A Patient with Glucocorticoid Hypersensitivity Syndrome

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A Patient with Glucocorticoid Hypersensitivity Syndrome

Glucocorticoid hypersensitivity syndrome is an exceptionally rare disorder characterized by heightened tissue responsiveness to physiological levels of glucocorticoids. This condition enables low endogenous cortisol concentrations to exert excessive biological effects, suppressing the hypothalamic-pituitary-adrenal (HPA) axis while paradoxically manifesting symptoms of Cushing syndrome. A recent case study provides critical insights into the diagnostic challenges, molecular mechanisms, and management strategies for this underrecognized disorder.

Clinical Presentation and Initial Investigations
A 25-year-old male presented with progressive weight gain and classic Cushingoid features, including central obesity, a cervical buffalo hump, facial rounding with acne, abdominal purple striae (1.5 cm in width), and marginally elevated blood pressure (131/90 mmHg). Laboratory and imaging evaluations revealed multisystem involvement:

  • Dual-energy X-ray absorptiometry detected reduced bone mineral density.
  • Oral glucose tolerance testing confirmed impaired glucose tolerance.
  • Baseline plasma cortisol and adrenocorticotropic hormone (ACTH) levels were at the lower end of normal ranges.
  • 24-hour urinary free cortisol excretion was consistently subnormal across four separate measurements.
  • Overnight 1 mg dexamethasone suppression test demonstrated abnormally low post-dexamethasone cortisol (1.0 μg/dL), indicating exaggerated HPA axis suppression.

Advanced imaging modalities, including pituitary MRI, adrenal CT, and whole-body PET-CT, excluded common etiologies of hypercortisolism such as pituitary adenomas, adrenal tumors, and ectopic ACTH-secreting neoplasms.

Differentiating Between Exogenous Glucocorticoid Exposure and Endogenous Hypersensitivity
The combination of clinical hypercortisolism with biochemical hypocortisolism raised two primary considerations: surreptitious glucocorticoid use or intrinsic glucocorticoid hypersensitivity. A comprehensive exclusion protocol was implemented:

  1. Pharmacological screening: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) excluded 35 common exogenous glucocorticoids and their metabolites.
  2. Psychological evaluation: No evidence of factitious disorder (Munchausen syndrome) or abnormal medication-seeking behavior.
  3. Inpatient monitoring: Persistently undetectable plasma cortisol during a 14-day hospitalization without adrenal insufficiency symptoms eliminated the possibility of intermittent exogenous administration.

Functional Validation of Glucocorticoid Hypersensitivity
To confirm altered glucocorticoid sensitivity, researchers conducted ex vivo stimulation experiments using the patient’s peripheral blood mononuclear cells (PBMCs). Key findings included:

  • Gene expression profiling: The glucocorticoid-responsive genes FKBP5 and GILZ showed significantly elevated mRNA expression in the patient compared to controls when exposed to 100 nmol/L hydrocortisone (6-hour exposure):
    • FKBP5: 3.8-fold increase vs. 1.9-fold in controls (P < 0.01)
    • GILZ: 5.2-fold increase vs. 2.7-fold in controls (P < 0.001)
  • Dose-response characteristics: Maximal transcriptional activation occurred at hydrocortisone concentrations 10–100 times lower than required for typical cellular responses.

Genetic Characterization and Molecular Mechanisms
Whole-exome sequencing and targeted PCR analyses investigated potential genetic contributors:

  1. NR3C1 variants:
    • No pathogenic mutations in the glucocorticoid receptor (GR)-α ligand-binding domain (including the N363S polymorphism).
    • Homozygous BclI intronic variant (rs41423247) detected, a single-nucleotide polymorphism associated with enhanced glucocorticoid sensitivity in epidemiological studies.
  2. Receptor expression dynamics:
    • Total NR3C1 mRNA expression in PBMCs was reduced to 40% of parental/control levels.
    • No significant alterations in GRα/GRβ isoform ratios despite overall receptor downregulation.

This receptor paradox—diminished total GR expression with preserved hypersensitivity—suggests compensatory upregulation of post-receptor signaling components or ligand-independent GR activation pathways. The observed BclI polymorphism may modify chromatin accessibility or mRNA splicing efficiency, though precise mechanistic links remain undefined.

Diagnostic Algorithm Development
Based on this case and literature review, the authors propose a standardized diagnostic pathway for glucocorticoid hypersensitivity (Supplementary Figure 1D):

  1. Clinical suspicion: Cushingoid features with discordantly low/normal cortisol and ACTH.
  2. Exclusion of mimickers:
    • Three negative LC-MS/MS assays for synthetic glucocorticoids.
    • Extended inpatient observation with serial cortisol/ACTH profiling.
    • Psychological assessment for factitious disorder.
  3. Functional confirmation:
    • In vitro glucocorticoid response assays using patient-derived cells.
    • Gene expression analysis of FKBP5 and GILZ as sensitivity biomarkers.
  4. Genetic characterization:
    • Targeted sequencing of NR3C1 and related regulatory regions.
    • Assessment of BclI, ER22/23EK, and A3669G polymorphisms.

Therapeutic Considerations
Management strategies aim to counteract pathological GR signaling while preserving essential glucocorticoid functions:

  1. GR antagonists:
    • Mifepristone (competitive GR antagonist) shows therapeutic promise, with prior case reports demonstrating improvements in metabolic parameters and Cushingoid features.
  2. Adjunctive therapies:
    • Metformin and antihypertensives addressed secondary metabolic complications in the present case.
  3. Monitoring challenges:
    • Serum cortisol becomes unreliable as a biomarker during GR antagonist therapy.
    • Bone mineral density tracking and continuous glucose monitoring provide alternative outcome measures.

Long-term Follow-up and Prognosis
The patient maintained stable clinical status over 12 months with conservative management, highlighting the indolent but persistent nature of this condition. Serial assessments showed:

  • No progression of bone density loss or glucose intolerance.
  • Persistent hypocortisolism (morning cortisol 2.1–3.8 μg/dL) without adrenal crisis.
  • Stable BclI polymorphism status on repeat genotyping.

Implications for Clinical Practice
This case redefines the diagnostic paradigm for atypical Cushing syndrome presentations:

  1. Glucocorticoid hypersensitivity should be considered in euthyroid patients with Cushingoid features and unexplained hypocortisolism.
  2. Functional cellular assays complement traditional biochemical testing when genetic results are inconclusive.
  3. The BclI polymorphism serves as a susceptibility marker rather than a definitive diagnostic criterion, requiring integration with phenotypic data.

Future Research Directions
Unresolved questions motivate ongoing investigations:

  • Development of tissue-specific glucocorticoid sensitivity assays.
  • Pharmacogenomic studies to optimize mifepristone dosing based on GR polymorphisms.
  • Exploration of GR chaperone proteins (e.g., FKBP5) as therapeutic targets.
  • Induced pluripotent stem cell models to study GR signaling dynamics across cell lineages.

This landmark case establishes a framework for recognizing and managing glucocorticoid hypersensitivity, emphasizing the importance of molecular diagnostics in endocrinology. By delineating the intricate interplay between receptor genetics, cellular physiology, and clinical presentation, it advances our understanding of glucocorticoid signaling pathologies.

doi.org/10.1097/CM9.0000000000001977

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