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Genetics Home Reference: X-linked infantile spinal muscular atrophy

X-linked infantile spinal muscular atrophy is a condition that affects only boys and is characterized by severe muscle weakness and absent reflexes (areflexia). Affected children often have multiple joint deformities (contractures) from birth that cause joint stiffness (arthrogryposis) and impair movement. In severe cases, affected infants are born with broken bones. The muscle weakness worsens… Read More »

Genetics Home Reference: systemic mastocytosis

Systemic mastocytosis is a blood disorder that can affect many different body systems. Individuals with the condition can develop signs and symptoms at any age, but it usually appears after adolescence. Signs and symptoms of systemic mastocytosis often include extreme tiredness (fatigue), skin redness and warmth (flushing), nausea, abdominal pain, bloating, diarrhea, the backflow of… Read More »