Learning Objective: At the end of this lesson, the learner will be able to identify common autosomal recessive disorders, understand their inheritance pattern, and recognize key clinical features relevant to USMLE Step 1.
High-Yield Autosomal Recessive Diseases
| Disorder | Key Features / Notes |
|---|---|
| Oculocutaneous Albinism | Tyrosinase deficiency; hypopigmentation, vision problems |
| Phenylketonuria (PKU) | Phenylalanine hydroxylase deficiency; intellectual disability, musty odor; dietary management |
| Cystic Fibrosis | CFTR mutation; thick mucus, recurrent pulmonary infections, pancreatic insufficiency, meconium ileus |
| Sickle Cell Disease | Hemoglobin S mutation; vaso-occlusive crises, hemolytic anemia |
| Wilson Disease | ATP7B mutation; copper accumulation; liver disease, neuropsychiatric symptoms, Kayser-Fleischer rings |
| Sphingolipidoses (except Fabry) | Lysosomal storage disorders: Tay-Sachs, Gaucher, Niemann-Pick |
| Hemochromatosis | HFE mutation; iron overload, cirrhosis, diabetes |
| Glycogen Storage Diseases | Enzyme defects affecting glycogen metabolism; hepatomegaly, hypoglycemia |
| Thalassemias | Reduced globin chain synthesis; anemia, splenomegaly |
| Mucopolysaccharidoses (except Hunter) | Lysosomal enzyme defects; coarse facies, skeletal abnormalities |
| Friedreich Ataxia | GAA trinucleotide repeat; progressive ataxia, cardiomyopathy, diabetes |
| Kartagener Syndrome | Dynein arm defect; situs inversus, chronic sinusitis, bronchiectasis |
| Autosomal Recessive Polycystic Kidney Disease (ARPKD) | PKHD1 mutation; bilateral enlarged kidneys, cystic dilation of collecting ducts, congenital hepatic fibrosis, hypertension; often presents in infancy |
High-Yield Tips
- AR disorders: horizontal inheritance (siblings affected, parents usually carriers).
- Typically, enzyme deficiencies, except for structural disorders like ARPKD.
- Consanguinity increases risk.
- Severity is often greater than AD disorders; childhood presentation is common.
