Lowe syndrome (oculocerebrorenal syndrome) is characterized by involvement of the eyes, central nervous system, and kidneys. Dense congenital cataracts are found in all affected boys and infantile glaucoma in approximately 50%. All boys have impaired vision; corrected acuity is rarely better than 20/100. Generalized hypotonia is noted at birth and is of central (brain) origin. Deep tendon reflexes are usually absent. Hypotonia may slowly improve with age, but normal motor tone and strength are never achieved. Motor milestones are delayed. Almost all affected males have some degree of intellectual disability; 10%-25% function in the low-normal or borderline range, approximately 25% in the mild-to-moderate range, and 50%-65% in the severe-to-profound range of intellectual disability. Affected males have varying degrees of proximal renal tubular dysfunction of the Fanconi type, including low molecular-weight (LMW) proteinuria, aminoaciduria, bicarbonate wasting and renal tubular acidosis, phosphaturia with hypophosphatemia and renal rickets, hypercalciuria, sodium and potassium wasting, and polyuria. The features of symptomatic Fanconi syndrome do not usually become manifest until after the first few months of life, except for LMW proteinuria. Glomerulosclerosis associated with chronic tubular injury usually results in slowly progressive chronic renal failure and end-stage renal disease between the second and fourth decades of life.

Wolf-Hirschhorn syndrome is a congenital malformation syndrome characterized by pre- and postnatal growth deficiency, developmental disability of variable degree, characteristic craniofacial features ('Greek warrior helmet' appearance of the nose, high forehead, prominent glabella, hypertelorism, high-arched eyebrows, protruding eyes, epicanthal folds, short philtrum, distinct mouth with downturned corners, and micrognathia), and a seizure disorder (Battaglia et al., 2008).

Any mitochondrial complex III deficiency in which the cause of the disease is a mutation in the UQCC3 gene.

NELABA is a severe autosomal recessive metabolic disorder characterized by onset at birth of progressive encephalopathy associated with increased serum lactate. Affected individuals have little or no psychomotor development and show brain abnormalities, including cerebral atrophy, cysts, and white matter abnormalities. Some patients die in infancy (summary by Habarou et al., 2017).

Rajab interstitial lung disease with brain calcifications-2 (RILDBC2) is an autosomal recessive disorder characterized by growth delay, interstitial lung disease, liver disease, and abnormal brain MRI findings, including brain calcifications and periventricular cysts (Krenke et al., 2019). For a discussion of genetic heterogeneity of RILDBC, see RILDBC1 (613658).

Bachmann-Bupp syndrome (BABS) is characterized by a distinctive type of alopecia, global developmental delay in the moderate to severe range, hypotonia, nonspecific dysmorphic features, behavioral abnormalities (autism spectrum disorder, attention-deficit/hyperactivity disorder) and feeding difficulties. Hair is typically present at birth but may be sparse and of an unexpected color with subsequent loss of hair in large clumps within the first few weeks of life. Rare findings may include seizures with onset in later childhood and conductive hearing loss.

Neurodevelopmental disorder with intracranial hemorrhage, seizures, and spasticity (NEDIHSS) is an autosomal recessive disorder characterized by prenatal or neonatal onset of intracranial hemorrhage, usually with ventriculomegaly and calcifications, resulting in parenchymal brain damage. Some affected individuals have symptoms incompatible with life and die in utero. Those that survive show profound global developmental delay with almost no motor or cognitive skills, hypotonia, spasticity, and seizures. Other features may include facial dysmorphism, retinal vascular abnormalities, and poor overall growth. The pathogenesis of the disease likely results from dysfunction of vascular endothelial cells in the brain (Lecca et al., 2023).