Hoyeraal-Hreidarsson Syndrome (HHS) is a severe X-linked multi-system disorder that is associated with microcephaly, delays in intrauterine growth, intellectual disability, spastic paresis, ataxia, and immunodeficiency. Other clinical manifestations include hyperpigmentation; nail dystrophy, oral and premalignant leukoplakia affecting oral and gastrointestinal mucosa. Affected individuals have an unusually small and underdeveloped cerebellum, which is the part of the brain that coordinates movement. People with HHS usually develop early onset bone marrow failure, immunodeficiency and pancytopenia. HHS is caused by mutations in the DKC1 gene.
DIAGNOSTIC TESTING, PHYSICAL FINDINGS, AND ICD-9-CM CODING
Diagnostic testing: Neuroimaging reports showing cerebellar hypoplasia/atrophy, small brainstem, thin corpus callosum and cerebral calcifications. Genetic testing for the DKC1 gene confirms the clinical diagnosis.
Physical findings: Individuals with HHS are at risk for progressive bone marrow failure, myelodysplastic syndrome or acute leukemia, solid tumors of the head/neck, pulmonary fibrosis, and abnormal pigmentation changes to the upper chest/neck, eye abnormalities, dental abnormalities, developmental delay, cerebellar hypoplasia, bilateral exudative retinopathy, and intracranial calcifications.
ICD-9: 284 (Constitutional aplastic anemia); 287.33
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