
unknown	0

Top tissues across cohort

Tissue	Cohort genes
adrenal cortex	1
mucosa of sigmoid colon	1
right adrenal gland cortex	1

Per-gene tissue summary (top 30)

Symbol	Bgee breadth	FANTOM5 breadth	SCXA	Top tissues
SPTSSA	296	ubiquitous	marker	mucosa of sigmoid colon, right adrenal gland cortex, adrenal cortex

Protein interactions among cohort

Intra-cohort edges: 0.

Hub genes (top 10 by interactor count)

Symbol	Interactor count
SPTSSA	453

Structural data

PDB: 1 · AlphaFold-only: 0 · No structure: 0

Cohort genes with PDB structures (top 30)

Symbol	UniProt	PDB entries
SPTSSA	Q969W0	17

Function

Pathway analysis

Distinct Reactome pathways touched by cohort: 4. Enrichment computed across 1 evidence-associated genes (1 with Reactome annotation).

Pathways by enrichment

Over-representation of cohort genes vs the genome-wide background (hypergeometric test, Benjamini-Hochberg FDR; fold = observed/expected over 1 annotated cohort genes). Counts and members are kept as ground-truth; sorted by enrichment.

Pathway	Cohort genes	Fold	FDR	Sample cohort genes
Sphingolipid de novo biosynthesis	1	285.5×	0.012	SPTSSA
Sphingolipid metabolism	1	167.9×	0.012	SPTSSA
Metabolism of lipids	1	31.6×	0.042	SPTSSA
Metabolism	1	11.6×	0.086	SPTSSA

GO biological processes by enrichment

Over-representation of cohort genes vs the genome-wide background (hypergeometric test, Benjamini-Hochberg FDR; fold = observed/expected over 1 annotated cohort genes). Counts and members are kept as ground-truth; sorted by enrichment.

GO term	Cohort genes	Fold	FDR	Sample cohort genes
sphingosine biosynthetic process	1	1053.2×	0.004	SPTSSA
ceramide biosynthetic process	1	421.3×	0.004	SPTSSA
sphingolipid biosynthetic process	1	358.6×	0.004	SPTSSA
intracellular protein localization	1	104.7×	0.010	SPTSSA

Therapeutics

Drug target analysis

Approved (phase 4): 0 · Phase ≥3: 0 · Phased (≥1): 0 · Undrugged: 1

Druggability breadth: 0 of 1 evidence-associated genes (0%) have a ChEMBL target (buckets above are over the deeply-mined display cohort).

Top cohort targets by molecule count

Symbol	Molecules	Max phase
SPTSSA	0	0

Bioactivity and enzyme data

Enzyme cohort genes (≥1 EC): 1.

Cohort enzymes (BRENDA EC)

Symbol	EC numbers	Names
SPTSSA	2.3.1.50	serine C-palmitoyltransferase

Pharmacogenomics

Cohort genes with a PharmGKB record: 1; with CPIC/DPWG dosing guidelines: 0.

No cohort gene has a CPIC/DPWG genotype-guided dosing guideline (PharmGKB).

Chemical tractability of cohort targets

0 approved/phased compounds have measured bioactivity against a cohort gene (and aren’t yet in disease-level trials). This is a research / tractability signal, NOT a therapeutic recommendation — a bioactivity row often reflects off-target or screening binding (e.g. promiscuous kinase inhibitors against a cohort kinase), implying no disease mechanism.

Druggability pyramid

Cohort genes binned by druggability tier (high → low):

Tier	Definition	Genes	Symbols
A	Approved (phase 4 drug)	0
B	Phased (≥1) drug, not yet approved	0
C	Druggable family + PDB, no drug	1	SPTSSA
D	Druggable family + AlphaFold only, no drug	0
E	Difficult family or no structure, no drug	0

Undrugged target profiles

1 cohort genes are undrugged. Ranked by ‘starting-point quality’ (assay depth + drugged-partner adjacency).

Symbol	ChEMBL assays	Drugged partners (top 3)
SPTSSA	0	—

Clinical trials & evidence

Clinical trials

Clinical trials: 0.