Lysosomal storage diseases
📖 Overview
- 🧬 Lysosomal storage diseases (LSDs) = inherited metabolic disorders caused by defective lysosomal enzymes.
- 🧪 Enzyme deficiency → accumulation of substrates → cell & organ damage.
- 👨👩👧 Most follow an autosomal recessive pattern (25% risk if both parents carriers).
- 🌍 Higher prevalence in certain groups (e.g., Ashkenazi Jewish population with genetic screening).
🧾 Major Types
🥼 Gaucher Disease
- 🔬 Cause: Deficiency of glucocerebrosidase.
- 🩺 Features: Hepatosplenomegaly, bone pain, anaemia, thrombocytopenia, fractures.
- 💊 Treatment: Enzyme replacement therapy (ERT), substrate reduction therapy (SRT), bisphosphonates, supportive care.
👁️ Tay–Sachs Disease
- 🔬 Cause: Deficiency of hexosaminidase A.
- 🩺 Features: Neurodegeneration, cherry-red macula spot, muscle weakness, seizures, blindness, deafness.
- 💊 Treatment: Supportive only (feeding support, anticonvulsants, physio); no cure.
❤️ Fabry Disease
- 🔬 Cause: Deficiency of alpha-galactosidase A.
- 🩺 Features: Pain (hands/feet), angiokeratomas, renal & cardiac disease, gut issues, hypohidrosis, corneal clouding.
- 💊 Treatment: ERT, pain management, cardiovascular/renal monitoring, genetic counselling.
💪 Pompe Disease
- 🔬 Cause: Deficiency of acid alpha-glucosidase.
- 🩺 Features: Muscle weakness, respiratory failure, cardiomegaly (infantile form), swallowing difficulty.
- 💊 Treatment: ERT, respiratory support, physio, dietary adjustments, supportive care.
🦴 Mucopolysaccharidoses (MPS)
- 🔬 Cause: Enzyme deficiencies in glycosaminoglycan (GAG) breakdown.
- 🩺 Features: Skeletal dysplasia, organomegaly, developmental delay, airway obstruction, vision/hearing loss.
- 💊 Treatment: ERT, bone marrow transplant, surgery (airway/skeletal), physio.
🔎 Diagnosis
- 📜 Family history + genetic counselling.
- 🩺 Clinical assessment of symptoms & progression.
- 🧪 Enzyme assays to measure activity.
- 🧬 Genetic testing for mutations.
- 🖼️ Imaging (MRI/CT) for organ involvement.
💊 Treatment & Management
- Enzyme Replacement Therapy (ERT) 💉 → restores deficient enzyme (Gaucher, Fabry, Pompe).
- Substrate Reduction Therapy (SRT) ⚖️ → decreases substrate production.
- Hematopoietic Stem Cell Transplantation (HSCT) 🧫 → donor marrow produces functional enzymes (e.g., MPS).
- Supportive Care 🤲 → pain control, physio, nutritional support, cardiac/respiratory management.
- Gene Therapy 🧬✨ → experimental but promising in trials.
📌 Summary
- LSDs = inherited enzyme deficiencies → lysosomal substrate accumulation.
- ⚠️ Early recognition improves quality of life & prevents irreversible organ damage.
- ERT is cornerstone; SRT, HSCT, & gene therapy are evolving options.
- 🚀 Research continues to expand treatments & improve outcomes.
Cases - Lysosomal Storage Diseases
- Case 1 - Gaucher disease (Glucocerebrosidase deficiency) 🦴: A 6-year-old Ashkenazi Jewish boy presents with hepatosplenomegaly, easy bruising, anaemia, and bone pain. Bloods: pancytopenia. Bone marrow: “crumpled tissue paper” macrophages. Diagnosis: Type 1 Gaucher disease. Managed with enzyme replacement therapy (imiglucerase).
- Case 2 - Tay–Sachs disease (Hexosaminidase A deficiency) 👁️: A 9-month-old girl presents with developmental regression, hypotonia, exaggerated startle reflex, and seizures. Ophthalmoscopy: cherry-red spot at macula. Family history: Ashkenazi descent. Diagnosis: Tay–Sachs disease. No curative treatment; supportive and palliative care provided.
- Case 3 - Hurler syndrome (Mucopolysaccharidosis type I, α-L-iduronidase deficiency) 🧬: A 3-year-old boy presents with coarse facial features, corneal clouding, recurrent ear infections, hepatosplenomegaly, and developmental delay. Radiographs: dysostosis multiplex. Diagnosis: Hurler syndrome. Managed with enzyme replacement therapy and haematopoietic stem cell transplantation in selected cases.
Teaching Point 🩺: Lysosomal storage diseases are inherited metabolic disorders caused by enzyme deficiencies → accumulation of unmetabolised substrates.
Key examples:
- Gaucher: bone pain, cytopenias, hepatosplenomegaly.
- Tay–Sachs: neurodegeneration, cherry-red spot.
- Hurler: coarse facies, corneal clouding, skeletal deformities.
Diagnosis: enzyme assay, genetic testing.
Management: enzyme replacement, HSCT, supportive therapies. Prognosis varies by subtype.
