Rickets is a disease of growing bone that occurs in children due to failure of mineralization of the osteoid matrix

Rickets is a disease of growing bone that occurs in children due to failure of mineralization of the osteoid matrix. The condition specifically affects the growth plates (physes) and the newly formed bone, leading to skeletal deformities and impaired growth. While the condition is most commonly associated with vitamin D deficiency, it can result from any process that disrupts the normal deposition of calcium and phosphate in bone tissue. The term "rickets" comes from the Old English word "wrickken," meaning to twist, aptly describing the bowed deformities characteristic of the disease.

Epidemiology
Rickets has experienced a resurgence in recent decades, even in developed nations, due to changing lifestyles, increased indoor activities, cultural practices of covering skin, and exclusive breastfeeding without supplementation. The condition remains a significant public health problem in many developing countries. Infants and young children between 6 and 24 months are most susceptible because this period represents the phase of most rapid skeletal growth. Premature infants, dark-skinned individuals, and those with limited sun exposure face the highest risk.

Etiology and Classification
Rickets can be classified into two major categories: calcipenic and phosphopenic.

Calcipenic Rickets results from deficiency of calcium available for mineralization. This category includes:

Nutritional vitamin D deficiency (most common worldwide)

Defects in vitamin D metabolism (vitamin D-dependent rickets type I, caused by 1-alpha-hydroxylase deficiency)

Vitamin D receptor mutations (vitamin D-dependent rickets type II, also called hereditary resistant rickets)

Calcium deficiency (dietary, without vitamin D deficiency)

Phosphopenic Rickets results from inadequate phosphate availability and includes:

X-linked hypophosphatemic rickets (most common hereditary form, caused by PHEX gene mutations leading to increased FGF23)

Autosomal dominant hypophosphatemic rickets

Hereditary hypophosphatemic rickets with hypercalciuria

Tumor-induced osteomalacia (rare in children)

Fanconi syndrome and other renal phosphate wasting disorders

Pathophysiology
The fundamental defect in rickets is inadequate mineralization of cartilage and osteoid. The process of endochondral ossification becomes disrupted at the growth plate. Normally, chondrocytes in the growth plate proliferate, hypertrophy, and undergo apoptosis, leaving behind a cartilaginous matrix that becomes mineralized and serves as a scaffold for new bone formation.

In vitamin D deficiency, decreased intestinal absorption of calcium leads to hypocalcemia, which stimulates parathyroid hormone secretion. Parathyroid hormone acts to normalize serum calcium by increasing bone resorption and enhancing renal calcium reabsorption, but it also increases renal phosphate excretion. The resulting hypophosphatemia is critical because adequate phosphate concentrations are necessary for chondrocyte apoptosis and matrix mineralization. Without sufficient phosphate, hypertrophic chondrocytes accumulate, the growth plate widens, and the metaphysis becomes disorganized and weak.

The expanded, poorly mineralized growth plate produces the characteristic radiographic findings of cupping, fraying, and splaying. Weight-bearing forces on these weakened bones cause characteristic deformities such as bowing of the legs.

Clinical Manifestations
The clinical presentation of rickets varies depending on the severity and duration of deficiency, as well as the age of the child.

Skeletal Manifestations:

Craniotabes is often the earliest sign, appearing in the first few months of life. It manifests as softening of the skull bones, particularly along the suture lines and over the occiput. When pressed firmly, the bone indents like a ping-pong ball and springs back when released. This occurs because the outer table of the skull fails to mineralize properly.

Frontal bossing develops as compensatory new bone formation occurs beneath the periosteum of the frontal and parietal bones, creating a squared-off or "hot cross bun" appearance of the skull. This represents the body's attempt to strengthen the weakened skull.

Delayed fontanelle closure occurs because membranous bone formation at the suture margins is impaired. The anterior fontanelle may remain patent beyond 18 months of age.

Rachitic rosary describes the palpable enlargement of the costochondral junctions of the ribs. These enlargements resemble a string of beads along the anterolateral chest wall. Unlike the scorbutic rosary of scurvy, which results from hemorrhage, the rachitic rosary represents widening of the unmineralized growth plate cartilage.

Harrison's groove appears as a horizontal depression along the lower border of the chest, corresponding to the attachment of the diaphragm. The weakened ribs are pulled inward by the diaphragmatic attachments during inspiration, creating this deformity.

Pectus carinatum (pigeon chest) may develop as the softened sternum is pushed forward by the pull of the diaphragm.

Widening of the wrists and ankles results from accumulation of unmineralized osteoid at the metaphyses, creating palpable and visible enlargement of these joints.

Bowing deformities of the lower extremities are among the most recognizable signs. In infants just beginning to walk, genu varum (bowlegs) is common. In older children, genu valgum (knock-knees) may develop. The type of deformity depends on the predominant stresses applied to the growing bones.

Vertebral changes include scoliosis and kyphosis due to softening of the vertebral bodies. Compression fractures may occur in severe cases.

Dental manifestations include delayed tooth eruption, enamel hypoplasia, and increased susceptibility to dental caries. The enamel defects result from impaired mineralization of dentin.

Systemic Manifestations:

Hypocalcemic symptoms may occur in acute phases, particularly during periods of rapid growth or intercurrent illness. These include irritability, jitteriness, tetany (carpopedal spasm), laryngospasm, and seizures. Chvostek sign (facial muscle twitching upon tapping the facial nerve) and Trousseau sign (carpopedal spasm induced by forearm ischemia) may be positive.

Muscle weakness (hypotonia) is common, particularly affecting the proximal muscles. This contributes to the characteristic waddling gait and delayed motor milestones. Children often have difficulty rising from a sitting position or climbing stairs.

Growth retardation results from both the direct effects on bone and the systemic effects of chronic illness.

Increased susceptibility to infections has been observed, possibly related to the immunomodulatory effects of vitamin D.

Radiographic Findings
Radiography is essential for diagnosis and assessment of severity. The most characteristic changes appear at the metaphyses of rapidly growing bones, particularly the distal femur, proximal tibia, distal radius, and ulna.

Early changes include loss of the zone of provisional calcification, which normally appears as a thin white line at the metaphysis. This line becomes hazy, irregular, and eventually disappears.

As disease progresses, the metaphysis widens and develops a cupped or concave appearance. The margins become frayed, irregular, and indistinct (metaphyseal fraying). The distance between the epiphysis and metaphysis increases due to accumulation of unmineralized cartilage (widened growth plate).

The epiphyses, when present, appear smaller than expected and have indistinct margins (delayed and irregular ossification).

Generalized osteopenia (reduced bone density) is evident throughout the skeleton.

Looser zones (pseudofractures) may appear in the shafts of long bones as linear lucencies representing unmineralized osteoid seams.

In healing rickets, the first sign is the appearance of a thin, white line of calcification at the metaphysis (the "healing line" or "zone of preparatory calcification"), representing mineralization of the hypertrophied chondrocytes.

Laboratory Findings
Laboratory abnormalities vary depending on the underlying cause and the stage of disease.

In classic nutritional vitamin D deficiency rickets:

Serum calcium may be low, normal, or (rarely) elevated

Serum phosphate is typically low (due to secondary hyperparathyroidism)

Alkaline phosphatase is markedly elevated (reflecting increased osteoblast activity)

Parathyroid hormone is elevated (secondary hyperparathyroidism)

25-hydroxyvitamin D is low (defining vitamin D deficiency)

1,25-dihydroxyvitamin D may be low, normal, or even elevated (due to PTH stimulation)

Urinary calcium is low (due to PTH-mediated reabsorption)

Urinary phosphate is elevated (due to PTH-mediated wasting)

In calcium deficiency rickets (without vitamin D deficiency), 25-hydroxyvitamin D levels are normal.

In X-linked hypophosphatemic rickets:

Serum calcium is normal

Serum phosphate is low

Alkaline phosphatase is elevated

PTH is normal or mildly elevated

1,25-dihydroxyvitamin D is inappropriately normal or low (despite hypophosphatemia)

FGF23 levels are elevated

Urinary phosphate wasting is present (low TmP/GFR)

In vitamin D-dependent rickets type I (1-alpha-hydroxylase deficiency):

25-hydroxyvitamin D levels are normal

1,25-dihydroxyvitamin D levels are low

Other findings resemble nutritional rickets

In vitamin D-dependent rickets type II (receptor defect):

25-hydroxyvitamin D levels are normal

1,25-dihydroxyvitamin D levels are markedly elevated

Alopecia is often present

Other findings resemble nutritional rickets

Differential Diagnosis
The differential diagnosis of rickets includes:

Blount disease (tibia vara) – presents with bowing but normal laboratory studies and radiographic changes confined to the proximal tibia

Metaphyseal chondrodysplasia – genetic disorders affecting the metaphyses without biochemical abnormalities

Hypophosphatasia – low alkaline phosphatase with elevated substrates (pyridoxal-5'-phosphate, phosphoethanolamine)

Skeletal dysplasias – various genetic disorders of bone formation

Renal osteodystrophy – associated with chronic kidney disease

Osteogenesis imperfecta – brittle bones with blue sclerae and normal mineral metabolism

Treatment
Treatment depends on the underlying cause.

Nutritional Vitamin D Deficiency Rickets:

Treatment consists of vitamin D replacement and ensuring adequate calcium intake. Various regimens exist:

High-dose therapy: 150,000-600,000 IU of vitamin D given orally over 1-5 days (stoss therapy) or

Daily therapy: 2,000-5,000 IU of vitamin D daily for 6-12 weeks

Calcium supplementation (30-75 mg/kg/day of elemental calcium) should be provided during the initial treatment phase to prevent "hungry bone syndrome" (hypocalcemia as bones rapidly take up calcium during healing).

Following correction, maintenance therapy of 400 IU daily is continued.

Calcium Deficiency Rickets:

Treatment consists of calcium supplementation (30-75 mg/kg/day) without vitamin D, though vitamin D should be normalized to optimize calcium absorption.

X-Linked Hypophosphatemic Rickets:

Treatment requires combined oral phosphate (20-60 mg/kg/day divided in 4-5 doses) and calcitriol (20-30 ng/kg/day). Frequent monitoring is essential to prevent nephrocalcinosis from hypercalciuria and hyperphosphaturia.

Vitamin D-Dependent Rickets Type I:

Treatment requires lifelong calcitriol replacement (0.25-2.0 mcg daily), as these patients cannot convert 25-OH-D to the active hormone.

Vitamin D-Dependent Rickets Type II:

Treatment is challenging due to end-organ resistance. Very high doses of calcitriol or calcium infusions may be required. Some cases respond to high-dose calcium therapy.

Prevention
Prevention strategies include:

Universal vitamin D supplementation for all infants (400 IU daily from birth)

Ensuring adequate vitamin D in pregnant and lactating women (600-2000 IU daily)

Encouraging safe sun exposure

Fortification of foods with vitamin D

Screening high-risk populations

SCURVY
Definition and Overview
Scurvy is a disease resulting from prolonged deficiency of ascorbic acid (vitamin C). Unlike most animals, humans lack the enzyme L-gulonolactone oxidase required for the final step of vitamin C synthesis and therefore depend entirely on dietary intake. Vitamin C is an essential micronutrient that serves as a cofactor for numerous enzymatic reactions, particularly those involved in collagen synthesis. The disease has been recognized since ancient times but became infamous during the age of sail when sailors developed the condition during long voyages without fresh fruits and vegetables.

Epidemiology
While scurvy is now uncommon in developed countries, it persists in specific at-risk populations. In the pediatric population, scurvy typically affects:

Infants fed exclusively cow's milk without supplementation (cow's milk contains only about one-third the vitamin C of human milk and loses additional content during processing)

Children with restrictive diets due to autism spectrum disorders or severe food allergies

Children with severe malnutrition or neglect

Children on ketogenic diets for epilepsy

Children with malabsorptive conditions (cystic fibrosis, inflammatory bowel disease, celiac disease)

Toddlers with the classic "toddler's scurvy" from a diet of only milk and crackers

The classic "infantile scurvy" (Barlow disease) typically presents between 6 and 12 months of age, when maternal vitamin C stores are exhausted and the infant's diet lacks adequate supplementation.

Biochemistry and Physiology of Vitamin C
Vitamin C (ascorbic acid) is a water-soluble vitamin that functions as a reducing agent and cofactor. Its physiological roles include:

Collagen Synthesis: Vitamin C is an essential cofactor for prolyl hydroxylase and lysyl hydroxylase, enzymes that hydroxylate proline and lysine residues in procollagen. Hydroxyproline is necessary for the triple helix structure of collagen to be stable at body temperature, while hydroxylysine is required for cross-linking and glycosylation of collagen. Without hydroxylation, the unstable collagen triple helix cannot form properly, leading to the production of structurally deficient collagen that is prone to degradation and cannot provide adequate tensile strength to tissues.

Carnitine Synthesis: Vitamin C is a cofactor for enzymes involved in carnitine biosynthesis. Carnitine is essential for transport of long-chain fatty acids into mitochondria for beta-oxidation. Deficiency contributes to fatigue and muscle weakness.

Neurotransmitter Synthesis: Vitamin C participates in dopamine beta-hydroxylase activity, converting dopamine to norepinephrine. It also influences tyrosine metabolism.

Antioxidant Function: Vitamin C is a potent water-soluble antioxidant that protects cells from oxidative damage by reactive oxygen species.

Iron Absorption: Vitamin C enhances intestinal absorption of non-heme iron by reducing ferric iron (Fe³⁺) to the more absorbable ferrous form (Fe²⁺).

Gene Expression: Vitamin C influences expression of various genes through epigenetic mechanisms, as it is a cofactor for TET enzymes involved in DNA demethylation.

Pathophysiology
The fundamental defect in scurvy is the inability to synthesize and maintain normal connective tissues due to impaired collagen production. The lack of hydroxyproline and hydroxylysine results in the production of unstable, underhydroxylated collagen that cannot form proper triple helices or cross-link effectively. This abnormal collagen is more susceptible to degradation and cannot provide adequate structural support.

The consequences of this defect manifest throughout the body:

Blood Vessels: Capillary fragility results from inadequate collagen in basement membranes and perivascular tissues. This leads to spontaneous hemorrhage, particularly in areas subject to mechanical stress or minor trauma. Perifollicular hemorrhages are characteristic because hair follicles are richly vascularized and subject to movement.

Bone: The skeletal manifestations are particularly prominent in growing children. Osteoblasts normally produce osteoid (unmineralized bone matrix), which requires proper collagen for structural integrity. In scurvy, osteoblasts continue to produce osteoid, but it is abnormal and cannot mineralize properly. Meanwhile, normal bone resorption continues, leading to progressive weakening.

At the growing ends of bones (metaphyses), the histological changes are characteristic. The zone of provisional calcification, normally a thin line of calcified cartilage, becomes dense and widened (the "white line of Frankel"). Immediately adjacent to this, toward the diaphysis, there is a zone of rarefaction (the "scurvy line") where poorly formed bone has been resorbed. The weakened metaphysis is prone to microfractures and hemorrhage, leading to separation and displacement of the epiphysis in severe cases.

Subperiosteal hemorrhages occur because the periosteum, though loosely attached in children, contains blood vessels that rupture easily. Blood accumulates beneath the periosteum, elevating it from the underlying bone and causing extreme pain.

Teeth: Odontoblasts, which produce dentin, require vitamin C. Deficiency leads to defective dentin formation and hemorrhagic tendencies in the pulp and gingiva.

Wound Healing: Collagen synthesis is essential for wound repair, and deficiency leads to failure of wounds to heal and dehiscence of old scars.

Clinical Manifestations
The clinical presentation of scurvy evolves over weeks to months of deficiency. Symptoms typically appear after 1-3 months of inadequate vitamin C intake (when body stores of approximately 1500 mg are depleted).

Early Symptoms (often nonspecific):

Irritability and fussiness

Anorexia and poor weight gain

Low-grade fever

Tachypnea (possibly related to pain or metabolic abnormalities)

Failure to thrive

Specific Manifestations:

Cutaneous Manifestations:

Perifollicular hemorrhages represent the earliest specific cutaneous sign. These appear as tiny petechiae surrounding hair follicles, most prominently on the thighs and buttocks. As deficiency progresses, these hemorrhages enlarge and coalesce.

Corkscrew hairs develop due to follicular hyperkeratosis and hemorrhage around the hair follicles, causing the hairs to become coiled and fragmented.

Ecchymoses (bruises) appear spontaneously or after minor trauma, often on the lower extremities.

Poor wound healing and dehiscence of old scars may occur.

Musculoskeletal Manifestations:

Bone pain is one of the most distressing symptoms, often described as deep and aching. In infants and young children, this manifests as pseudoparalysis—the child refuses to move the affected extremity because movement exacerbates the pain. The legs are most commonly affected, leading to refusal to bear weight or walk. The child may assume the "frog leg" position with hips flexed and externally rotated to minimize discomfort.

Tenderness to palpation is marked, particularly along the shafts of long bones where subperiosteal hemorrhages have occurred.

Swelling may be visible over affected bones due to subperiosteal hemorrhage and soft tissue edema.

The scorbutic rosary appears as palpable enlargement of the costochondral junctions. Unlike the rachitic rosary, which results from widened growth plates, the scorbutic rosary results from displacement of the sternum and costal cartilages due to fractures and hemorrhages at the costochondral junctions. The step-off is often more angular and less smooth than in rickets.

Oral Manifestations:

Gingival changes are prominent in children who have erupted teeth. The gums become swollen, boggy, and spongy, with a reddish-purple or bluish discoloration. They bleed easily with minimal trauma, such as during tooth brushing or eating. In severe cases, the gums may become necrotic and ulcerated, and teeth may loosen.

In edentulous infants, gingival changes are minimal or absent.

Ocular Manifestations:

Hemorrhages may occur in the conjunctiva, eyelids, or orbit. In severe cases, proptosis (bulging of the eye) may result from orbital hemorrhage.

Systemic Manifestations:

Anemia is common and may be multifactorial: blood loss from hemorrhages, impaired iron absorption, concomitant deficiencies (particularly iron and folate), and altered hematopoiesis. The anemia is often normocytic or macrocytic, with features of both blood loss and nutritional deficiency.

Fever may occur, possibly related to cytokine release from tissue breakdown or superimposed infection.

Edema of the lower extremities may develop due to capillary leakage and hypoalbuminemia.

Cardiomegaly and electrocardiographic changes have been described in severe cases, possibly due to myocardial involvement.

Neuropsychiatric manifestations include irritability, depression, and (in advanced cases) confusion and altered consciousness.

Radiographic Findings
The skeletal radiographs in infantile scurvy are characteristic and often diagnostic. The most striking changes occur at the knees (distal femur and proximal tibia), wrists, and costochondral junctions.

Early Changes:

Osteopenia (generalized decreased bone density)

Thinning of the cortex

Prominent trabecular pattern

Advanced Changes:

The Frankel line (white line of Frankel) appears as a dense, broad white line at the metaphysis, representing the zone of provisional calcification that has become thickened and dense due to continued calcification of cartilage despite failure of bone formation.

Immediately adjacent to this, on the shaft side, is the scurvy line (Trümmerfeld zone), a transverse lucent band representing the zone of rarefaction where poorly formed bone has been resorbed.

At the corners of the metaphysis, Pelkan spikes may be seen—peripheral projections of bone resulting from healing microfractures and subperiosteal new bone formation.

Wimberger ring sign refers to a thin, sclerotic rim surrounding the epiphyseal ossification centers, which appear centrally lucent due to demineralization. The distal femoral epiphysis typically shows this finding.

Subperiosteal elevations become visible when hemorrhages calcify during healing. Initially, the elevated periosteum may not be visible, but as the hematoma organizes and calcifies, a sheath of new bone forms around the original shaft, creating the appearance of a bone within a bone.

Metaphyseal fractures may occur through the weakened zone of rarefaction, leading to separation of the epiphysis and metaphysis (corner sign or corner fracture). These appear as small, angular fragments at the metaphyseal corners.

In the chest, the scorbutic rosary appears as widening and irregularity at the costochondral junctions, sometimes with visible fractures or displacements.

Laboratory Findings
No single laboratory test definitively diagnoses scurvy, though certain findings support the diagnosis:

Serum ascorbic acid level: Low (<0.2 mg/dL indicates deficiency; <0.1 mg/dL confirms scurvy). However, this reflects recent intake rather than tissue stores.

Leukocyte vitamin C level: More accurately reflects tissue stores but is technically difficult to perform.

Anemia: Present in 75-80% of cases, often normocytic or macrocytic.

Hypoalbuminemia: May occur due to poor nutrition.

Elevated erythrocyte sedimentation rate: Reflects inflammation and tissue breakdown.

Urinalysis: May show hematuria (microscopic or gross).

Coagulation studies: Normal (distinguishing from coagulation disorders).

Differential Diagnosis
The differential diagnosis of scurvy includes:

Rickets: Presents with similar bone pain and irritability but with different radiographic findings (cupping, fraying) and laboratory abnormalities (elevated alkaline phosphatase, abnormal calcium/phosphate). The rosary in rickets is smoother and less angular.

Osteomyelitis: Presents with focal bone pain, fever, and swelling but without the diffuse involvement or cutaneous findings of scurvy.

Leukemia or metastatic neuroblastoma: May present with bone pain, anemia, and irritability. Bone marrow examination and imaging help distinguish.

Juvenile idiopathic arthritis: Presents with joint swelling and pain but without the characteristic radiographic changes.

Henoch-Schönlein purpura: Presents with palpable purpura and arthralgia but without bone changes.

Coagulation disorders: Present with bleeding but have abnormal coagulation studies and lack bone changes.

Child abuse: May present with fractures and bruising, requiring careful evaluation of the social context and presence of other signs of scurvy.

Treatment
Treatment of scurvy is straightforward and highly effective:

Vitamin C Replacement:

Infants and young children: 100-300 mg daily orally

Older children: 500-1000 mg daily orally for the first week, then 100-300 mg daily until full recovery

Intravenous administration may be necessary in severe cases with malabsorption or critical illness.

Supportive Care:

Pain management during the initial treatment phase (NSAIDs or acetaminophen)

Gentle handling to avoid pain from movement

Nutritional support to address concomitant deficiencies (iron, folate, other vitamins)

Dental care for gingival involvement

Physical therapy as pain resolves

Response to Treatment:

Clinical improvement is often dramatic. Within 24-48 hours, irritability decreases, pain improves, and the child becomes more comfortable. Fever resolves within days. Gingival bleeding stops within days to weeks. Bone tenderness resolves over 1-2 weeks. Radiographic healing begins within weeks, with calcification of subperiosteal hemorrhages visible by 2-3 weeks.

Prevention
Prevention of scurvy requires ensuring adequate vitamin C intake:

Infants: Breast milk provides adequate vitamin C if the mother's intake is sufficient (approximately 40 mg/day in breast milk). Formula is fortified with vitamin C.

Children: 15-45 mg daily depending on age, easily achieved through dietary sources.

Good dietary sources: Citrus fruits, strawberries, kiwi, melon, tomatoes, bell peppers, broccoli, potatoes, and fortified foods.

For at-risk populations (children with restrictive diets, malabsorption, or on specialized diets), supplementation should be considered.

Key Distinctions Between Rickets and Scurvy
While both conditions affect growing children and may present with irritability, bone pain, and failure to thrive, important distinctions exist:

Feature Rickets Scurvy
Deficiency Vitamin D Vitamin C
Primary defect Mineralization failure Collagen synthesis failure
Age of presentation 6-24 months 6-12 months (infantile)
Bony changes Widened, cupped metaphyses Dense white line + lucent band
Rosary Smooth, rounded enlargement Angular, step-off deformity
Bleeding manifestations Uncommon (except hypocalcemic) Prominent (gums, skin, subperiosteal)
Gingiva Normal (unless teeth erupting) Swollen, purple, bleeding
Calcium/Phosphate Abnormal Normal
Alkaline phosphatase Markedly elevated Normal or mildly elevated
Response to specific therapy Weeks to months Days to weeks
Historical Perspective
Rickets was first described by physicians in the 17th century, with Francis Glisson publishing "De Rachitide" in 1650. The industrial revolution saw a dramatic increase in rickets due to urban pollution blocking sunlight and crowded living conditions. The discovery that cod liver oil could prevent and cure rickets in the early 20th century, followed by the identification of vitamin D and the fortification of milk, led to a dramatic decline in the developed world.

Scurvy has been recognized since ancient times, with Hippocrates describing symptoms resembling the disease. The devastating impact of scurvy on long sea voyages is legendary, with Vasco da Gama losing two-thirds of his crew to the disease in 1499. In 1747, James Lind conducted one of the first controlled clinical trials, demonstrating that citrus fruits cured scurvy, though it took another 40 years for the British navy to adopt lemon juice as standard issue. Albert Szent-Györgyi isolated vitamin C in 1928, for which he received the Nobel Prize in 1937.

Both diseases, though now easily preventable and treatable, continue to appear in clinical practice and require a high index of suspicion for diagnosis. Their persistence serves as a reminder of the ongoing importance of nutrition in child health and development.